1 . .

NEW YORK UNI V E R S I T Y

COLLEGE OF ENGINEERING RESEARCH D i v r s i o ~ 4 ,

NY-9'55

THERMODYNAMIC PROPERTIES OF B I N A R Y

IRON - ALUMINUM ALLOYS

B Y

J . ELDRiDGE AND K. KOMAREK

FINAL REPORT

ON

CONTRACT No. DA-30-069-ORD-2009 ORDNANCE R & D No . TB2-0001

D A PROJECT No . 5-99-01-004 OOR PROJECT No . 1939

DECEMBER I960

s

OFFICE OF ORDNANCE RESEARCH UNITED STATES ARMY

B o x CM, DUKE STATION DURHAM, NORTH CAROLINA

DISCLAIMER

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency Thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

DISCLAIMER Portions of this document may be illegible in electronic image products. Images are produced from the best available original document.

c

CONTRACT No. DA-30-069-ORD-2009 ORDNANCE R & D No. TB2-0001

DA PROJECT NO. 5-99-01-004 OOR PROJECT No. 1939

DECEMBER I 960

THERMODYNAMI C PROPERT I ES OF B I NARY IRON - ALUMINUM ALLOYS

7 FINAL REPORT B Y J. ELDRIDGE AND K. KOMAREK

I

A B S T R A C T : A METHOD HAS B E E N D E V E L O P E D T O E Q U I L I B R A T E M E T A L S P E C I M E N S I N AN A L L C E R A M I C S Y S T E M W I T H A R E A C T I V E LOW M E L T I N G M E T A L OF LOW V O L A T I L I T Y . R E L A T I V E L Y FEW EXPERIMENTS ARE N E C E S S A R Y

A WIDE RANGE OF T E M P E R A T U R E AND C O N C E N T R A T I O N . THERMODYNAMIC

B Y THIS METHOD BETWEEN 30 AND 75 ATOMI c $ ALUMINUM AND I 100 T O 1400°K. THE A C T I V I T Y OF ALUMINUM SHOWS A STRONG NEGATIVE D E V I A T I O N FROM RAOULT 'S L A W AT LOW C O N C E N T R A T I O N S OF ALUMINUM BUT INCREASES R A P I D L Y ABOVE 40 ATOMIC $ ALUMINUM. CLOSE T O 50 ATOMI c $ ALUMINUM THE B E H A V I O R OF THERMODYNAMI c PROPERT I E S INDICATES A R A P I D I N C R E A S E I N ORDER A S THE COMPOSITION FEAL

ALUMINUM OCCURS AT THE INTERMETALLIC COMPOUND FEAL . VARIOUS MOLAR AND P A R T i a L MOLAR THERMODYNAMi c PROPERT 1 E S H 2 v E B E E N CALCULATED FOR A TEMPERATURE OF 1200'K. THE A C C U R A C Y AND

T O O B T A I N R E L I A B L E R E S U L T S OF THERMODYNAMIC PROPERT I E S OVER

P R O P E R T I E S O F S O L I D I R O N - A L U M I N U M A L L O Y S H A V E B E E N D E T E R M I N E D

I S APPROACHED. A FURTHER R A P I D I N C R E A S E O F T H E A C T I V I T Y OF

R E L I A B I L I T Y O F T H E R E S U L T S H A S B E E N A S S E S S E D AND T H E R E S U L T S COMPARED W I T H P U B L I S H E D D A T A .

THIS WORK SPONSORED BY THE OFFICE OF ORDNANCE RESEARCH WAS CARRIED OUT

B Y NEW YORK UNIVERSITY COLLEGE OF ENGINEERING RESEARCH DIVISION.

I 1

1-

h 'd

-'

TABLE OF CONTENTS

PAGE

1 . INTRODUCTION. o e o o 4 o o o o o o e e a o o e I

I I . APPARATUS AND EXPERIMENTAL PROCEDURE . . . . . 4 A. M A ' T E R I A L S e . . e . . . . 4

C, EXPERIMENTAL PROCEDURE . e e e e 8

1 1 1 . EVAL.UATION OF EXPERIMENTAL RESULTS . . . e . II

I V . EXPERIMENTAL RESULTS . . . . a . e . . . 17

V. E R R O R S . . . . . . . , . . . . . . . . . . . . . . . . . 22

V I . DISCUSSION AND CONCLUSION . . . . . e . 28

V I I I . REFERENCES . e . . . a . I . e 33 TA6LES AND I LLUS'TRAT IONS FOLLOW PAGE 34

i

LIST OF TABLES

.=' V'

c

TABLE

1 .

I I .

1 1 1 .

I V .

V.

VI.

V I I .

V I I I .

I x.

-

X .

PAGE - RUN I ( A L U M I N U M - S O D I U M C H L O R I D E ) e e . . 35

RUN 3 ( A L U M I N U M ) e e . . L) . . . 36

RUN I - K ( A L U M I N U M - S O D I U M C H L O R I D E ) e . . . 37

RUN I -N ( A L U M I N U M ) . . e . . (I e (I . . 38

RUN 1-0 ( A L U M I N U M ) . e . ., e e . 39 RUN I - P ( A L U M I N U M ) e (I . . . . . 40

RUN I -R ( A L U M I N U M ) . . e e e . . 41

RUN I-S (ALUMINUM-SODIUM C H L O R I D E ) e e e . (1 . . 42

R E L A T I VE P A R T I A& MOLAR ENTHALPY OF A L U M I N U M AH,^) e e (I . e . 43 THERMODYNAMIC P R O P E R T I E S O F I R O N - ALUMINUM A L L O Y S AT 1200°K . e (I . (1 . 44

i

I V

LIST OF ILLUSTRATIONS

F I GURE h E

v' 1 . IRON-ALUMINUM P H A S E DIAGRAM

2. IRON REACTION TUBE WITH POSITIONED SPECIMENS PRIOR T O FINAL ASSEMBLY AND WELDI NG

'c 3. UNIT FOR ARC WELDING IRON REACTION TUBES

4. ALUMI N A REACT I ON Tuef (BE FORE MELT I NO ALUMINUM)

5 . 6. ACTIVITY OF ALUMINUM AS A FUNCTION O F C O M P O S I T I O N AS

ALUMINA REACTI ON TUBE ( A F T E R MELT I NO ALUMINUM)

DETERMINED B Y EXPERIMENTAL RUNS I N IRON REACTION TUBES

A C T I V I T Y OF ALUMINUM A S A FUNCTION O F C O M P O S I T I O N AS DETERMINED B Y EXPERIMENTAL RUNS I N ALUMINA REACTION TUBES

A C T I V I T Y OF ALUMINUM I N IRON-ALUMINUM ALLOYS FROM 30 T O 100 ATOMIC PERCENT ALUMINUM

7.

8.

9. A C T I V I T Y OF ALUMINUM I N IRON-ALUMINUM ALLOYS FROM 0 T O 50 ATOMIC PERCENT ALUMINUM

IO. A C T I V I T Y COEFFICIENTS OF ALUMINUM IN IRON-ALUMINUM A L L O Y S FROM 0 TO 50 ATOMIC PERCENT ALUMINUM

I I . THERMODYNAMI c PROPERT I E S OF I RON-ALUMI NUM ALLOYS AT 1200'K

12. MOLAR AND PARTIAL MOLAR ENTROPY OF IRON-ALUMINUM ALLOYS A T 1200'K

r

f

n V

I . I NTRODUCT I ON

r

i

i

THE IRON-ALUMINUM SYSTEM I S OF BOTH THEORETICAL AND P R A C T I C A L

I N T E R E S T FOR V A R I O U S REASONS AND I T HAS B E E N T H E OBJECT OF A GREAT NUMBER

OF I N V E S T I G A T I O N S . MOST OF T H E S E S T U D I E S WERE CONCERNED W I T H T H E PHASE

D I A G R A M AND T H E ORDER-DISORDER R E A C T I O N S F I R S T OBSERVED B Y BRADLEY AND

J A Y " ) .

D I A G R A M B Y HANS EN'^) BUT T H E D E L I N E A T I O N OF S E V E R A L PHASE B O U N D A R I E S WAS

I N A RECENT STUDY LEE (3)

THE RESULTS H A V E BEEN COMPILED AND PRESENTED AS A COMPLETE PHASE

LEFT OPEN FOR FURTHER INVESTIGATIONS (FIG. I ) .

REDETERMINED THE SOLIDUS AND L I Q U I D U S C U R V E S AND FOUND T H A T FEAL (e) H A S

A CONGRUENT MELTING POINT. THE MOST PROMINENT FEATURES OF THE PHASE D I A -

3

GRAM ARE AN E X T E N S l V E RANGE O F S O L I D S O L U T I O N S OF A L U M I N U M I N a - I R O N FROM

0 T O 52 AT$ AL, A SERIES OF ORDER-DISORDER TRANSFORMATIONS AT LOWER TEMPER-

ATURES W I T H I N T H E Q - F I E L D , A N D S E V E R A L I N T E R M E T A L L I C COMPOUNDS, N A M E L Y

FEAL, F E A L ~ ' FE AL

BOTH ORDERED A N D D I S O R D E R E D A L L O Y S CAN E X I S T I N THE a - F I E L D UP T O T H E

AND FEAL RECENTLY, TAYLOR AND J O N E S ( 4 ) FOUND T H A T 2 5' 3'

SOLIDUS C U R V E SEPARATED B Y A G E N T L Y CURVED SLOPING L I N E STARTING AT 18.75

AT$ AL AT ROOM TEMPERATURE UP T O 37 AT$ AL AT 1375°C. ALLOYS W I T H I N T H E a - P H A S E F I E L D ARE OF S P E C I A L C O M M E R C I A L I N T E R -

EST. THOSE CONTAINING ABOUT 25 T O 30 AT$ AL ARE BEING INVESTIGATED FOR

USE AS H I G H Q U A L I T Y , SOFT M A G N E T I C M A T E R I A L S WHEREBY T H E O R D E R I N G REAC-

T I O N S AND T H E R E B Y T H E M A G N E T I C P R O P E R T I E S ARE C O N T R O L L E D B Y HEAT T R E A T -

MENT. DUE T O E X C E L L E N T H I G H - T E M P E R A T U R E O X I D A T I O N R E S I S T A N C E , A T T R A C T I V E

NUCLEAR P R O P E R T I E S AND LOW COST I R O N - A L U M I N U M B A S E A L L O Y S HAVE A L S O B E E N

STUD1 ED A S POSS I B L E N U C L E A R REACTOR COMPONENTS(5) I N S T E E L M A K l NG ALUM1 NUM

I S BEING USED AS A DEOXIDANT. FINALLY, I T HAS BEEN PROPOSED T O PRODUCE

- I -

89% 06

A L U M I N U M B Y C A R B O T H E R M I C R E D U C T I O N O F A L U M I N U M B E A R I N G ORE AND TO E X T R A C T

(6) A L U M I N U M FROM T H E R E S U L T I N G A L U M I N U M R I C H A L L O Y S - _- e

c

i

I N V I E W O F T H E IMPORTANCE O F T H E I R O N - A L U M I N U M S Y S T E M I T H A S

B E E N F E L T T H A T A S T U D Y O F T H E THERMODYNAMIC P R O P E R T I E S WOULD C O N T R I B U T E

M A T E R I A L L Y T O T H E U N D E R S T A N D I N G OF A L L O Y S I N T H I S S Y S T E M .

BECAUSE OF ITS USE A S A D E O X I D A N T I N THE STEEL INDUSTRY CHIPMAN

AND COWORKERS ( 7 ' 8 9 9 ' ' 0 ) H A V E S T U D I E D R E P E A T E D L Y T H E A C T I V I T Y O F A L U M I N U M

I N L I Q U I D D I L U T E IRON-ALUMINUM ALLOYS. THEY M E A S U R E D THE DISTRIBUTION

O F A L U M I N U M BETWEEN L I Q U I D I R O N AND S I L V E R AND C A L C U L A T E D T H E A C T I V I T Y

FROM KNOWN A C T I V I T Y V A L U E S O F A L U M I N U M I N S I L V E R A T SOME LOWER TEMPERA-

TURE.

WILDER AND ELLIOTT ( I 2 ) .

THE RESULTS H A V E BEEN R E C A L C U L A T E D B Y CHOU AND ELLIOTT ( ' ' ) AND

P E H L K E ( I 3 ) COMPUTED T H E A C T I V I T Y OF A L U M I N U M AT

1 6 0 0 " ~ O V E R THE WHOLE C O N C E N T R A T I O N RANGE FROM THE SLOPE OF THE LIQUIDUS

CURVE B U T NO G R E A T ACCURACY CAN B E A S S I G N E D T O H I S RESULTS, S I N C E T H E

L I Q U I D U S T E M P E R A T U R E S L A C K T H E N E C E S S A R Y P R E C I S I O N .

THERMODYNAMIC I N V E S T I G A T I O N S OF S O L I D IRON-ALUMINUM ALLOYS H A V E

B E E N R E S T R I C T E D T O T H E C A L O R I M E T R I C D E T E R M I N A T I O N O F H E A T S O F F O R M A T I O N

B Y B l L T Z AND H A A S E ( 1 4 ) , O E L S E N AND M I D D E L ( ' 5 ) , AND KUBASCHEWSKI AND

DENCH (I6). AFTER THE PRESENT I N V E S T I G A T I O N WAS I N I T I A T E D GROSS AND co-

WORKERS ( I 7 ) P R E S E N T E D T H E R E S U L T S OF T H E I R S T U D Y OF T H E A C T I V I T I E S O F

ALUMINUM I N SOL I D i RON-ALUMI NUM A L L O Y S . THE MEASUREMENTS AT 920°C WERE

C A R R I E D OUT B Y A C A P I L L A R Y METHOD DEVELOPED B Y GROSS (I8) FOR T H E S T U D Y

OF EQU I L I BR I A I N V O L V I NG ALUMI NUM MONOHAL I DES AND AT I 300"c B Y EMPLOY I NG

T H E E F F U S I O N T E C H N I Q U E .

-2-

0

THE S C A R C I T Y OF THERMODYNAMIC D A T A I N THE IRON-ALUMINUM SYSTEM

I S M A I N L Y DUE T O EXPERIMENTAL D I F F I C U L T I E S . ALUMINUM I N THE MOLTEN OR

GASEOUS S T A T E I S A VERY R E A C T I V E M E T A L W H I C H I M P O S E S SEVERE R E S T R I C T I O N S

ON THE CHOICE OF CONTAINER MATERIALS. AT LOWER TEMPERATURES ALUMJNUM HAS

A R A T H E R LOW VAPOR PRESSURE SO T H A T E V A P O R A T I O N AND E Q U I L I B R A T I O N WILL

PROCEED B U T SLOWLY. A MAJOR O B S T A C L E T O EMF-MEASUREMENTS, B E S I D E S T H E

P R O B L E M T O S E L E C T A S U I T A B L E C O N T A I N E R M A T E R I A L , C O N S I S T S I N F I N D I N G A

M O L T E N E L E C T R O L Y T E W H I C H WILL PERFORM R E V E R S I B L Y .

