alustar armour plate.0.8 1´1´ alustar tm a strong material for marine and armor plate applications

ALUSTAR Armour Plate.0.8 1

´

ALUSTAR TM A Strong Material

ForMarine and Armor Plate

Applications


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ALUSTAR TM A Strong Marine & Armor Plate Material

• AL-Mg Alloys in General: Among all aluminum alloys, the non-heat treatable Al-Mg alloys (5xxx series) are the most suitable material for marine applications. Magnesium, as the main alloying constituent, lends itself to reasonable strength for marine applications. More important, however, is the corrosion resistance of Al-Mg alloys which makes them the most suitable material for shipbuilding.

• Effect of Mg on Strength: The relationship between Magnesium content of 5xxx alloys and its mechanical properties, i.e. yield strength, tensile strength, and elongation, is given in slide 7. The main reason for increasing strength is the formation of Al-Mg intermetallic particles which reinforce the alloy.

• Effect of Mg on Corrosion Resistance: Theoretically, increasing the Mg content will add to strength. However, when Mg% is raised above approximately 4%, the corrosion resistance of the alloy will gradually decrease. The reason for this phenomenon is that at higher Mg%, the Al-Mg intermetallic particles will start precipitating at the grain boundaries. These particles are anodic relative to Aluminum and thus they cause electrochemical imbalance in the grains which leads to “Inter Granular Corrosion”. This causes pitting and weight loss. Furthermore, IGC may lead to “Stress Corrosion Cracking”.


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• Alloys AA5083 and AA5456: Alloy 5083 has been a popular shipbuilding alloy for a couple of decades. With the average Mg content of 4.4%, it provides a yield strength of 31 KSI, ultimate tensile strength of 44 KSI and an elongation of 10%. The corrosion resistance of AA5083 has been quite satisfactory for marine applications. However, the need for a higher strength marine alloy gradually became apparent as more aluminum vessels were built; specially for fast ferries and catamarans where weight saving and higher speed became an important issue. An alternative high strength alloy was AA5456 which is mainly used for military applications and coast guard vessels. The Mg level in this alloy is up to 5.5% which produces a yield strength of about 35 KSI and UTS of about 48 KSI with somewhat lower elongation (less formability). However, the lower corrosion resistance became evident as no special treatment for corrosion resistance was done. Although this alloy is still recommended in military and government specifications, Its use has drastically affected the design and maintenance of the vessels. For example, coast guard rescue bots made of this alloy have a very tight service interval. Also, for vessels operating in sea water (salt water), the lower part of the hull is painted with multiple layers of epoxy paint.


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• Alloy AA5383: Alloy AA5383 was developed in the nineties, in an effort to increase strength. The Mg content of this alloy is slightly higher than that of AA5083 and this has increased the yield strength to 32 KSI or 220 MPa (about 1 KSI more than AA5083) while the UTS and Elongation remain the same. The yield strength and UTS after welding is 20 KSI and 42 KSI respectively and this is about 2 KSI higher than AA5083. There has been no official reports of reduced corrosion resistance as due to minimal increase in Mg content and strength, the difference in corrosion resistance with that of AA5083 may appear in several years. We are aware of one case where this alloy was used in a Catamaran which was exposed to elevated temperature (200 F) for a couple of months (the vessel was under extreme sunlight) and significant amount of pitting was reported. This was attributed to sensitization due to added Magnesium. Currently, several vessels made of AA5383 are in service. However, the slight increase in strength has not been used for down gauging and subsequent weight saving.


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• Alloy AA5059 ALUSTAR: In the development of Alustar, we had two major goals; 1) Increase strength, both before and after welding, by at least 20% so that the user can use a thinner gauge and thus build a lighter vessel or alternatively build a vessel with 20% higher overall strength, and 2) keep the corrosion resistance at the same level or better than that of AA5083.

• Strength: By adding up to 6.0% Mg, and subtle amounts of Zr and Mn we can guarantee a minimum yield strength of 270 MPa (39 KSI) and UTS of 370 MPa (53 KSI), while elongation (which lends itself to formability) remains at 10%.