FROM A R E V I E W OF THE D I F F I C U L T I E S INVOLVED I T BECAME C L E A R

T H A T A NEW APPROACH H A D T O B E FOUND T O O B T A I N THERMODYNAMIC P R O P E R T I E S

IN THE IRON-ALUMINUM SYSTEM. THE SCOPE OF T H I S INVESTIGATION WAS T O

D E V E L O P A METHOD T O MEASURE A C T I V I T I E S O F A L U M I N U M I N S O L I D I R O N - A L U M I N U M

A L L O Y S OVER A N E X T E N D E D RANGE O F A L L O Y C O M P O S I T I O N I N T H E TEMPERATURE

RANGE FROM ABOUT 750°C T O IO5O"C. A TECHNIQUE WAS CHOSEN AND ADAPTED T O

THE PROBLEM WHICH HAS BEEN O R I G I N A L L Y AP,PLIED B Y HERASYMENKO ( I 9 ) T O T H E

STUDY OF THE SI LVER-CADMI UM SYSTEM. AT TEMPERATURES ABOVE ~OO"C,SPECI -

MENS WERE E Q U I L I B R A T E D W I T H A L U M I N U M VAPOR FROM AN A L U M I N U M SOURCE K E P T

AT CONSTANT TEMPERATURE IN AN E V A C U A T E D ALL ALUMINA SYSTEM. THE SPECI-

MENS WERE H E A T E D I N A TEMPERATURE G R A D I E N T U N T I L E Q U I L I B R A T I O N WAS COM-

PLETED AND THEN A N A L Y Z E D . AT TEMPERATURES BELOW 800"c SODIUM CHLORIDE

WAS ADDED U T I L I Z I N G T H E F O R M A T I O N O F A L U M I N U M S U B C H L O R I D E T O A C C E L E R A T E

T H E T R A N S F E R O F A L U M I N U M FROM T H E A L U M I N U M SOURCE T O T H E I R O N S P E C I M E N S .

THE N E C E S S A R Y EQUATIONS H A V E BEEN WORKED OUT T O OBTAIN A C T I V I T I E S OF

ALUMINUM. THE METHOD I S APPLICABLE T O OTHER SYSTEMS E S P E C I A L L Y T O ALLOYS

O F H I G H REFRACTORY M E T A L S W I T H OTHERS O F R E L A T I V E L Y LOW M E L T I N G P O I N T

AND LOW V O L A T I L I T Y

- 3- 83% 08

1 1 . APPARATUS AND EXPERIMENTAL PROCEDURE

b

A. MATERIALS:

THE IRON SPECIMENS WERE MADE FROM VACUUM MELTED IRON "FERROVAC E"

PURCHASED FROM VACUUM METALS CORP. AND ROLLED TO A .OO5" T H I C K SHEET B Y

HAMILTON WATCH Co. THE COMPOSITION I N WT WAS AS FOLLOWS: .OO9 C, ,001 MN,

.002 P, .007 S, ,006 SI, . O b NI, .01 CR, .004 V, .01 Mo, ,007 Co, . O I 4 Cu,

.OI AL, .0004 PB, .0003 N, .008 0 , .00006 H.

I RON-ALUM1 NUM SPEC I MENS WERE P R E P A R E D FROM A e o 1 " T H I C K S H E E T

OBTA I NED FROM GENERAL PLATE D I v I s I ON (METALS AND CONTROLS CORPORAT I O N )

SOLD UNDER THE TRADE NAME "ALFENOL".

AS G I V E N B Y THE SUPPLIER WAS 16.21 AL, .014 C, .0002 P, .005 S.

THE C H E M I C A L COMPOSITION I N WT $4

THE ALUMINUM USED (ALUMINUM CORP. OF AMERICA) HAD A P U R I T Y OF

METAL 99.994 AND THE SODIUM CHLORIDE WAS OF A N A L Y T I C A L GRADE ( B A K E R ) .

S P E C I M E N T U B E S AND S P A C E R S WERE M A C H I N E D FROM S O L I D ARMCO I R O N RODS

(99 .94 FE) AND HEATED FOR S E V E R A L HOURS I N WET HYDROGEN. THE ALUMINA

T U B E S AND C R U C I B L E S WERE MADE O F I M P E R V I O U S R E C R Y S T A L L I Z E D A L U M I N A W I T H

AN A L U M I N A CONTENT OF 99.$ (TRIANGLE RR, MORGANITE INC.).

8. APPARATUS:

I N I T I A L EXPERIMENTS WERE MADE I N CLOSED IRON TUBES WHILE THE

B U L K O F T H E I N V E S T I G A T I O N WAS C A R R I E D OUT U S I N G H I G H P U R I T Y A L U M I N A TUBES,

SEALED B Y A MOLTEN ALUMINUM POOL. ALTHOUGH THE PREPARATION AND ASSEMBLAGE

OF THESE TUBES D I FFERED MARKEDLY, THE EXPERI MENTAL COND I T I ONS ( E .G. TEMPER-

ATURE) WERE SIMILAR; FOR THAT REASON, THE ASSEMBLAGE OF E A C H KIND OF TUBE

WILL B E D E S C R I B E D S E P A R A T E L Y BELOW, B U T A D I S C U S S I O N O F T H E E X P E R I M E N T A L

METHOD, GERMANE T O BOTH T Y P E S OF TUBES, WILL BE PRESENTED TOGETHER. THE

M A I N C R I T E R I O N I N THE T U B E D E S I G N WAS T O P R O V I D E A C L O S E D THERMODYNAMIC

S Y S T E M I N W H I C H T H I N I R O N S P E C I M E N S , AT D I F F E R E N T P O S I T I O N S I N A TEMPER-

ATURE G R A D I E N T , COULD B E E Q U I L I B R A T E D W I T H A G A S P H A S E O F KNOWN A L U M I N U M

A C T I V I T Y R E S U L T I N G I N A D I F F U S I O N OF A L U M I N U M I N T O T H E SPECIMENS UNTIL,

I N E Q U I L I B R I U M , T H E P A R T I A L PRESSURE O F T H E A L U M I N U M I N EACH O F T H E

S P E C I M E N S E Q U A L E D T H A T OF T H E P A R T I A L PRESSURE OF T H E A L U M I N U M I N T H E

G A S P H A S E A D J A C E N T T O EACH S P E C I M E N . B Y M A I N T A I N I N G A R E S E R V O I R O F

A L U M I N U M AT T H E TEMPERATURE M I N I M U M , T H E A C T I V I T Y O F A L U M I N U M I N T H E

GASEOUS P H A S E THROUGHOUT T H E S T A T I C S Y S T E M CAN B E C A L C U L A T E D FROM A KNOW-

L E D G E OF T H E TEMPERATURE DEPENDENCE OF T H E VAPOR PRESSURE O F A L U M I N U M AND

I N THE PRESENCE OF NACL OF THE E Q U I L I B R I U M CONSTANT FOR THE REACTION,

( 4 NACL f AL = NA ( G ) + ALCL

IN RUNS WITHOUT NACL, THE A C T I V I T Y OF ALUMINUM I N A G I V E N SPECIMEN A T

(4 (4

E Q U I L I B R I U M IS E Q U A L T O T H E R A T I O O F T H E P A R T I A L PRESSURE O F A L U M I N U M I N

THE SPECIMEN (DETERMINED B Y THE AL R E S E R V O I R TEMPERATURE) T O THE V A P O R

PRESSURE O F PURE A L U M I N U M AT T H E TEMPERATURE O F T H E S P E C I M E N .

IRON REACTION TUBES

SOLID ARMCO IRON RODS, 1-1/4" D IA . x 14 T O 16" LONG, WERE

DRILLED OUT T O AN INSIDE D IAMETER OF 1 - 1 / 1 6 " ~ IRON PLUGS WERE M A C H I N E D

W I T H F L A N G E S T O CLOSE O F F T H E T U B E S A T B O T H ENDS; T H E F L A N G E S WERE MADE

T O F A C I L I T A T E SUBSEQUENT ARC-WELDING O F T H E P L U G S 'TO T H E LONG T U B E . THE

TOP PLUG ALSO HAD A CONCENTRIC I / )+ ' ' 1.D. x 3/81! O.D. FLANGE T O PERMIT A

LONG ( A P P R O X I M A T E L Y 14") IRON TUBE T O EXTEND INTO THE 1/1/4" REACTION

* TUBE. THE INNER IRON TUBE WAS CLOSED ON THE BOTTOM END BY WELDING AND:

( A ) ALLOWED ACCESS FOR A THERMOCOUPLE I N S I D E T H E R E A C T I O N TUBE; ( B ) S E R V E D v

A S A V E R T I C A L SUPPORT FOR THE SPECIMENS. THE INNER TUBE WAS MADE OF THE

LOWEST-CARBON S T E E L C O M M E R C I A L L Y A V A I L A B L E AND WAS S U B J E C T E D T O A STRONGLY

REDUCING H2-H20 G A S M I X T U R E AT I O O O ~ C FOR S E V E R A L HOURS T O LOWER THE

IMPURITY C O N T E N T . THE B O T T O M PLUG WAS PROVIDED W I T H A SHORT C A P I L L A R Y

S T E E L T U B E FOR F I N A L E V A C U A T I O N O F T H E ASSEMBLED T U B E .

1 . SPECIMEN PREPARATION. SPECIMENS WERE PREPARED FROM BOTH

I R W AND I R O N - I ~ ~ ALUMINUM ALLOY SHEET so THAT E Q U I L I B R A T I O N COULD BE

F A C I L I T A T E D B Y R E D U C I N G T H E AMOUNT O F A L U M I N U M W H I C H H A D T O B E T R A N S P O R T E D

T O T H E S P E C I M E N S .

ANNULAR SPECIMENS 12 MM I.D. x 20 MM O.D. WERE PUNCHED FROM

I R O N S H E E T 5 M I L S T H I C K AND FROM I R O N - A L U M I N U M A L L O Y S H E E T 10 M I L S T H I C K

USING A H I G H A L L O Y TOOL S T E E L D I E . THEY WERE GROUND T O REMOVE PUNCHING

BURRS, DEGREASED I N CARBON T E T R A C H L O R I D E , R I N S E D ON ACETONE AND W E I G H E D

4- ON A M I C R C ' A L A N C E T O W I T H I N A N ACCURACY OF - 0.01 MG.

IRON AND IRON-ALUMINUM A L L O Y SPECIMENS WERE A L T E R N A T E L Y P O S I -

TIONED ALONG THE INNER TUBE, USING TRIANGULAR S P A C E R S 3/81! HIGH PREPARED

FROM E L L C T R O L Y T I C IRON SHEET. THE POSITIONS OF THE SPECIMENS WITH RESPECT

t T O THE INNER TUBE WERE MEASURED T O WITHIN AN A C C U R A C Y OF - 0.5 MM. (SEE

F I G U R E 2 ) .

2. CRUCIBLES. BECAUSE LIQUID ALUMINUM I S E X T R E M E L Y R E A C T I V E ,

C R u C l J L E S O F H I G H - P U R I T Y A L U M I N A WERE USED T O C O N T A I N T H E A L U M I N U M (OR

AL-NACL MI X T U R E ) . FOR SOME RUNS H I GH-PURI T Y GRAPH ITE CRUC I BLES WERE

EMPLOYED B U T AT H I G H E R T E M P E R A T U R E S AND LONGER T I M E S O F EXPOSURE A L U M I N U M

REACTED S E V E R E L Y T O FORM ALUMINUM CARBIDE. THIN TITANIUM SHEET WAS

WRAPPED AROUND T H E G R A P H I T E COMPONENTS T O P R E V E N T I R O N - G R A P H I T E CONTACT.

SINCE THE TEMPERATURE OF THE R E S E R V O I R HAD T O BE KNOWN A C C U R A T E L Y , THE

-6-

891 I?.

d

"r

INNER I R O N T U B E WAS EXTENDED D I R E C T L Y I N T O THE M E L T AND WAS PROTECTED B Y

A S H E A T H OF E I T H E R A L U M I N A OR G R A P H I T E .

3. WELDING OPERATIONS. WITH THE EXCEPTION OF THE SEALING OF

T H E C A P I L L A R Y TUBE, ALL W E L D I N G O P E R A T I O N S WERE DONE I N AN ARGON ATMOS-

PHERE UNDER REDUCED PRESSURE I N THE S P E C I A L L Y CONSTRUCTED W E L D I N G U N I T

SHOWN I N FIGURE 3. THE PART T O BE WELDED WAS POSIT IONED WITH SCREWS I N

A S T E E L B E A K E R W H I C H COULD BE R A I S E D AND LOWERED B Y A LONG S T E E L ROD. A

W E L D I N G GENERATOR SERVED AS THE POWER SOURCE W I T H O N E POLE CONNECTED T O

T H E T U N G S T E N T I P P E D E L E C T R O D E AND THE OTHER ONE TO THE S T E E L ROD. B E F O R E

C L O S I N G THE C A P I L L A R Y TUBE, T H E R E A C T I O N TUBE WAS E V A C U A T E D AND F L U S H E D

W I T H OXYGEN S E V E R A L T IMES. THE TUBE WAS F I N A L L Y E V A C U A T E D T O 0.1 MICRON

(HG) PRESSURE AND CLOSED. TRACES OF O X Y G E N LEFT I N T H E TUBE REACTED ON

H E A T I N G W I T H A L U M I N U M AND D I D NOT CAUSE ANY I N T E R F E R E N C E DUE T O T H E R M A L

D I F F U S I O N .

THE REST OF THE PROCEDURE I S S I M I L A R FOR BOTH THE IRON AND

A L U M I N A TUBES; ACCORDINGLY, T H E C O N S T R U C T I O N OF THE L A T T E R WILL NOW BE

D I S C U S S E D BEFORE P R O C E E D I N G FURTHER.

AI U M I NA REACT I ON TUBES

ALUMINA TUBES, CLOSED AT THE TOP, WERE CONVENIENTLY AND SATIS-

FACTORILY SEALED ON THE BOTTOM ( A F T E R INSERTION OF THE SPECIMENS, E T C . )

B Y HEATING THESE INVERTED TUBES IN POOLS OF MOLTEN ALUMINUM. BECAUSE

HIGH-PURITY ALUMINA I S INERT TO LIQUID AND GASEOUS AL AT THE TEMPERATURES

USED I N T H I S STUDY, A L L COMPONENTS OF T H E R E A C T I O N T U B E WERE O F RECRYS-

T A L L I Z E D H I G H - P U R I T Y A L U M I N A .

I RON AND I RON-I 6% ALUM1 NUM A L L O Y SPEC I MENS, PREPARED AS P R E V I -

OUSLY DESCRIBED, WERE ALTERNATELY POSITIONED ALONG A 1/4" D I A . ALUMINA TUBE.

- 7-

SPACERS OF ALUMINA, 1/2" T O 3/41' HIGH x 3/8" I.D. x 1 / 2 o.D., WERE USED

3

T O S E P A R A T E AND P O S I T I O N T H E S P E C I M E N S AND T H E P O S I T I O N S O F T H E S P E C I M E N S

WITH RESPECT T O THE R E A C T I O N TUBE WERE MEASURED. HIGH-PURITY ALUMINUM

METAL WE I GH I NG APPROX I M A T E L Y 80 GRAMS WAS MACH I NED T O THE C Y L I NDR I C A L

SHAPE SHOWN I N FIGURE 4. SODIUM CHLORIDE, D R I E D FOR S E V E R A L HOURS AT 5oo0c., WAS PLACED ON TOP OF

IN RUNS W I T H NACL A P P R O X I M A T E L Y 8-10 GRAMS OF

THE ALUMINUM.

H I G H AND A I " I.D. x 1-1/4" O.D. x 14 T O 16" ALUMINA TUBE ( C L O S E D ON THE

TOP END) WERE ASSEMBLED WITH THE SPECIMENS AS SHOWN I N FIGURE 4.

AN A L U M I N A CRUCl6LE l - l / z l ' 1.D. X 1-9/1611 0.D. X 3-1/2"

THE ADVANTAGES OF T H I S ARRANGEMENT ARE THE FOLLOWING:

A. THE CONTENTS OF THE R E A C T I O N TUBE C A N BE THOROUGHLY D R I E D

I N S I T U I N VACUUM AND A T TEMPERATURES UP T O T H E M E L T I N G

POINT OF ALUMINUM, I . E . 6 5 9 " ~ . THIS W I L L REMOVE A N Y T R A C E S

OF MOISTURE PICKED UP B Y NACL D U R I N G TUBE ASSEMBLY, WHICH

COULD CAUSE U N D E S I R A B L E S I D E R E A C T I O N S I F NOT REMOVED.

B. THE MOLTEN ALUMINUM A C T S S A T I S F A C T O R I L Y A S A SEALANT T O

I S O L A T E T H E CONTENTS O F THE T U B E FROM T H E SURROUNDINGS.

C. THE USE OF A R E L A T I V E L Y LARGE Q U A N T I T Y OF ALUMINUM PRODUCES

A F L A T T E R TEMPERATURE M I N I M U M SO T H A T T H E TEMPERATURE O F

THE AL-NACL INTERFACE C A N BE MORE A C C U R A T E L Y ASSESSED WHEN

C O M P U T I N G A L U M I N U M A C T I V I T I E S .

C. EXPER I MENTAL PROCEDURE :

THE ASSEMBLED REACTION TUBE (IRON OR ALUMINA) WAS INSERTED

V E R T I C A L L Y I N A M U L L I T E TUBE, AND A LONG QUARTZ TUBE, C L O S E D AT T H E BOTTOM,

+ WAS P L A C E D E I T H E R I N S I D E T H E I/4" D I A . I N N E R T U B E Of T H E I R O N T U B E OR J

ALONG THE OUTSIDE OF THE ALUMINA TUBE. THE Q U A R T Z TUBE ACCOMMODATED A

-8-

P L A T I NUM-PLAT I NUM-IG$ RHODI UM THERMOCOUPLE WH I CH COULD BE R A I SED OR LOWERED

ALONG THE LENGTH OF T H E R E A C T I O N TUBE FROM O U T S I D E THE MULLITE TUBE. THE

MULLITE TUBE WAS CLOSED WITH A WATER-COOLED BRASS HEAD, USING AN APIESON

W A X AS A SEALANT. THE BRASS HEAD HAD AN OPENING FOR THE Q U A R T Z THERMO-

COUPLE P R O T E C T I O N T U B E AND A METAL-TO-GLASS C O N N E C T I O N T O A VACUUM S Y S T E M

C O N S I S T I N G O F A TWO-STAGE M E C H A N I C A L PUMP, A THREE-STAGE O I L D I F F U S I O N

PUMP, A COLD T R A P AND A M c L f o D GAUGE. THE MULLITE TUBE WAS CONTINUOUSLY

E V A C U A T E D DURING THE RUN T O A PRESSURE. OF BETTER THAN 2 MICRONS (HG) .

THE MULLITE TUBE WAS P O S I T I O N E D BETWEEN TWO SEPARATE R E S I S T A N C E -

WOUND TUBE FURNACES. THE BOTTOM FURNACE USED NICHROME V R E S I S T A N C E WIRE

AND THE TOP F U R N A C E ( A L W A Y S A T A HIGHER T E M P E R A T U R E T H A N THE BOTTOM) HAD

A SUPER-KANTHAL WINDING. EACH FURNACE W A S CONTROLLED B Y A SEPARATE SINGLE-

POINT C E L E C T R A Y C O N T R O L L E R T O W I T H I N - I'C. +

B Y S U I T A B L E FURNACE S E T T I N G S , D I F F E R E N T TEMPERATURE G R A D I E N T S

WERE IMPOSED ON THE R E A C T I O N TUBES I N THE TEMPERATURE RANGE 750-1150"c.

THE AL SURFACE OR THE AL-NACL I N T E R F A C E WAS ALWAYS KEPT AT THE TEMPERATURE

MINIMUM AND A T O T A L T E M P E R A T U R E G R A D I E N T OF A P P R O X I M A T E L Y 150" TO 2 5 0 O c

ALONG T H E E N T I R E L E N G T H OF T H E R E A C T I O N T U B E WAS G E N E R A L L Y USED. O N H E A T -

I N G T H E A L U M I N A TUBES, T H E A L U M I N U M M E L T E D AND S E A L E D T H E I N T E R I O R OF

THE TUBE FROM THE REST OF THE SYSTEM (SEE FIGURE 5).

ACCURATE TEMPERATURE MEASUREMENTS WERE MANDATORY, S I N C E A TEMPER-

ATURE ERROR O F I "c. WOULD L E A D T O AN ERROR I N T H E C A L C U L A T E D A L U M I N U M

A C T I V I T Y OF I T O 5%. THE THERMOCOUPLES WERE CALIBRATED T O AN A C C U R A C Y

+ O F - 1/2" U S I N G T H E F R E E Z I N G P O I N T S O F Z I N C , A N T I M O N Y AND COPPER AND

FOLLOWING A PROCEDURE DESCRIBED B Y THE NATIONAL BUREAU OF STANDARDS (20) - w THE TEMPERATURE GRADIENT WAS DETERMINED B Y MEASURING THE T E M P E R A T U R E E V E R Y 0

-9-

c *

CENTIMETER ALONG THE OUTSIDE OF THE R E A C T I O N TUBE. SINCE THE POSIT IONS

OF THE S P E C I M E N S WERE KNOWN, T H E I R TEMPERATURES COULD B E D E T E R M I N E D . T O

I M P R O V E T H E ACCURACY OF T H E TEMPERATURE MEASUREMENTS IN A L U M I N A T U B E S

C A L I B R A T I O N RUNS WERE MADE UNDER O T H E R W I S E I D E N T I C A L C O N D I T I O N S U S I N G

A L U M I N A T U B E I N W H I C H T H E T O P WAS P I E R C E D AND T H E TEMPERATURE G R A D I E N T

COULD B E MEASURED B O T H I N S I D E AND O U T S I D E T H E R E A C T I O N T U B E . B Y CARE-

F U L L Y D U P L I C A T I N G T H E TEMPERATURE G R A D I E N T OF T H E E X P E R I M E N T A L RUNS T H E

A C T U A L TEMPERATURE OF T H E S P E C I M E N S COULD B E D E T E R M I N E D Q U I T E S A T I S F A C -

T O R I L Y

THE LENGTH OF A RUN W A S G E N E R A L L Y ABOUT T H I R T Y DAYS, ALTHOUGH

SOMEWHAT LONGER P E R I O D S WERE USED FOR LOWER TEMPERATURE RUNS. RUNS MADE

W I T H I R O N T U B E S WERE T E R M I N A T E D B Y WATER Q U E N C H I N G I N ORDER T O PRESERVE

THE COMPOSITIONS OF THE SPECIMENS AT THE RUN T E M P E R A T U R E . RUNS MADE

W I T H A L U M I N A T U B E S WERE T E R M I N A T E D B Y A I R - C O O L I N G T H E E V A C U A T E D M U L L I T E

TUBES; A P P R O X I M A T E L Y 15 MINUTES WERE R E Q U I R E D T O COOL T O T E M P E R A T U R E S AT

W H I C H D I F F U S I O N AND R E A C T I O N R A T E S WERE N E G L I G I B L E W I T H R E S P E C T T O S H I F T -

ING THE: E Q U I L I B R I U M COMPOSITION OF THE SPECIMENS. THAT EQUILIBRIUM

C O M P O S I T I O N S WERE P R E S E R V E D WAS A S C E R T A I N E D B Y R E M O V I N G A SURFACE L A Y E R

FROM THE SPECIMENS PRIOR T O CHEMICAL A N A L Y S E S . THE ALUMINA SPECIMEN

T U B E S WERE U S U A L L Y D I S A S S E M B L E D B Y I N S E R T I N G T H E LOWER P A R T OF T H E T U B E

I N T O A SHORT R E S I S T A N C E FURNACE P R E H E A T E D T O A TEMPERATURE ABOVE T H E

MELTING POINT OF ALUMINUM AND B Y MELTING THE ALUMINUM. THE SPECIMENS

WERE H E A T E D O N L Y T O MODERATE T E M P E R A T U R E S S O T H A T NO E V A P O R A T I O N O F A L U -

M I N U M OR O X I D A T I O N O F T H E S P E C I M E N S OCCURRED. I N A FEW E X P E R I M E N T S THE

A L U M I N A T U B E S WERE CUT OPEN W I T H A D I A M O N D WHEEL B U T S P E C I M E N S W I T H A H I G H

A L U M I N U M CONTENT WERE SO B R I T T L E T H A T T H E Y WOULD T E N D T O B R E A K .

15

D. ANALYSIS OF SPECIMENS:

THE IRON CONTENT OF E A C H SPECIMEN WAS DETERMINED B Y A VOLUMETRIC

WAS T A K E N AS T H E D I F F E R E N C E O F T H E

THE E S T I M A T E D ERROR O F THE A N A L Y S I S WAS L E S S T H A N - 0.255 AL.

I N G T H E S P E C I M E N S A F T E R E Q U I L I B R A T I O N THE R E S U L T S O F THE V O L U M E T R I C A N A L -

Y S I S COULD B E CHECKED. HOWEVER, A CHECK 8 Y W E I G H I N G WAS NOT P O S S I B L E

I R O N CONTENT S U B T R A C T E D FROM loo$* +

BY W E I G H -

W I T H S P E C I M E N S CUT FROM T H E I R O N - A L U M I N U M S H E E T S I N C E I T S S T A R T I N G COMPO-

S I T I O N WAS NOT S U F F I C I E N T L Y CONSTANT.

1 1 1 . EVALUATION OF EXPERIMENTAL RESULTS

AFTER EQUILIBRATION AND A N A L Y S I S THE A C T I V I T Y OF ALUMINUM OF

T H E S P E C I M E N S WAS C A L C U L A T E D U S I N G THE TEMPERATURE O F T H E S P E C I M E N S AND

O F T H E A L U M I N U M SOURCE AND THE VAPOR PRESSURE OF PURE A L U M I N U M .

I N T H E ABSENCE O F S O D I U M C H L O R I D E T H E A C T I V I T Y O F A L U M I N U M IS

S I M P L Y G I V E N B Y T H E R A T I O OF T H E VAPOR PRESSURE OF A L U M I N U M OF T H E L I Q U I D

ALUMINUM SOURCE (SINCE I T I S HELD A T THE T E M P E R A T U R E M I N I M U M I N THE CLOSED

S Y S T E M I T S VAPOR PRESSURE IS A L S O E Q U A L T O T H E P A R T I A L P R E S S U R E S O F A L L

THE SPECIMENS A F T E R E Q U I L I B R A T I O N ) AND THE V A P O R PRESSURE OF PURE ALUMINUM

AT T H E TEMPERATURE OF T H E S P E C I M E N :

FROM A SERIES OF RUNS WITH DIFFERENT ALUMINUM SOURCE TEMPERATURES

I S O T H E R M A L A C T I V I T Y - C O M P O S I T I O N CURVES CAN B E O B T A I N E D .

- I I -

THE A C T I V I T Y C O E F F I C I E N T S OF A L U M I N U M qL AND OF I R O N GE, AND

Q HFE 9 AND E N T R O P I E S DSAL AND d3FE, A N D THE MOLAR Q U A N T I T I E S CAN B E

D E R I V E D U S I N G WELL KNOWN E Q U A T I O N S :

T H E P A R T I A L MOLAR FREE E N E R G I E S nFAL AND AZFE, ENTHALPIES d~~~ -

N =N FE FE

F E

ASM =

THE E V A L U A T I O N OF

T O A C C E L E R A T E T H E

AH^ - A G ~ T

A C T I V I T I E S IS D I F F E R E N T WHEN S O D I U M C H L O R I D E I S ADDED

E V A P O R A T I O N OF ALUMINUM. THE TRANSPORT OF ALUMINUM IN

THE G A S PHASE I S CAUSED B Y THE FORMATION OF ALUMINUM SUBCHLORIDE ALCL,

A PHENOMENON w H 1 c H HAS B E E N F t R s T OBSERVED B Y WI L L M O R E ( 2 1 1. THE REACT 1 oNs

I M P L I C I T I N T H E F O R M A T I O N OF A L U M I N U M S U B H A L I D E S H A V E B E E N I N V E S T I G A T E D

QUITE EXTENSIVELY, E S P E C I A L L Y B Y GROSS (22) WHO S T U D I E D THE C O M M E R C I A L

A P P L I C A T I O N OF T H E R E A C T I O N AND USED I T A L S O F O R E Q U I L I B R I U M MEASUREMENTS (18)

As O R I G I N A L L Y PROPOSED A L U M I N U M TRICHLORIDE ALCL WAS T O BE ADDED 3 T O THE S Y S T E M T O FORM ALCL A C C O R D I N G T O THE FOLLOWING R E A C T I O N :

3 ( G ) = 3ALCL(G) + ALCL (9)

EXPERIMENTAL D I F F I C U L T I E S ( E . G . THE E X T R E M E HYGROSCOPIC N A T U R E O F ALCL ) 3

MADE I T N E C E S S A R Y T O ADOPT T H E R E A C T I O N BETWEEN A L U M I N U M AND S O D I U M

C H L O R I D E FOR T H I S I N V E S T I G A T I O N :

FROM E X I S T I N G THERMODYNAM.IC D A T A (23) THE F O L L O W I N G E Q U A T I O N FOR T H E CHANGE

I N F R E E ENERGY O F R E A C T I O N 10 WAS C O M P I L E D :

BETWEEN 1074" AND 2000°K T H I S EQUATION C A N A L S O BE REPRESENTED IN A MORE

S I M P L I F I E D FORM W I T H O U T ANY L O S S I N ACCURACY:

AGO,- = 98,200 - 51 .OT (12)

BELOW 1074°K S O D I U M CHLORIDE I S SOLID AND WE H A V E T O ADD THE E Q U A T I O N

T O E Q U A T I O N I O . THE CHANGE I N FREE E N E R G Y FOR R E A C T I O N 13 ACCORDING T O

K U 6 A S C H E W S K l (23) I s :

OR SIMPLIFIED: AGO.,- = 6,660-6.2~

AND THE CHANGE I N FREE E N E R G Y FOR THE R E A C T I O N 1 6

(4 + NACL = ALCL + NA A L ( L ) (SI (4

I S AGOT = 104,860 - 57.2T.