• Corrosion resistance: By the application of a proprietary thermo-mechanical process and the addition of controlled amount of Zn we were able to keep all the major intermetallic particles inside the grain and prevent any excessive electro-chemical imbalance and thus avoid corrosion susceptibility. Extensive corrosion tests performed and documented under the supervision of classification societies such as DNV show that the corrosion resistance of Alustar is better or equal to that of AA 5083.

• Weld Properties: We have also been able to improve welding and heat affected zone (HAZ) strength by controlling the re-crystallization rate during welding and to avoid the formation of large grains.


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AA5083 Alustar[Weight%] [Weight%]

Mg 4.0-4.9 5.0-6.0

Mn 0.4-1.0 0.6-1.2

Zn 0-0.25 0.4-1.5

Zr - 0.05-0.25

Cr 0.05-0.25 0-0.3

Cu 0-0.10 0-0.4

Fe 0-0.4 0-0.5

Si 0-0.4 0-0.5

Alloying Constituents

CHEMISTRY



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0

100

200

300

400

0 2 4 6 8 10

Mg-Content [Ma.-%]

UT

S, Y

TS

[M

Pa]

25

30

35

40

45

El. [

%]

UTS

YTS

El.

Polynomisch (YTS)Polynomisch (UTS )Polynomisch (El.)

Alustar: Influence of Magnesium ContentOn YS, UTS, and Elongation (5xxx alloys)

58 KSI

43.5 KSI

14.5 KSI


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CORROSION RESISTANTMICROSTRUCTURE

AA 5083 / H321 TEMPER

SUSCEPTIBLE TO IGCCORROSION


In Principle, increasing the Mg content In Aluminum Magnesium alloys will increaseStrength. However, beyond 4.5% Mg, the Corrosion resistance decreases, due to Precipitation of ANODIC Al-Mg IntermetallicParticles at the grain boundaries. The alloy thenBecomes susceptible to inter-granular corrosion.Using controlled amounts of Zn will createMg-Zn intermetallics which in combination ofSpecial thermo-mechanical processes, will stayInside the grains and compensates for the electro-chemical imbalance. Mn and Zr are also added in controlled amounts to add strength and delay the process of re-crystallization in the HAZ to produce a fine grain structure after welding


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PHYSICAL PROPERTIES

PROPERTIES AA5083 Alustar

Density at 20°C [g/cm³] 2.66 2.64

Approximate Melting Range [°C] 574-638 568-636

Coefficient of Linear thermal 20-100°C 24.2 23.0

expansion 20-200°C 25.0 24.5

[µm/m.K] 20-300°C 26.0 25.9

Specific heat at 20°C [J/kg.K] 900 890

Electrical conductivity at 20°C [%IACS] 29 27.1

Electrical resistivity at 20°C [µWcm] 5.95 6.3

Physical Properties of AA5083 and Alustar Alloys



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MINIMUM TENSILE PROPERTIES TEMPER: H321 / H116

21

5

30

5

10

22

0

30

5

10

27

0

37

0

10

0

50

100

150

200

250

300

350

400

0

5

10

15

20

25

30

35

40

EL

ON

GA

TIO

N (

%)

ST

RE

NG

TH

(M

Pa)

AA5083 AA5383 ALUSTARE

long

atio

n

Elo

ngat

ion

Elo

ngat

ion

YS

UT

S

UT

S

UT

S

YS

YS

Thickness Range 2-20mm


31KSI

44KSI 32

KSI

44KSI

39KSI

53KSI


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STATISTICS

Tensile Properties of Several Lots of H321 Temper Alustar Alloy Material

5 10 15 20 25

4 mm

5 mm

6 mm

7 mm

8 mm

9 mm

10 mm

12 mm

14 mm

16 mm

25 mm

32 mm

Gau

ge

Elongation [%]

Min 10 %

350 375 400 425

4 mm

5 mm

6 mm

7 mm

8 mm

9 mm

10 mm

12 mm

14 mm

16 mm

25 mm

32 mm

Gau

ge

Ultimate Tensile Strength [MPa]

> 20 mm:Min 360 MPa

< 20 mm:Min 370 MPa

250 270 290 310 330

4 mm

5 mm

6 mm

7 mm

8 mm

9 mm

10 mm

12 mm

14 mm

16 mm

25 mm

32 mm

Gau

ge

Proof Strength [MPa]