B Y APPL I C A T I ON OF THE GI BBS-HELMHOLTZ EQUAT I ON A H " O F R E A C T I ON

I O C A N BE EQUATED WITH 98,200 CAL AND THAT OF R E A C T I O N 16 WITH 104,860

C A L I N T H E T E M P E R A T U Z E RANGE OF OUR E X P E R I M E N T S .

-I 3-

I N OUR E X P E R I M E N T A L ARRANGEMENT T H E L I Q U I D A L U M I N U M WAS E I T H E R

COVERED W I T H A T H I N L A Y E R O F L I Q U I D OR S O L I D S O D I U M C H L O R I D E OR T H E S O D I U M

C H L O R I D E WAS K E P T I N A S E P A R A T E A L U M I N A C R U C I B L E W I T H I N T H E S P E C I M E N T U B E

- AT T H E SAME TEMPERATURE AS T H E ALUMINUM. I T H A S B E E N FOUND T H A T WHENEVER

S O D I U M C H L O R I D E WAS L I Q U I D I T COULD NOT B E K E P T I N T H E S P E C I M E N T U B E FOR

MORE THAN A FEW D A Y S . SINCE JUST BELOW THE MELTING POINT SODIUM CHLORIDE

COULD B E R E T A I N E D FOR MORE T H A N A MONTH,THE REASON FOR T H E LOSS OF LIQUID

S A L T IS MOST P R O B A B L Y D U E T O T H E D I F F E R E N C E I N SURFACE T E N S I O N BETWEEN

SODIUM CHLORIDE AND ALUMINUM. LIQUID SODIUM CHLORIDE WETS THE ALUMINA

SURFACE MUCH B E T T E R T H A N A L U M I N U M (WE OBSERVED O N L Y AT T H E VERY H I G H E S T

T E M P E R A T U R E S A W E T T I N G OF A L U M I N A B Y AL) AND W I L L CREEP OUT OF T H E S P E C I -

MEN T U B E A S A T H I N F I L M BETWEEN T H E A L U M I N A W A L L AND T H E M O L T E N ALUMINUM.

E Q U ~ L I B R A T I O N I N RUNS WITH S O D I U M CHLORIDE WAS THEREFORE ASSURED ONLY AT

T E M P E R A T U R E S BELOW T H E M E L T I N G P O I N T OF T H E S A L T .

THE E V A L U A T I O N OF RUNS WITH SODIUM CHLORIDE I S BASED ON THE

F O L L O W I N G P R I N C I P L E :

THE G A S MIXTURE I N THE SPECIMEN TUBE CONTAINS C E R T A I N AMOUNTS

O F GASEOUS NACL, AL, ALCL, AND NA A C C O R D I N G T O T H E E Q U I L I B R I U M BETWEEN

THESE SPECIES I N THE G A S PHASE. D IRECTLY ABOVE THE SURFACE OF AL-NACL,

AL T H E P A R T I A L PRESSURE O F A L U M I N U M P W I L L E Q U A L T H A T O F T H E VAPOR PRESSURE

W I L L B E D E T E R M I N E D B Y T H E E Q U I - PAL OF PURE ALUMINUM. AT L A C H SPECIMEN

LIBRIUM BETWEEN THE GASEOUS SPECIES A T THE P A R T I C U L A R TEMPERATURE. THE

S P E C I M E N S WILL R E A C T W I T H T H E A L U M I N U M VAPOR U N T I L T H E A C T I V I T Y O F A L U M I N U M

I S THE SAME I N THE A L L O Y PHASE AND I N THE G A S PHASE. THE A C T I V I T Y WILL

BE A FUNCTION BOTH OF THE TEMPERATURE OF THE AL-NACL INTERFACE AND OF THE

TEMPERATURE OF T H E S P E C I M E N .

- I 4-

THE L O C A L P 4 R T I A L PRESSURE OF ALUMINUM, I .E. 'AL N E A R T H E

S P E C I M E N , I S O B T A I N E D B Y T H E F O L L O W I N G C A L C U L A T I O N S :

(4 (4 (4 (9) AH' I (19 ) AL + NACL = ALCL + NA

THE E Q U I L I B R I U M CONSTANT OF T H I S R E A C T I O N IS: 1

AND FROM T H E CHANGE I N T H E STANDARD F R E E ENERGY

A G O = -26,690 - I4.68T LOG T + 53.51T (21 1

WE CAN SEE T H A T W I T H I N C R E A S I N G TEMPERATURE THE R E A C T I O N WILL S H I F T

ONLY VERY S L I G H T L Y T O T H E L E F T .

FROM E Q U A T I O N 20 WE O B T A I N T H E P A R T I A L PRESSURE OF A L U M I N U M

AT T = T I , THE P A R T I A L PRESSURE OF AL I S EQUAL TO THE P A R T I A L

PRESSURE OF AL O V E R PURE AL (WHERE TI I S THE R E S E R V O I R TEMPERATURE AND T - I S THE SPEC I MEN TEMPERATURE) .

S I N C E T H E P A R T I A L PRESSURE O F A L U M I N U M I S S E V E R A L ORDERS O F

M A G N I T U D E L E S S T H A N T H A T O F T H E OTHER REACTANTS, I T S C O N T R I B U T I O N TO T H E

T O T A L PRESSURE MAY B E N E G L E C T E D AND T H E T O T A L PRESSURE O F T H E R E A C T A N T S

(4 THROUGHOUT THE TUBE SET EQUAL TO P = pNAcL + pALcL + p N A *

AND NA

SINCE ALCL

- - ALCL - - 'NA ARE FORMED I N EQUAL S T O I C H I O M E T R I C PROPORTIONS, p (4 CONSTANT S I N C E A S L I G H T S H I F T O F K' W I T H TEMPERATURE WILL NOT A F F E C T

(T 1 AND PNA DUE TO THE SMALLNESS OF pAL. THE PARTIAL PRESSURE OF SODIUM

'ALcL

L

L -

C H L O R I D E CAN VARY BETWEEN W I D E L I M I T S W I T H O U T A F F E C T I N G T H E C A L C U L A T I O N S

A S LONG AS PNACL I S MUCH LARGER THAN p A L J \ . E . THE NACL RESERVOIR COULD

B E K E P T AT SOME LOWER TEMPERATURE (E.G. RUN I-K).

TAKING & " I A S V I R T U A L L Y I N D E P E N D E N T OF T , VAN'T HOFF'S EQUATION

CAN BE A P P L I E D . B Y D I V I D I N G E Q U A T I O N 22 BY EQUATION 23 AND NOTING T H A T

T H E P A R T I A L P R E S S U R E S O F T H E COMPONENTS, OTHER T H A N T H A T OF ALUMINUM,

ARE V I R T U A L L Y CONSTANT W I T H I N T H E TUBE, THE F O L L O W I N G E Q U A T I O N IS O B T A I N E D :

THE L O C A L A C T I V I T Y OF ALUMINUM OF A SPECIMEN IS:

To O B T A I N BAL FROM E Q U A T I O N 24 WE H A V E T O EXPRESS T H E P A R T I A L PRESSURE

- OF AL O V E R PURE L I Q U I D AL A S A FUNCTION OF TEMPERATURE:

C O M B I N I N G E Q U A T I O N S 24 A N D 26 WE G E T :

PH" I = E X P - 1 - +)A : E X P -i"'.v;p* AL -+y [ + A H o ~ ~ ~ ~ . A L (9, - +)]

R a = E X P - A L (TI

SODIUM CHLORIDE ( I .E., 98,200 C A L / M O L E ) , THE SUM OF THE ENTHALPY CHANGES

31 899 4. .A- -16-

I N EQUATION 27 MUST BE COMBINED WITH THE E N T H A L P Y CHANGE OF E V A P O R A T I O N

OF SODIUM C H L O R I D E # S I N C E THE HEAT C A P A C I T I E S OF L I Q U I D AND GASEOUS NACL

ARE KNOWN ( 2 3 ) , THE FOLLOWING R E L A T I ON I s V A L ID FOR AL-NACL R ~ S E R V O I R

TEMPERATURES FROM 801-9oo"c. ( I .E., THE HEAT OF E V A P O R A T I O N OF NACL WAS

C A L C U L A T E D FOR T H I S TEMPERATURE RANGE AND FOUND T O H A V E A N E A R L Y CONSTANT

V A L U E OF 42,950 C A L O R I E S ) :

= 55,250 C A L O R I E S (28) A H o ~ ~ ~ ~ . NACL = aH0 - A H " ' + A H o ~ ~ ~ ~ . AL

FOR EXPERIMENTS WITH SOLID SODIUM CHLORIDE A COMBINATION OF

H" OF REACTION 1 6 ( I .E. 104, 860 CALORIES) WITH A H " OF SUBLIMATION OF

SODIUM CHLORIDE WILL G I V E THE SAME V A L U E . THUS FOR ALL RUNS WITH SODIUM

C H L O R I D E I N T H E CONDENSED S T A T E T H E F O L L O W I N G E Q U A T I O N I S A P P L I C A B L E FOR

C A L C U L A T I N G T H E A C T I V I T Y O F A L U M I N U M I N T H E S P E C I M E N S :

I I = -12,080 ( - - ) T I

WHERE TI I S T H E R E S E R V O I R TEMPERATURE AND T THE S P E C I M E N T E M P E R A T U R E .

I V . EXPERIMENTAL RESULTS

FROM A C U R S O R Y G L A N C E AT THE IRON-ALUMINUM PHASE DIAGRAM (FIG. I )

ONE CAN E X P E C T T H A T T H E A C T I V I T Y OF A L U M I N U M WILL SHOW A R A T H E R PRONOUNCED

N E G A T I V E D E V I A T I O N FROM R A O U L T ' S L A W I N THE REGION OF SOLID SOLUTIONS OF

A L U M I N U M I N I R O N AND T H A T T H E A C T I V I T Y WILL I N C R E A S E M A R K E D L Y AT ONE OR

MORE O F T H E I N T E R M E T A L L I C COMPOUNDS T O APPROACH I D E A L I T Y A S T H E C O M P O S I T I O N

APPROACHES T H A T O F PURE A L U M I N U M .

- I 7-

IRON REACTION TUBES:

W I T H T H E M A T H E M A T I C A L R E L A T I O N S H I P S P R E V I O U S L Y D E R I V E D T H E

A C T I V I T Y O F A L U M I N U M WAS C A L C U L A T E D U S I N G E I T H E R E Q U A T I O N I OR E Q U A T I O N

29. THE E Q U A T I O N FOR T H E VAPOR PRESSURE O F A L U M I N U M AS A F U N C T I O N OF

TEMPERATURE WAS T A K E N FROM KUBASCHEWSKI (23) . THIS VALUE HAS BEEN ACCEPTED

I N A L L RECENT C O M P I L A T I O N S (24’25’26). THE RESULTS FOR TWO RUNS ARE

L ISTED I N TABLE I AND 2 AND PLOTTED I N FIG. 6. WAS USED A S AN ACCELERATOR, I N RUN 3 (TABLE 2 ) PURE ALUMINUM WAS E V A P O R -

ATED. COLUMN 3 (TABLE 2 ) G I V E S THE V A P O R PRESSURE OF PURE ALUMINUM A T

E A C H SPECIMEN TEMPERATURE. I T SHOULD BE EMPHASIZED THAT FIG. 6 I S NOT

I N RUN I (TABLE I ) NACL

AN I S O T H E R M A L A C T I V I T Y - C O M P O S I T I O N P L O T .

I T C A N BE SEEN FROM FIG. 6 THAT THE QUALITATIVE E X P E C T A T I O N

OF A STRONG NEGATIVE DEVIAT ION FROM R A O U L T ’ S L A W I S NOT BORNE OUT.

ALTHOUGH THE D A T A SHOW NO SYSTEMATIC DEVIAT ION W I T H RESPECT T O THE I N I T I A L

A L U M I N U M CONTENT OF T H E S P E C I M E N S T H E R E S U L T S MUST B E I N S E R I O U S ERROR.

T O A C H I E V E E Q U I L I B R A T I O N O F I R O N S P E C I M E N S I N I R O N T U B E S T H E D I F F U S I O N

OF A L U M I N U M I N I R O N H A S T O B E T H E R A T E D E T E R M I N I N G S T E P A S COMPARED W I T H

T H E R A T E O F MASS T R A N S F E R O F A L U M I N U M FROM T H E R E S E R V O I R T O T H E S P E C I M E N S .

THE INSIDE WALL OF THE SPECIMEN TUBE WOULD THEN ALSO BECOME EQUILIBRATED

W I T H R E S P E C T T O A L U M I N U M AND WHATEVER A L U M I N U M WOULD D I F F U S E I N T O T H E

W A L L WOULD NOT A F F E C T T H E P A R T I A L PRESSURE O F A L U M I N U M W I T H T H E C L O S E D

TUBE. UNDER THESE CONDITIONS I T SHOULD BE POSSIBLE T O APPROACH EQUILIBRIUM

I N T H E T H I N S P E C I M E N S . V A R l A T l O N S O F T I M E AND TEMPERATURE AND A D D I T I O N

O F NACL D I D NOT IMPROVE T H E R E S U L T S SO T H A T E X P E R I M E N T S I N I R O N TUBES

WERE F I N A L L Y D I S C O N T I N U E D AND A L L T H E D A T A H A D T O B E D I S C A R D E D . I T WAS

CONCLUDED T H A T UNDER A L L E X P E R I M E N T A L C O N D I T I O N S T H E R A T E O F E V A P O R A T I O N

-18-

O F ALUMINUM AND NOT T H E D I F F U S I O N I N T O I R O N WAS T H E RATE D E T E R M I N I N G S T E P

AND EQUILIBRATION COULD NOT BE A C H I E V E D I N IRON TUBES. FURTHER EVIDENCE

I S PROVIDED B Y THE FACT THAT IN RUN 3 THE 5 MIL IRON AND IO MIL IRON - 16% ALUMINUM SPECIMENS L I E ON A SMOOTH C U R V E . I F DIFFUSION HAD CONTROLLED

T H E R E A C T I O N THE TWO T Y P E S OF S P E C I M E N S SHOULD L I E ON SEPARATE CURVES.

ALUMINA REACT I ON TUBES:

THE R E S U L T S O B T A I N E D FROM S U C C E S S F U L RUNS I N A L U M I N A R E A C T I O N

TUBES ARE L ISTED IN TABLES I I I T O VI I I AND I N FIG. 7 AND 8 AS NONISOTHERMAL

A C T I V I T Y - C O M P O S I T I O N P L O T S W I T H T H E NUMBER I N D I C A T I N G THE S P E C I M E N TEMPER-

ATURE. RUN I - K WAS MADE I N AN EXCEPTIONALLY LONG (24") A L U M I N A TUBE, AND

I T WAS NOT P O S S I B L E T O K E E P THE VERY TOP O F T H E T U B E AT A H I G H E R TEMPERA-

TURE T H A N THE AL-NACL R E S E R V O I R AT THE BOTTOM. AS A RESULT, S O L I R S O D I U M

CHLORIDE AND DROPLETS OF ALUMINUM (1/8" D I A . M A X . ) CONDENSED AT THE TOP

OF THE ALUMINA TUBE. THUS, THE ALUMINUM-SODIUM CHLORIDE SOURCE T E M P E R A -

TURE FOR T H E UPPERMOST S P E C I M E N S WAS THAT OF THE TOP OF T H E TUBE, W H I L E

THE C O R R E S P O N D I N G TEMPERATURE FOR T H E LOWER S P E C I M E N S WAS T H A T O F T H E

SURFACE OF THE A L U M I N U M AT THE BOTTOM OF T H E T U B E . ALTHOUGH A L L THE NACL

I N THE T U B E CONDENSED AT T H E 'TOP, THE P A R T I A L PRESSURE O F NACL WAS KNOWN

TO B E NOT C R t T l C A L AS FAR AS A F F E C T I N G T H E C A L C U L A T E D A C T I V I T Y OF A L U M I N U M

AS A F U N C T I O N OF R E S E R V O I R AND SPE:ClMEN TEMPERATURE. I N V I E W O F THE UN-

CERTAINTIES INVOLVED,DATA OF RUN I - K H A V E NOT BEEN INCLUDED I N FIG. 7 AND

WERE G I V E N NO WEIGHT IN T H E F I N A L E V A L U A T I O N . HOWEVER, FROM TABLE 1 1 1

I T CAN B E SEEN T H A T A C T I V I T I E S FOR THE UPPERMOST AND T H E LOWEST S P E C I M E N S

C A L C U L A T E D AS O U T L I N E D ABOVE AGREE VERY WELL W I T H THE R E S U L T S FROM OTHER

RUNS. A C T I V I T Y V A L U E S FOR SPECIMENS I N THE MIDDLE OF THE TUBE ARE AMBIG-

UOUS SINCE NO DEFINITE AL-SOURCE TEMPERATURE C A N BE ASSIGNED T O THEM.

- 19 -

FOR RUN I - N BOTH IRON AND IRON - 16% ALUMINUM SPECIMENS WERE

USED IN ALTERNATE POSITIONS AND T H E I R A C T I V I T I E S I N FIG. 7 FALL ON A

SMOOTH C U R V E ( FE-l 6$ AL SPEC I MENS H A V E THE TEMPERATURE UNDERL I NED) .

ALTHOUGH T H I S B Y I T S E L F I S NOT ENOUGH T O BE I N D I C A T I V E OF COMPLETE EQUI-

L IBRATION THE RESULTS AGREE V E R Y WELL W I T H THOSE OF OTHER RUNS. DIFFERENT

S P E C I M E N T H I C K N E S S AND S T A R T I N G C O M P O S I T I O N HAS THEREFORE NO I N F L U E N C E

ON T H E F I N A L R E S U L T S .

ALL THE OTHER RUNS SHOW V E R Y L I T T L E SCATTER (WITH THE POSSIBLE

EXCEPTION O F RUN I-S) AND COULD BE PLOTTED ON SMOOTH C U R V E S I N FIG. 7.

AT HIGHER ALUMINUM CONTENTS THE D A T A SHOW QUITE AN I N C R E A S E I N S C A T T E R

AS SEEN I N FIG. 8. THESE SPECIMENS WERE V E R Y C L O S E TO THE ALUMINUM

SOURCE, I N C R E A S E D A P P R E C I A B L Y I N T H I C K N E S S D U R I N G THE E X P E R I M E N T AND AS

A C O N S E Q U E N C E WARPED QUITE C O N S I D E R A B L Y . ALL THESE FACTORS MADE A C C U R A T E

MEASUREMENTS D I F F I C U L T * THE D A T A HAVE THEREFORE B E E N P L O T T E D AS SHOWN

I N FIG. 8 AND NO FURTHER ATTEMPT H A S BEEN MADE T O C O R R E C T THE RESULTS

FOR DIFFERENCES IN TEMPERATURE. THE A V E R A G E C U R V E DRAWN THROUGH THE

P O I N T S SHOULD N E V E R T H E L E S S G I V E A GOOD A P P R O X I M A T I O N OF T H E A C T I V I T Y OF

ALUMINUM I N THESE A L L O Y S AT ABOUT 1200°K.

I S O T H E R M A L A C T I V I T Y - C O M P O S I T I O N P L O T S CAN B E O B T A I N E D FROM

FIG. 7 B Y E I T H E R S E L E C T I N G I S O T H E R M A L S P E C I M E N S FROM THE CURVES OR L O C A T -

I N G THESE P O I N T S B Y I N T E R P O L A T I O N AND D R A W I N G THE A C T I V I T Y - C O M P O S I T I O N

C U R V E FOR THE SELECTED TEMPERATURE. WHEN D A T A ARE NOT NUMEROUS I T I S

P R E F E R A B L E TO C A L C U L A T E P A R T I A L MOLAR E N T H A L P Y V A L U E S AT C E R T A I N C O M P O S I -

TIONS BY SELECTING THE MOST A C C U R A T E C U R V E (RUN I - P I N FIG. 7) AS THE

REFERENCE C U R V E AND APPLYING V A N ' T HOFF'S E Q U A T I O N ( E Q U A T I O N 5) TO THE

D I F F E R E N C E I N A C T I V I T Y BETWEEN T H E REFERENCE CURVE AND THE OTHER CURVES.

-20-

SINCE THE V A L U E S C A N BE TAKEN A S CONSTANT FOR A LIMITED RANGE OF

TEMPERATURE T H E R E S U L T S T H U S O B T A I N E D CAN B E AVERAGED AND T H E S E AVERAGE

V A L U E S USED IN E Q U A T I O N 5 T O C A L C U L A T E A C T I V I T I E S AT OTHER TEMPERATURES,

A G A I N R E L A T I V E T O THE A C T I V I T I E S OF THE REFERENCE CURVE. RESULTS OF

THESE CALCULATIONS ARE SHOWN I N TABLE I X . THE A V E R A G E VALUES I N COLUMN

6 WITH LIQUID ALUMINUM AS STANDARD S T A T E ARE THE ARITHMETIC MEAN OF RUNS

I-N, 1-0, AND I - R . RUN I -S WAS NOT INCLUDED S I N C E THE D A T A SHOW MORE

S C A T T E R AND NACL WAS USED A S A C C E L E R A T O R . THE AGREEMENT, HOWEVER, WITH

R E S U L T S FROM OTHER RUNS I S GOOD ENOUGH T O CONCLUDE T H A T R E L I A B L E V A L U E S

C A N BE OBTAINED USING NACL. THE D A T A I N COLUMN 7 ARE THOSE GIVEN B Y

HULTGREN AND COWORKERS (27) I N FORM OF T H E E Q U A T I O N

(30) AtAL = (-66,000 + 56,000 NFE) NFE 2

THESE RESULTS ARE V A L I D A T 298°K AND FOR SOLID ALUMINUM A S

THE STANDARD STATE. SINCE

AT 1200'K (2,000 CAL/G-ATOM) F(AL 1

= 2;06~ - I .48 x

T H E H E A T OF F U S I O N O F A L U M I N U M H

C A L C U L A T E D FROM E Q U A T I O N

(32) + I ,870

WAS SUBTRACTED T O G I V E THE VALUES I N COLUMN 8 NOW REFERRING T O LIQUID

A L U M I N U M A S T H E STANDARD S T A T E .

I S O T H E R M A L A L U M I N U M A C T I V I T Y - C O M P O S I T I O N CURVES FOR 1200',

1300" AND 1h00"K D E R I V E D FROM THE A V E R A G E APAL D A T A I N TABLE t x ARE

SHOWN I N FIG. 9. THE CORRESPONDING PLOT FOR THE A C T I V I T Y COEFFICIENT I S

SHOWN I N FIG. I O . THE CURVES HAVE BEEN EXTRAPOLATED T O ZERO CONCENTRATION

P A R T L Y B Y A P P R O X I M A T I O N , P A R T L Y B Y F O L L O W I N G T H E CURVATURE SUGGESTED B Y

-21-

GROSS' D A T A ( ' 7 ) . THE ACCURACY OF T H E D A T A BELOW 30 A T O M l C % AL IS T H E R E -

FORE NOT V E R Y HIGH. W I T H THE E X T R A P O L A T E D A C T I V I T Y C O E F F I C I E N T S AHAL V A L U E S H A V E B E E N E S T I M A T E D FOR T H I S C O N C E N T R A T I O N RANGE AND L I S T E D I N

TABLE I X (COLUMN 6 ) .

PARAMETERS H A V E BEEN C A L C U L A T E D FOR IRON-ALUMINUM A L L O Y S FROM o T O 50

ATOMIC $ AL AT 1200°K ( T A B L E x ) .

BEEN PLOTTED I N FIG. I I AND E N T R O P Y V A L U E S I N F I G . 12. THESE PLOTS ARE

V A L I D FOR A TEMPERATURE O F 1200°K AND R E F E R T O S O L I D A L U M I N U M A S T H E

MAKING USE OF EQUAT I ON 2 T O 8, VARI ous THERMODYNAMI c

ENTHALPY AND FREE ENERGY VALUES H A V E

S T A N D A R D S T A T E . T O O B T A I N E N T R O P I E S FOR S O L I D A L U M I N U M A S T H E STANDARD

S T A T E A S I M I L A R C O R R E C T I O N H A S B E E N A P P L I E D AS FOR E N T H A L P Y V A L U E S

( E Q U A T I O N 31). THE E N T R O P Y CHANGE ON FUSION WAS C A L C U L A T E D FROM

as^(^) = 4.75 LOG T - 2.96 x IOm3T - 8.67 (33)

V. ERRORS

THE R E L I A B I L I T Y AND A C C U R A C Y OF THE RESULTS I S AFFECTED B Y

ERRORS I N H E R E N T I N THE METHOD OR I N THE MEASUREMENTS PERFORMED. I T IS

ASSUMED T H A T T H E F O L L O W I N G F A C T O R S ARE P O S S I B L E SOURCES O F ERRORS AND

M I G H T INTRODUCE AN E L E M E N T O F U N C E R T A I N T Y :

( A ) TEMPERATURE MEASUREMENT

( E ) P O S I T I O N O F S P E C I M E N S

(C) A N A L Y S I S OF S P E C I M E N S

( 0 ) I NCOMPLETE E Q U I L I B R A T I ON

( E ) THERMODYNAMl C D A T A

( F ) S I D E R E A C T I O N S

( G ) T H E R M A L D I F F U S I ON

I N T H E SUBSEQUENT PARAGRAPHS T H E I N F L U E N C E AND M A G N I T U D E O F ERRORS DUE

T O T H E S E F A C T O R S 1 S D I SCUSSED.

-22-

831 27

THE A C C U R A C Y OF THE T E M P E R A T U R E MEASUREMENTS I S AFFECTED B Y

THE PERFORMANCE OF THE CONTROLLERS AND THE THERMOCOUPLES. BOTH CONTROLLERS

+ WERE O P E R A T I N G W I T H I N - I O C AND THE TEMPERATURE GRAD1 ENT, ONCE A S T E A D Y

S T A T E WAS REACHED, D I D NOT CHANGE MORE T H A N I T O 2°C OVER T H E P E R I O D O F

+ A RUN ( I MONTH) . THE THERMOCOUPLES WERE CALIBRATED T O WITHIN - O . 5 " C .

4- THE POSIT ION OF THE SPECIMENS WAS MEASURED T O W I T H I N - 0.5 MM

+ WHICH I S EQUIVALENT T O AN UNCERTAINTY OF - 0 . 5 " ~ I N THE STEEPEST PART OF

T H E TEMPERATURE G R A D I E N T B U T T H I S U N C E R T A I N T Y WAS I N C R E A S E D D U R I N G THE

TEMPERATURE MEASUREMENTS DUE T O T H E D I F F E R E N C E I N T H E R M A L E X P A N S I O N O F

THE COMPONENT P A R T S OF THE SYSTEM. AN A C C U R A T E ESTIMATE OF T H I S ERROR

WAS NOT P O S S I B L E B U T I T S M A G N I T U D E I S MOST P R O B A B L Y NOT G R E A T E R T H A N

T H A T DUE T O THC TEMPERATURE MEASUREMENTS.

+ THE E R R O R I N THE A N A L Y S E S OF THE SPECIMENS WAS ABOUT - 0.25%.

THE IMPURITY L E V E L I N THE M A T E R I A L S USED WAS LOW ENOUGH so A S NOT T O

A F F E C T T H E R E S U L T S . A P O S S I B L E CHANGE I N T H E SURFACE C O N C E N T R A T I O N O F

T H E S P E C I M E N S D U R I N G Q U E N C H I N G WAS E L I M I N A T E D BY R E M O V I N G A T H I N SURFACE

L A Y E R P R I O R TO T H E A N A L Y S E S .

S I N C E I T C A N B E ASSUMED T H A T T H E ERRORS W I L L T O A N E X T E N T

C A N C E L E A C H OTHER OUT I T I S E S T I M A T E D T H A T T H E E F F E C T S D I S C U S S E D ABOVE

W I L L I N T R O D U C E A C O M B I N E D U N C E R T A I N T Y E Q U I V A L E N T T O -I 2°C O F T H E S P E C I M E N +

TEMPERATURE. SINCE A SMOOTH C U R V E WAS DRAWN THROUGH THE P O I N T S OF BOTH

T H E T E M P E R A T U R E G R A D I E N T AND T H E A C T I V I T Y - C O M P O S I T I O N P L O T T H E A S S U M P T I O N

OF A PARTIAL CONCELLATION OF ERRORS SEEMS T O BE JUSTIFIED. AN ERROR OF

+ - 2'c WILL H A V E D I F F E R E N T E F F E C T S ON T H E A C T I V I T Y V A L U E S D E P E N D I N G ON T H E

ALUMINUM CONTENT OF THE SPECIMENS.

BE A C C U R A T E T O - 2.5% AND THE MAGNITUDE OF THE ERROR WI L L I N C R E A S E T O

CLOSE T O - IC$ FOR SPECIMENS CONTAINING 75 ATOMIC $ A L .

AT 35 ATOMIC % AL THE A C T I V I T I E S WILL

+

+

-2 3-

THE COMPLETION OF E Q U I L I B R A T I O N WAS A S C E R T A I N E D B Y V A R Y I N G THE

LENGTH OF A RUN. AFTER ONE MONTH THE C O M P O S I T I O N OF THE S P E C I M E N S RE-

M A I N E D CONSTANT E V E N FOR T H E RUNS AT T H E LOWEST TEMPERATURE. N O E R R A T I C

D I F F E R E N C E S I N C O M P O S I T I O N BETWEEN RUNS AT T H E LOWEST AND H I G H E S T TEMPER-

ATURE W H I C H WOULD I N D I C A T E I N C O M P L E T E E Q U I L I B R A T I O N COULD BE OBSERVED AS

C A N BE SEEN FROM THE CALCULATED A i A L V A L U E S (TABLE I X ) . FURTHERMORE,

V A L U E S O B T A I N E D FROM S P E C I M E N S O F D I F F E R E N T T H I C K N E S S D I D NOT SHOW ANY

S Y S T E M A T I C D E V I A T I O N S .

ALL THE C A L C U L A T I O N S ARE BASED ON THERMODYNAMIC D A T A T A K E N FROM

L I T E R A T U R E AND ARE THEREFORE S U B J E C T T O R E V I S I O N WHENEVER MORE ACCURATE

D A T A WILL BECOME A V A I L A B L E . THE EXPERIMENTS WITH ALUMINUM ARE BASED ON

T H E VAPOR PRESSURE OF A L U M I N U M AND THOSE W I T H S O D I U M C H L O R I D E AND A L U M I N U M

DEPEND A L S O ON T H E E Q U I L I B R I U M CONSTANT OF THE R E A C T I O N BETWEEN T H E D I F -

FERENT S P E C I E S I N THE G A S PHASE. S INCE THE AGREEMENT BETWEEN RESULTS OB-

T A I N E D B Y B O T H METHODS I S VERY CLOSE,A S U B S T A N T I A L S H I F T I N T H E D A T A D U E

T O MORE ACCURATE THERMODYNAMIC E Q U A T I O N S I S NOT T O B E E X P E C T E D .

ACCORDING T O BREWER (28) A L U M I N U M I S C A P A B L E OF F O R M I N G TWO

GASEOUS SUBOXIDES, AL 0 AND ALO, AT E L E V A T E D T E M P E R A T U R E S . UNDER REDUC-

ING CONDIT IONS O N L Y AL 0 NEEDS TO BE CONSIDERED. ALTHOUGH I T I S U N C E R T A I N

I F I N THE TEMPERATURE RANGE OF OUR E X P E R I M E N T S EQUIL . IBRI~JM BETWEEN AL

2

2

(4 ’ A L ~ O ( ~ ) , AND AL 0 I S E S T A B L I S H E D , A KNOWLEDGE O F T H E P O S S I B L E E F F E C T

O F T H I S S I D E R E A C T I O N ON THE A C T I V I T Y V A L U E S IS OF GREAT I N T E R E S T . T H E

FOLLOWING C A L C U L A T I O N S ARE BASED ON D A T A T A K E N FROM COUGHLIN ( 2 9 ) AND WILL

2 3 ( s )

1 L L U S T R A T E T H E M A G N I T U D E O F T H E E F F E C T :

-2 4-

A G O = +402,300 - 77083T AL203( S ) = 2AL ( L)+3/2 '2 ( G )

~AL(,] = L I A L ( ~ ) A G O = -293,144 + 109.80~

A L 2 0 3 ( ~ ) + 4 A L ( ~ ) = 3 A L 2 0 ( ~ ) A G O = -25,514 - I I .02T (34)

S E L E C T I N G RUN I -P W I T H AN A L U M I N U M SOURCE TEMPERATURE OF 1120°K

(LOG PoAL ( A T M ) = -8.35) WE OBTAIN:

WHEN THE SPECIMENS ARE EQUILIBRATED THE TOTAL PRESSURE P T O T A L

I N T H E S P E C I M E N T U B E WILL BE CONSTANT.

FOR THE SPECIMEN AT 1275°K (SPECIMEN NUMBER I I ) THE FOLLOWING

R E S U L T S ARE O B T A l NED:

p ~ L = 6.25 10-9 - ' A L ~ o = 4.8 x 10-9 ATM

WITH INCREASING TEMPERATURE THE PARTIAL PRESSURE OF ALUMINUM I N EQUIL I -

B R I U M W I T H PA,- 0 WILL SHIFT T O SLIGHTLY HIGHER VALUES. THIS I N TURN 2

WILL CAUSE A S L I G H T I N C R E A S E I N T H E A C T I V I T Y V A L U E S COMPARED TO THOSE

C A L C U L A T E D ON T H E B A S I S OF A U N I F O R M P A R T I A L PRESSURE OF A L U M I N U M THROUGH-

OUT T H E S P E C I M E N TUBE.

FOR S P E C I M E N # I I I N OUR EXAMPLE,THE A C T I V I T Y aAL WOULD BE

.0192 INSTEAD OF .0178, AN INCREASE OF 8%. As THE SPECIMEN TEMPERATURE

APPROACHES T H A T OF T H E A L U M I N U M R E S E R V O I R THE C O R R E C T I O N BECOMES I N C R E A S I N G L Y

-25-

S M A L L E R SO T H A T T H E A C T I V I T Y OF S P E C I M E N S H I G H I N A L U M I N U M I S NOT A F F E C T E D

B Y T H I S S I D E R E A C T I O N . THE R E S U L T S OF OUR E X P E R I M E N T S H A V E BEEN C O R R E C T E D

T A K I N G I N T O A C C O U N T THE F O R M A T I O N OF AL 0. 2

I N T H E PRESENCE OF S O D I U M C H L O R I D E OTHER S I D E R E A C T I O N S ARE

S I N C E THE

I N T H E G A S P H A S E WILL

2 ( G ) ' POSSIBLE, E S P E C I A L L Y T H E FORMATION OF ALCL

ATMOSPHERE I S H I G H L Y R E D U C I N G , T H E AMOUNT OF ALCL 3 B E S M A L L . A C A L C U L A T I O N FOR 1000°K U S I N G E Q U A T I O N

(4 A L C L 3 ( G ) + 2 A L ( G ) = ~ A L C L

A G O = -48,880-t-5 . ~ ~ T L o G T - ~ ~ . 31 T ( 3 5 ) = 2000. THE C O N C E N T R A T I O N OF ALCL I N THE G A S

PALCL 3 3

GAVE A R A T I O

P H A S E WAS THEREFORE NEGLECTED.

I N THE GAS P H A S E H A S B E E N 2 (4 THE P A R T I A L PRESSURE O F FECL

C A L C U L A T E D T O B E O F T H E SAME ORDER O F M A G N I T U D E AS T H A T OF A L U M I N U M I N

THE C A S E OF PURE I R O N SPECIMENS. S I N C E T H E A C T I V I T Y OF IRON I N T H E SUR-

F A C E L A Y E R O F THE S P E C I M E N S D E C R E A S E S R A P I D L Y W I T H T H E A B S O R P T I O N OF

ALUMINUM THE P A R T I A L PRESSURE OF FECL W I L L D E C R E A S E A C C O R D I N G L Y A S THE

E X P E R I M E N T P R O G R E S S E S . THE AMOUNT OF I R O N LOST B Y THE SPECIMENS DUE T O

2

T H I S S I D E R E A C T I O N WAS W I T H I N T H E D I F F E R E N C E O F T H E I R O N CONTENT AS

D E T E R M I N E D B Y C H E M I C A L A N A L Y S I S AND B Y W E I G H I N G OF T H E SPEClME,NS B E F O R E

AND A F T E R T H E RUN. I N A D D I T I O N , N O I R O N WAS FOUND I N T H E A L U M I N U M AT T H E

B O T T O M OF THE S P E C I M E N TUBE AFTER THE RUN. THE R E A C T I O N B E T W E E N THE

WAS THEREFORE U N I M P O R T A N T 2 ( G )

SPECIMENS AND THE GASPHASE T O FORM FECL

AND D I D NOT A F F E C T T H E E Q U I L I B R A T I O N OF T H E S P E C I M E N S .

A S Y S T E M C O N S I S T I N G O F S P E C I E S W I T H D I F F E R E N T MOLECULAR W E I G H T

WILL SHOW WHEN S U B J E C T E D T O A TEMPERATURE G R A D I E N T THE PHENOMENON OF

T H E R M A L D I F F U S I O N , I .E . , T H E C O N C E N T R A T I O N O F T H E S P E C I E S W I T H A S M A L L E R

-26-

MOLECULAR W E I G H T W I L L B E H I G H E R AT T H E H I G H E R TEMPERATURE T H A N AT THE

LOWER ONE. S INCE OUR SPECIMEN TUBE I S A S T A T I C SYSJEM,THERMAL D IFFUSION

WAS P R O B A B L Y F U L L Y O P E R A T I V E . FOR A B I N A R Y M I X T U R E G I L L E S P I E ( 3 0 ) H A S

D E R I V E D T H E F O L L O W I N G E Q U A T I O N :

WHERE XI AND x ARE T H E MOLE F R A C T I O N S AND M AND 2 I M T H E M O L E C U L A R 2

WEIGHTS. R E P L A C I N G THE MOLE F R A C T I O N S B Y THE P A R T I A L PRESSURES AND

R E M E M B E R I N G T H E PToT = CONSTANT THROUGHOUT T H E SPFICI'MEN T U B E WE G E T

FOR A G A S PHASE CONSISTING OF AL AND AL 0 (4 2 ( G ) '

APPL IED T O THE P R E V I O U S E X A M P L E (RUN I - P ) T A K I N G A MEDIAN

= 4.6 x IOm9 ATM, T = 1120°K, AND T2 = 1275'K I = I .65 x 10-9 ATM,

= .004 OR (, pAL l2 = 4.63 x 10-9 ATM

P A L ~ o

DUE T O THERMAL D IFFUSION pAL WOULD I N C R E A S E V E R Y S L I G H T L Y WITH T E M P E R A -

TURE (FROM 4.6 T O 4.63 x IC9 A T M ) BUT THE EFFECT ON THE A C T I V I T Y OF

ALUMINUM I S so SMALL T H A T I T CAN- BE NEGLECTED. SINCE RESULTS FOR THE

RUNS W I T H S O D I U M C H L O R I D E ARE I N GOOD AGREEMENT W I T H THOSE U S I N G A L U M I N U M

ALONE T H E R M A L D I F F U S I O N I S A L S O ONLY O F M I N O R I N F L U E N C E .

SUMMING UP,WE C A N S A Y T H A T THE TOTAL E R R O R IN THE A C T I V I T I E S

OF ALUMINUM IN THE RANGE OF SOLID S O L U T I O N (UP T O 50 ATOMIC $ A L ) SHOULD

NOT E X C E E D - 5$0 THE E R R O R INCREASES W I T H INCREASING ALUMINUM CONTENT

WHICH IS REFLECTED IN THE INCREASE I N S C A T T E R OF THE POINTS IN FIG. 8.

THE GOOD AGREEMENT BETWEEN THE INDIVIDUAL RUNS AND GROSS' RESULTS I S A

+

C O N F I R M A T I O N O F T H I S A S S U M P T I O N .

-27-

VI. DISCUSSION AND CONCLUSION

A S E X P E C T E D FROM T H E Q U A L I T A T I V E C O N S I D E R A T I O N O F T H E P H A S E

D I A G R A M T H E A C T I V I T Y O F A L U M I N U M E X H I B I T S A VERY STRONG N E G A T I V E D E V I A -

TION FROM R A O U L T ' S L A W I N THE RANGE OF S O L I D SOLUTION OF ALUMINUM I N

a-IRON. (FIG. 9 ) . DUE T O THE L A C K OF D A T A BELOW 30 ATOMIC 4& ALUMINUM

T H E E X P E C T E D E F F E C T CAUSED B Y T H E B E G I N N I N G O F O R D E R I N G I N A L L O Y S A T

ABOUT 30-35 A T O M I C $ A L U M I N U M COULD NOT B E OBSERVED. HOWEVER, T H E R A P I D

I N C R E A S E O F T H E A C T I V I T Y O F A L U M I N U M W I T H I N C R E A S I N G C O N C E N T R A T I O N BEYOND

35 A T O M I C $ A L U M I N U M L E A D S T O A VERY LARGE VALUE I N 'At./d NAL N E A R T H E

PHASE BOUNDARY. THIS, I N ADDITION T O THE PRONOUNCED DROP I N ABAL (FIG. 12)

I N THE SAME C O N C E N T R A T I O N RANGE I N D I C A T E S A SHARP I N C R E A S E I N ORDER AS

THE COMPOS I T I ON FEAL ( CSCL - STRUCTURE) I s APPROACHED. THE ST^ I CH I OMETR I c

COMPOSITION FEAL SEEMS T O L I E WITHIN THE ONE PHASE F IELD.

A S M E N T I O N E D B E F O R E , A C T I V I T I E S AND A C T I V I T Y C O E F F I C I E N T S BELOW

30 ATOMIC $ ALUMINUM H A V E BEEN OBTAINED B Y E X T R A P O L A T I O N AND THE A C C U R A C Y

O F T H E S E R E S U L T S I S THEREFORE NOT VERY H I G H . THE SAME H O L D S TRUE FOR A L L

D E R I V E D THERMODYNAMIC P R O P E R T I E S I N T H I S CONCENTRATION RANGE LISTED I N

TABLE x AND P L O T T E D I N FIG. I I AND 12. E S P E C I A L L Y THE A V E R A G E A R V A L U E S AL (27)

( T A B L E I x ) S E E M T O B E TOO H I G H AS COMPARED W I T H T H O S P U B L I S H E D B Y HULTGREN

LESS NEGATIVE Ai,, VALUES I N THE RANGE OF LOW CONCENTRATIONS OF ALUMINUM

WOULD SHIFT THE As,, AND AS M C U R V E ( F I G . 12) T O MORE P O S I T I V E VALUES,

-10 I .E. WOULD D E C R E A S E T H E D E V I A T I O N FROM T H E I D E A L CURVES O F d S A L AND ASM''.

A C O M P A R I S O N OF OUR D A T A W I T H T H O S E OF OTHER I N V E S T I G A T O R S SHOWS,

IN GENERAL,VERY GOOD AGREEMENT. IN FIG. IO THE A C T I V I T Y COEFFICIENTS

DETERMINED B Y GROSS ( I 7 ) AT I193'K ARE PLOTTED AND COINCIDE WITH THE C U R V E

-28-

A

"

C A L C U L A T E D FROM OUR R E S U L T S FOR 1200°K. S I N C E GROSS O B T A l N E D S A T I S F A C T O R Y

AGREEMENT B Y E X T R A P O L A T I N G CHIPMAN'S RESULTS (7'8' 9 9 I FOR L I QU I D I RON-

(27) ALUMINUM A L L O Y S OUR D A T A AGREE ALSO W I T H THOSE OF CHIPMAN. HULTGREN

M PRESENTED D A T A FOR AKAL, A i F E AND A H

O F F O R M A T I O N O F V A R I O U S I N V E S T I G A T O R S ( 1 4 " 5 " 6 ) . THE AHAL FIGURES FOR

S O L I D AND LIQUID ALUMINUM A S THE S T A N D A R D S T A T E A R E SHOWN IN TABLE I X .

AT 2 9 8 " ~ B Y E V A L U A T I N G THE H E A T S

T O COMPARE OUR R E S U L T S W I T H THOSE C O M P I L E D B Y H U L T G R E N ( 2 7 ) A T m H A S T O r~~

B E T A K E N AS ZERO. IN V I E W O F T H E U N C E R T A I N T Y O F T H I S A S S U M P T I O N T H E

AGREEMENT I S R A T H E R GOOD,WITH OUR R E S U L T S B E I N G S L l G H T L Y MORE N E G A T I V E .

I T I S D O U B T F U L I F B E T T E R AGREEMENT CAN B E E X P E C T E D S I N C E T H E ACCURACY OF

E N T H A L P Y D A T A D E R I V E D FROM E Q U I L I B R I U M MEASUREMENTS I S L E S S T H A N T H E

A C C U R A C Y OF D A T A OBTAINED B Y C A L O R I M E T R Y . THERE I S A L S O GOOD AGREEMENT

BETWEEN THE I N T E G R A L E N T H A L P Y OF M I X I N G AH (FIG. 1 I ) AND HULTGREN'S M

VALUE I N TABLE I X .

THE A C T I V I T I E S OF ALUMINUM I N A L L O Y S W I T H MORE THAN 50 A T O M I C $

ALUMINUM SHOW TOO MUCH S C A T T E R (FIG. 8) so THAT AN E V A L U A T I O N OF ISOTHERMAL

A C T I V I T Y - C O M P O S I T I O N CURVES AND A C A L C U L A T I O N O F OTHER THERMODYNAMIC

PROPERTIES H A S NOT BEEN ATTEMPTED. THE D A T A AGREE, HOWEVER, S A T I S F A C T O R I L Y

WITH THOSE OBTAINED B Y GROSS ( I 7 ) AND CAN BE F I T T E D INTO A CURVE G I V I N G

APPROXI MATE ACT I V I T I E S OF ALUMI NUM FOR T H E S E A L L O Y S AROUND 1200°K. THE

REMARKABLE FEATURE OF THIS CURVE IN FIG. 8 I S THE SHARP I N C R E A S E OF T H E

3' A C T I V I T Y IN THE COMPOSITION RANGE OF THE INTERMETALLIC COMPOUND FEAL

THE D A T A FOR THIS COMPOUND SUGGEST THAT FEAL I S STABLE O V E R A LIMITED 3 C O M P O S I T I O N RANGE.

THE RESULTS OF T H I S INVESTIGATION DEMONSTRATE THAT THE METHOD

D E V E L O P E D C A N G I V E R E L I A B L E R E S U L T S WHEN PROPER P R E C A U T I O N S ARE T A K E N .

-29-

ALTHOUGH FURTHER E X P E R I M E N T S WITH SODIUM CHLORIDE W I L L BE NEEDED,THE D A T A

O B T A I N E D S O F A R ARE I N GOOD AGREEMENT W I T H THOSE D E R I V E D FROM E X P E R I M E N T S

WITH ALUMINUM ALONE. ADDITIONS OF NACL SHOULD MAKE I T P O S S I B L E T O EXTEND

MEASUREMENTS T O LOWER TEMPERATURES.

THE MAIN A D V A N T A G E OF THE E X P E R I M E N T A L METHOD USED I N T H I S

I N V E S T I G A T I O N I S T H E S M A L L NUMBER O F RUNS N E E D E D T O O B T A I N THERMODYNAMIC

P R O P E R T I E S OVER A WIDE RANGE O F C O N C E N T R A T I O N AND TEMPERATURE. A S A

M A T T E R OF F A C T O N L Y TWO VERY ACCURATE RUNS W I T H D I F F E R E N T R E S E R V O I R

T E M P E R A T U R E S ARE N E C E S S A R Y T O A C H I E V E T H I S O B J E C T I V E B Y A P P L I C A T I O N O F

E Q U A T I O N 5 .

THE E X P E R I M E N T S C A N BE MODIFIED T O DETERMINE A C T I V I T I E S I N

ALLOYS BELOW 30 A T O M I C $ ALUMINUM W I T H AN ALUMINUM S O U R C E OF LOWER ALUM-

INUM A C T I V I T Y . T H I S C A N BE ACCOMPLISHED B Y THE USE OF LONGER SPECIMEN

T U B E S , G R E A T E R TEMPERATURE G R A D I E N T S OR B Y R E P L A C I N G A L U M I N U M W I T H AN I

A L U M I N U M - I R O N A L L O Y

L A T T E R CASE CARE H A S

ENOUGH AND T H E F I N A L

H A V E A CONSTANT ALUM

P R E F E R A B L Y IN THE FEAL-FEAL~ PHASE F I E L D ) . I N THE

T O B E T A K E N T H A T T H E S U P P L Y O F T H I S A L L O Y I S LARGE

C O M P O S I T I O N I S S T I L L W I T H I N T H E TWO-PHASE F I E L D T O

N U M A C T I V I T Y I N T H E V A P O R P H A S E THROUGHOUT T H E RUN.

OTHERWISE BOTH T H E S P E C I M E N S AND THE ALUMINUM SOURCE WOULD H A V E T O BE

E Q U I L I B R A T E D AND A F T E R T H E R U N , A N A L Y Z E D .

THE METHOD C A N BE APPLIED T O OTHER SYSTEMS E S P E C I A L L Y T O

COMBINATIONS OF R E A C T I V E , HIGH MELTING METALS (T I , ZR, HF, V, NB, TA,

w, MO) AND LOW M E L T I N G M E T A L S W I T H A COMPARATI V E L Y LOW VAPOR PRESSURE

(AL, SN, PB) .

ADJUSTED T O THE P A R T I C U L A R SYSTEM. FOR R E A C T I V E METALS WHERE THE POSSIBLE

FORMATION OF V O L A T I L E SUBOXIDES (E.G. AL 0) MIGHT L E A D T O AN O X Y G E N PICKUP

THE M A T E R I A L OF THE C E R A M I C SPECIMEN TUBE C A N A L S O BE

2

- 30-

851 35

B Y T H E S P E C I M E N S T H E USE O F BORON N I T R I D E (6N) AS A S P E C I M E N T U B E M A T E R I A L

COULD SOLVE THE PROBLEM. AT T H E PRESENT AN I N V E S T I G A T I O N OF THE TITANIUM-ALUMI-

NUM S Y S T E M I S B E I N G C A R R I E D OUT AND T H E R E S U L T S O F T H I S S T U D Y SHOULD PROVE

T H E A P P L I C A B I L I T Y O F T H E METHOD D E V E L O P E D T O R E A C T I V E M E T A L SYSTEMS.

VI I e SUMMARY

THERMODYNAMIC P R O P E R T I E S OF S O L I D IRON-ALUMINUM A L L O Y S H A V E

BEEN DETERMINED I N THE T E M P E R A T U R E R A N G E BETWEEN 900 AND I I o o O C AND FROM

30 T O 75 A T O M I C % ALUMINUM. A METHOD WAS D E V E L O P E D I N WHICH IRON SPECI-

MENS H E A T E D I N A TEMPERATURE G R A D I E N T WERE E Q U I L I B R A T E D W I T H A L U M I N U M

VAPOR FROM AN A L U M I N U M SOURCE K E P T AT T H E TEMPERATURE M I N I M U M O F AN

E V A C U A T E D V E R T I C A L ALL A L U M I N A S Y S T E M . THE ALUMINA SYSTEM CONTAINING

T H E S P E C I M E N S WAS S E A L E D B Y A POOL OF L I Q U I D A L U M I N U M W H I C H S E R V E D S I M U L -

TANEOUSLY A S THE SOURCE OF ALUMINUM V A P O R . AT LOWER TEMPERATURES THE

T R A N S F E R O F A L U M I N U M T O T H E S P E C I M E N S WAS A C C E L E R A T E D B Y A D D I T I O N O F

SODIUM CHLORIDE. NECESSARY EQUATIONS H A V E BEEN WORKED OUT T O C A L C U L A T E

A L U M I N U M A C T I V I T I E S FROM MEASURED Q U A N T I T I E S AND D A T A P U B L I S H E D I N

L I T E R A T U R E

THE A C T I V I T Y OF ALUMINUM I N IRON-ALUMINUM A L L O Y S SHOWS A PRO-

NOUNCED NEGAT I VE D E V I AT I ON FROM RAOULT ' S LAW.

I S APPROACHED THERMODYNAMIC PARAMETERS I N D I C A T E A SHARP I N C R E A S E I N ORDER

A S T H E COMPOS I T I ON FEAL

I N THE RANGE OF SOLID SOLUTIONS OF ALUMINUM I N IRON. THE COMPOSITION OF

FEAL I S WITHIN THE ONE-PHASE F I E L D . USING THE GIBES-DUHEM E Q U A T I O N

P A R T I A L MOLAR P R O P E R T I E S OF I R O N AND I N T E G R A L MOLAR P R O P E R T I E S H A V E B E E N

C A L C U L A T E D FROM 0 TO 50 ATOMIC 5 ALUMINUM AT 1200°K.

-31 -

THE RESULTS H A V E BEEN COMPARED WITH D A T A PUBLISHED I N L I T E R A T U R E

AND GOOD AGREEMENT WAS FOUND. THE METHOD SHOULD BE APPLICABLE T O SYSTEMS

WHICH CAN B E I N V E S T I G A T E D ONLY W I T H D I F F I C U L T Y B Y OTHER E X P E R I M E N T A L PRO-

CEDURES. ONE MAIN ADVANTAGE I S THE SMALL NUMBER OF E X P E R I M E N T S N E C E S S A R Y

T O OBTAIN RESULTS O V E R A WIDE RANGE OF COMPOSITION AND TEMPERATURE. THE

V A R I O U S SOURCES OF ERRORS HAVE B E E N D I S C U S S E D TO ASSESS T H E ACCURACY OF

THE R E S U L T S AND T H E R E L I A B I L I T Y O F T H E METHOD.

.

-32-

V I I I . REFERENCES

I .

2. M. HANSEN AND K. ANDERKO:

A. J. BRADLEY AND A. H. JAY: PROC. ROYAL SOC., 1932, VOL. ~ 1 3 6 , P. 210.

"CONSTITUTION OF BINARY ALLOYS," 1958, MCGRAW-HILL, NEW YORK.

3. J. R. LEE:

4.

J. IRON STEEL INST., 1960, V O L . 194, P. 222.

A. TAYLOR AND R. M. JONES: J. PHYS. CHEM. SOLIDS, 1958, VOL. 6, p. 16. 5. W. A . MAXWELL: PROC. SECOND UNITED NATIONS INTERNATIONAL CONFERENCE

ON THE PEACEFUL USES OF ATOMIC ENERGY, U.S. GOVT. PRINTING OFFICE, 0-469588 (J-I462), 1958.

PATENT 2,198,673 (1940); P. GROSS, U.S. PATENT 2,470,305 (1949). 6. C. B. WILLMORE, U.S. PATENT 2,184,705 (1939); K. LOEWENSTEIN, U.S.

7. TRANS. AM. SOC. METALS, 1934, VOL. 22, P. 385.

8. J. CHIPMAN: DISC. FARADAY SOC., 1948, No. 4, P. 23.

9. J. CHIPMAN AND T. P. FLORIDIS: A C T A MET., 1955, VOL. 3, P. 456.

J. CHIPMAN:

I O . J. CHIPMAN AND F. C. LANGENBERG: "THE PHYSICAL CHEMISTRY OF STEEL-

I I . Y. CHOU AND J. ELLIOTT: A C T A CHIM. SINICA, 1956, V O L . 22, P. 23.

MAKING," 1 958, TECHNOLOGY PRESS, M. I .T.

12. T. c - W i L D E R AND J. ELLIOTT: J. ELECTROCHEM. SOC., 1960, V O L . 107, P. 628.

13. 14. W. BILTZ AND C. HAASE:

P. 141.

R. D. PEHLKE: TRANS. AIME, 1958, VOL. 212, P. 486.

Z. ANORG. ALLGEM. CHEM., 1923, VOL. 129,

15.

16. 0. KUBASCHEWSK~ AND W. A. DENCH: A C T A MET., 1955, VOL. 3, P. 339.

17. P. GROSS, D. L. LEVI, E. W. DEWING AND G. L. WILSON: INTERNATIONAL

W. OELSEN AND W. MIDDEL, MITT. KAISER-WILHELM-INST. EISENFORSCH. (DUESSELDORF), 1937, VOL. 19, P . I .

SYMPOSIUM ON THE PHYSICAL CHEMISTRY OF PROCESS METALLURGY, PITTSBURGH, 1959.

18. P. GROSS, C. S. CAMPBELL, P. J. C. KENT AND D. L. LEVI: DISC. FARADAY SOC., 1948, No. 4, P . 206.

-33-

REFERENCES (CONTINUED)

19. P. HERASYMENKO: ACTA MET., 1956, VOL. 4, P. I.

20. W. F. ROESER AND S. T. LONBERGER: NBS CIRCULAR 590, 1956.

2 1 . C. B. WILLMORE: U.S. PATENT 2,184,705, 1939.

22. P. GROSS: PROC. CONGR. INTERN. ALUMINIUM, PARIS, 1954, VOL. I , P, 167.

23. 0. KUBASCHEWSKI AND E. LL. EVANS: "METALLURGI C A L THERMOCHEMISTRY,"

24. R. E. HONIG: RCA REVIEW, 1957, VOL. 18, P. 195.

1958, PERGAMON PRESS, NEW YORK.

25. E. W A L D S C H M I D T : METALL, 1956, No. 23/24, P. 1126.

26. J. F. ELLIOTT AND M. GLEISER: "THERMOCHEMISTRY OF STEELMAKING,"

27. R. HULTGREN (PROJECT SUPERVISOR): SELECTED VALUES FOR THE THERMO-

1960, ADD I SON-WESLEY PUBL, READ I NG.

D Y N A M I C PROPERTIES OF METALS AND ALLOYS, MINERALS RESEARCH LABORATORY, BERKELEY, CALIF .

28. L. BREWER AND A. W. SEARC:Y: J. AMER. CHEM. SOC., 1951, VOL. 73, P. 5308.

29 . J. P. COUGHLIN: "CONTRIBUTIONS T O THE DATA ON THEORETICAL METALLURGY. X I I ,I' BUREAU OF MINES BULL. 542, 1954.

30. L. J. GILLESPIE: J. CHEM. PHYSICS, 1939, VOL. 7, P. 530.

, - 34-

TABLE I

RUN I ( A L U M I NUM-SOD I UM CHLOR I D E )

4

t

SPEC I MEN No.

20’

7 I

I 2 I ‘ 3 12 I I

10

%

TEMP E RAT u RE OK.

I 178 I I go I201 121 I 1221

1223 12 0 I 252 I 260 I 267

I 272 1 7 7 12 1 1 284 I 287

-LOG a~~ AL a

RESERVOI R TEMPERATURE OF I I I O O K .

0.654

22 ,936

I ,018

I .to6 I . i82 I .270 I -332 I -396 I .438

I .496 I .521 I .546

I .471

0.222 . I 76 I42 . I 16

.0960

*0284 *o 57

*OZ32 *o 7

*0368

.Ob02

0033 -031 9 ,030 I ,0287

AL CONTENT A T O M I C PERCENT

3.32 3.5 2.70 I .46 0.35 0.69 0.49 I .29 0.22 0.64

- 35-

TABLE I I

SPEC I MEN

No.

SPACER 20

I 7" 16-

I 3" 12-

I I * IO-

RUN 3 ( A L U M I N U M )

PAL TEMPERATURE 4

J O MM a~~ - "K

15.8 .067n I 7.8

21. 23.4

13d5 13 2 I387 1391 I 395

1 9 3

24.0 .Ob40 I ' ;1$ 01 25.0 .ob24

AL CONTENT A T O M I C PERCENT

1%*5J 1 .o 13.94 I I .98 9.90 8.62 7.36 2: 3 6.04

5 -25 4.50

* I N I T I A L C O M P O S I T I O N OF S P E C I M E N : FE-16% AL; O T H E R S P E C I M E N S : PURE I R O N .

- 36-

TABLE I I I

RUN I -K (ALUM I NUM-SOD I UM CHLOR I DE )

AL CONTENT ATOMI c PFRCFNT z~ L

SPEC I MEN TEMP E RAT u RE -LOG ai: No. O K - -

RUN I - K ' K- I K - I * K-2 - K-2" K-3-

K-4" K - 5 - K-5"

RUN I - K " K- l 1 " K.? 12 - K-12"

1134 1155 1175 I 196 1216

0.220 .413 591 ' 772 937

I 209 2.052 I .918 I 4 0 1 I 16

1193

0.628 .386 .256 .169 .I 16

76.2' 75. 5 71 .bo 51 .66 50.00

,0845 48.79

.o 4 38.77 *0374 34 92

-- -- 42.21

* IN IT IAL COMPOSITION OF SPECIMENS, F~-16$ AL; OTHER SPECIMENS: PURE IRON.

** A C T I V I T Y VALUES FOR SPECIMENS NO. K - l T O K-5* WERE CALCULATED USING

A RESERVOIR TEMPERATURE OF Illl'K. (RUN I-K!); THE A C T I V I T Y VALUES

TEMPERATURE OF 1003"~.- RUN I-K") . FOR S P E C I M E N S NO. K-11" T O K-12" WERE C A L C U L A T E D U S I N G A R E S E R V O I R

-37-

831 42

TABLE I V

RUN I-N ( A L U M I N U M )

I

i

SPEC I MEN

No. N- I N - I * N-2 - N-2" N-3-

N- N-$* N-4* N-5 - N-5* N-6 N -6*

N-7" N-7 -

AL

K. 5 aAL 080 0.107 086 .126 I 00 * 20(' * 389

.229

.io7 I 18 ' 339 1 39 725

TEMPERATURE 10 MM

o:2;i

161

I 192 I 198 1 1 Ii5 3

I 203 I 205 I 205 I 203

.04 -O6l6 8 I .15 I .66 2.04 .0380 2-57 .0302 3.02 -0257

3-47 3.63 3-63 3-47

.022 4

.02 I4

.0214

.0224

AL CONTENT A T O M I C P F ~

76.64 76.42

72.48 71 -25

-9

z;:: 46.36 45.10 43-71 43.17 42 *55 41.30 41.7

* I N I T I A L C O M P O S I T I O N OF S P E C I M E N S , F ~ - 1 6 $ AL; OTHER S P E C I M E N S : PURE

- I R O N

AL R E S E R V O I R TEMPERATURE I 070'~. (poAL = 7.76 10'7 M M ) .

-38-

.Q TABLE V

RUN 1-0 ( A L U M I N U M )

SPEC I MEN No.

I 2

2

i!

5 6

9 IO

I I 12

TEMPERATURE "K

I 183. I 1201.6 1227. I 1252.6 I 275.6

I 306. I 1316.1 I 9 4 . 6

1332.1

1294. I

1330. I

1331 . I

PO*L

10 5 MM

2.09

I I .22 ' 9.05

28.18

66.07 66.07

a~~

I o2

?:% 3.3' 2.76 2.51

2.35 2-35

-39-

AL CONTENT ATOMI c PERCENT

72.2 72.4

45.4

41. 42 3 3%*2

3 l ' I

3 - 3

3 07

TABLE V I

3

- SPEC I MEN

No.

I 2

:

i

5 6

9 IO

I I 12

RUN I - P ( A L U M I N U M )

a POAL AL

O K 10 5 MM I o2 TEMPERATURE

60.71 38 43

I ii?:! 3.55 I 9. *? 4 I 223. I 5 * 2 5 6 4 5

12;: I 1261.6 1269. I 12-73. I

7-94 10.23

I .60 18.62

12.49

4 3 7 3. 2 2.66 2.19 1-97

1275. I 7 . 0 5 I .92 1273.6 I .62 1-97

, -b

AL R E S E R V O I R T E M P E R A T U R E : 1120°K (poAL = 3.4 x 10 MM)

AL CONTENT A T O M I C PERCENT

37.4 37.5

SPEC I MEN NO

I 2

; 5

i 9 IO

I 1 12

TABLE V I I I

RUN I-s ( A L U M I N U M - S O D I U M C H L O R I D E )

TEMPERATURE LOG 'aAL O K

- I 9396 I ,106 2.780

I 168. 2 *297

I 187.6 - 2.116 1202.1 1215. I 1225. I 3.81 4 1231.6 3.766

- 2.514

-

::gi

AL-NACL R E S E R V O I R T E M P E R A T U R E : IO03 O K .

a AL

102

3 . 3

24.89 I 2.76 6.03

I - 9

I .31 I .02

0.55 0.52

AL CONTENT - 69.6 65.6

41.9 ?;:; 38.8 34.6

2 .6 3 d - O

27.4

n

- c

-- --

-15,400

-16,000

-12,400

- TABLE I X

R E L A T I VE PART I AL MOLAR ENTHALPY OF ALUMI NUM ( AmAL)

-- -16,500

- I I ,800

- I 3,900

--

-- -- I -- --

40.

I -R

-- -- -- - I 5,800

-13,100

-12,200

- I 4,900

I -s L-

c-

-- - I 7,500 - I 6,000

-15,500 - I 4,000

A V E R A G E VALUE

- 1 7,900 -I 7,200

- I 6,300

-16,100

- I 4,900

- I 3,400

-I 2,300

(27)

(4 - I 2 , 700 - I 3,600

-13,100

- 12,500

-I I ,700

- I 0,600

-9,500

AL (d

-15,600

-15,100

- 1 3, 700

- I 2,600

-I I ,500

AL

-14,700

- 14,500

-43-

TABLE X

THERMODYNAMIC P R O P E R T I E S OF IRON-ALUMINUM A L L O Y S

AT 1200°K

. I O

- 1 7,900 -15,700

-2 .oi 5 -16,550 -17,190 - I I ,070

- I . I2 + I .28

-3.01 5

t4.57 -3.29

- .0507

-280

-1,980

-50

-I ,620 t.30

- 0047

20

- I 7,200 - I 5,000

- I ,850 -2 550

-I 4,000

-I 4,640 -10,160 -2.67 -0.27

i3.20

-3.47 - e0273 -. 1243

-680

-3,490 -200

-3, 160

CONCENTRAT I ON (NAL)

30

- I 6,300

-2.182

- I .660 - 12,000

- I 2,640 -9, I I O

-3.58 - I . 18

i2.50 -3.68

- .2501

-1,370

-650

-14,100

-.0951

-4,750

-4,680 i.06

~~

35

- 1 6 , io0

- 1 3,900 - I ,987 - I ,532 -10,900

- 1 1,540 -8,410 -4.33 - 1 093 t2.09

-. 1628 - 3498 -I .920

-930 -5,460

14

-4.02

-5,290

.40

-14,900 - I 2,700

- 1 e 3 7 3 -9,720 -10,360 -7,540 -4.33 - 1 *93 +I .82

-3.75 - 02773

-2,740

- I a771

- 4993

-5,820 - I , 5 1 c

-5,980 - . 1 3

45 -I 3,400 - I 1,200

- I 0467 - I . I 19 -8,050 -8,690

-4.45 -2.05

+I -59 -3.64 -.448I

-6,140

-.7081

-6,020

-2,220

-6,260

-3,890

- .20

-50 -12,30 - 1 0 , l O

- I . I 1 9 -0.818

-6,780

-5.13 -2-73 ti .38

-.721 I - I ,022

-5,600

-6, I 90 -3,280

-6,690

-6,140

-4,500

-4.1 I

-.42

STANDARD S T AT E

“Q -44-

WE16Hl PER CENT ALUMINUM

$1

w

700 YAGN. TRANSF.

h A T O N I C PER C

1 I I I I 1 I I I

I I I c-- I I I I

I I I t I I I I

s--

r

- 1 60 ro N T A L U N I N U Y

FIGURE 1 . IRON-ALUMINUM PHASE D I A G R A M

90 1 0 AL

.Q

3

1

l -

6

16;'

NOTE: THESE TWO f; 5 " X 5" 4

THREADED ALUMINUM /- ROO WITH NUT

f BOTH TUBES 0.D.g

II I,

I$ x I$ DIA. BRASS BELLOWS

4 T D I A . X $ THICK

RUBBER QUAD RING SEAL 3$ LO. X 4"O.D.

$'X 5" X 5" ( R C ) BRASS TOP PLATE

PLATES ARE HELD TOGETHE BY FOUR DIA. THREADED ALUMINUM RODS THESE RODS ARE NOT SHOWN HERE.

BRASS RINGS

WILSON SEAL. FEMALE HAS I" 0.D

TO VACUUM PUMP -

PYREX CYLINDER 29" X 4"O.D. X 3 g I . D .

TUNGSTEN TIP &'DIA. x $' - 2f HIGH X 2$ O.D. WITH $ WALL Et BOTTOM. 4 TAPS 90" APART FOR T D I A . BRASS BOLTS

,- f' DIP, x 3'-6" LONG STEEL ROD

,---RUBBER O-RING

SCALE APPROX. 6"; I '_ 0"

FIGURE 3. U N I T FOR A R C W E L D I N G I R O N R E A C T I O N TUBES

INVERTED ALUMINA TUBE

J

ALUMINA CRUCIBLE

VACUUM r ALUMINA SPACER

/-

,r SPECIMENS

-SODIUM CHLORIDE

- ALUM I NUM

/- ALUM IN A "CHUNKS"

FIGURE 4. A L U M I N A R E A C T I O N TUBE (BEFORE MELTING A L U M I N U M )

891 52

3

NaCl

AI

INCREASING TEMPERATURE-

FIGURE 5 . ALUMINA R E A C T I O N TUBE ( A F T E R M E L T I N G A L U M I N U M )

53

‘4. KEY: - SPEC IN1 TI

c

MEN TEMPERATURES GIVE1 AL SPEC1 M EN COMPOSITIOF

0 PURE F€ X Fe-16 O/o AI

0.30

0.25

0.20

0.15

0.10

0.05 1267 1277

0

AI -NaCI RESERVOIR (1110 O K )

IN O K

>

0 1178

0‘1331 f AI (1250 RESER\ O K

19

LAW /

I IR

0 5 IO 15 20 25

ALUMINUM CONTENT, ATOMIC PER CENT d

FIGURE 6 . A C T I V I T Y OF ALUMINUM A S A FUNCTION OF C O M P O S I T I O N AS D E T E R M I N E D B Y E X P E R I M E N T A L RUNS I N I R O N R E A C T I O N TUBES

89% 5 4

3

.I8

.I7

.I6

.I5

.I4

.I3

-12

. I I

*IO

.09

.08

.07

.06

.05

.04

.03 ~

I I I I I I I I I I

R AOU LT'S

K E Y : - + RUN I - N

x RUN 1-0 0 RUN I -P

0 RUN I -R

A RUN I -S

13220 I

0 5 IO 15 20 25 30 35 40 45 50 55 60

ALUMINUM CONTENT, ATOMIC PERCENT

FIGURE 7. A C T I V I T Y O F ALUMINUM AS A FUNCTION OF C O M P O S I T I O N AS DETERMINED B Y E X P E R I M E N T A L RUNS IN ALUMINA R E A C T I O N TUBES

891 55

I .o

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0. I

0

1193 0 I ' I I '

I I I

I I I I

30 40 50 60 70 80 90 100 I

ALUMINUM CONTENT, ATOMIC PERCENT

FIGURE 8. A C T I V I T Y OF A L U M I N U M I N I R O N - A L U M I N U M A L L O Y S FROM 30 T O 100 A T O M I C PERCENT A L U M I N U M

.J

1

.20

.I9

.I8

.I7

.I6

.I5

.I4

.I3

.I2

. I I

.IO

.09

.O 6

.07

.O 6

.05

I I I I I I 1 ) ! 1 1 I

I

KEY: - f 1 2 0 0 ° K 0 1 3 0 0 ° K 0 1 4 0 0 ° K

ALUMINUM CONTENT, ATOMIC PERCENT

FIGURE 9. A C T I V I T Y O F ALUMINUM I N IRON-ALUMINUM A L L O Y S FROM 0 T O

50 ATOMIC PERCENT ALUMINUM

i

I I

0 - I I I I I I

b

h 1

F

3

I KEY : - + 1 2 0 O 0 K

0 1300’K

0 1400’K

0 I193 K (GROSS)

i

ALUMINUM CONTENT, ATOMIC PERCENT

FIGURE I O . A C T I V I T Y COEFFICIENTS OF ALUMINUM I N IRON-ALUMINUM ALLOYS FROM 0 T O 50 ATOMIC PERCENT ALUMINUM

- 15,000

Zi p - 10,000

i

\ ‘9

I I I I I \

I I 1

‘0, \

\ \ \

\ \

ALUMINUM CONTENT, ATOMIC PERCENT

F I G U R E I I . THERMODYNAMIC P R O P E R T I E S OF I R O N - A L U M I N U M ALLOYS AT 1200’K

I (3

a

i U

\ -J

0

v, 0 c

a U

t a 0 -I LT I- z w

-2

-3

z X

X \

\ X

\

- A3A1 '+ \ \

1 1 I 1 I I I I I

60 80 too 20 40

ALUMINUM CONTENT, ATOMIC PERCENT

F I G U R E 12. MOLAR A N D P A R T I A L MOLAR ENTROPY OF IRON-ALUMINUM ALLOYS AT 1200°K