> 20 mm:Min 260 MPa

< 20 mm:Min 270 MPa



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After WELD STRENGTH

140

290

160

300

125

275

UT

S 0

50

100

150

200

250

300

YS

YS

UT

S

YS

UT

S

ALUSTARAA5383AA5083

ST

RE

NG

TH

(M

Pa)

MIG-welded Plates in H321 with AA5183 Filler Wire


18 KSI

40 KSI

20 KSI

42 KSI

23 KSI

23 KSI

43.5 KSI


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After WELD STRENGTH

Typical Tensile Properties Obtained from Cross Weld Tensile Tests

270 320

6

8

10

16

35

40

Gau

ge[m

m]

UTS [MPa]

125 175 225

Gau

ge[m

m]

Yield Strength [MPa]

6

8

10

16

35

40

ALUSTAR TM Material


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HAZ

WELD POOL METAL

BASE PLATE [ALUSTAR]

FUSION LINE

BASE PLATE [ALUSTAR]HAZ

Grain Structure Modification by Welding

By the addition of controlled amounts of

Zr and Mn re-crystallization during welding

Is delayed and a finer grain structure is achieved

WELD STRUCTURE



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Hardnessprofile of MIG - welded Alustar H321 and AA5083 H321

65

75

85

95

105

115

125

135

0 10 20 30 40 50 60

ALUSTAR (H321, t = 8 mm)

AA 5083 (H321, t = 8 mm)

Distance to the middle of weldseam (mm)

Har

dn

ess

( H

V 5

)


½” 1.0” 1.5” 2.0”


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MIG - WELDING AND SIDE BEND TEST

Alustar MIG-welded with Filler Wire AA 5183



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FORMABILITY

100

150

200

250

300

350

0 5 10 15

Additional Cold Reduction [%]

Pro

of S

tren

gth

[MP

a]ALUSTAR

5083

Poly. (ALUSTAR)

Poly. (5083)

250

275

300

325

350

375

400

0 5 10 15


UT

S [M

Pa]

ALUSTAR

5083

Poly. (ALUSTAR)

Poly. (5083)

5

10

15

20

25

30

0 5 10 15


Elo

ngat

ion

[%]

ALUSTAR

5083

Poly. (ALUSTAR)

Poly. (5083)

Influence of Strain Hardeningon Alustar and 5083 by Cold Deformation on Formability



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BENDABILITY

Photomacrograph Showing the 8mm Gauge Alustar Alloy Samples after Bend Test



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CORROSION TEST METHODS

ASSET Test [ASTM G66]

Measures Pitting and Exfoliation ResistanceMaterials Tested : Unwelded / Welded / Various Gauges

Sensitized and Un-sensitized

Weight Loss Test [ASTM G67]

Assesses Intergranular CorrosionMaterials Tested : Unwelded Plate / Various Gauges

SCC [ASTM G39/AIR 0948-147]

Materials Tested : Unwelded / Welded / Various GaugesSensitized and Un-sensitized



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CORROSION TEST

ASSET Corrosion Test Results before and after Welding of AA5083 and Alustar

Plate Welded Panel

AlustarAA5083 AlustarAA5083MIG-welded with AA5183



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CORROSION TEST

Surface of Sensitized Samples after the ASSET Test



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STRESS CORROSION

Method:Intermittently Immersion in 3,5% NaCl (AIR 9048 Test).Applied Stress (LT): 195 N/mm2 (130 N/mm2 Welded)Gauge Thickness: 8, 10, 12, 16, 20, 25 mm.

Material:Alustar sensitized for 7 days at 100º C

Result:No SCC after 8000 hours



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(7)50

(13)90

(19)130

(24)170

1,00E+

05

2,10E+

06

4,10E+

06

6,10E+

06

8,10E+

06

1,01E+

07

NUMBER OF CYCLES

ST

RE

SS

(K

SI)

MP

a

ALUSTAR/AA5183

AA5083/AA5183

FATIGUE AFTER WELDINGS-N Curves



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SUMMARY

Mechanical Properties, Fatigue and Impact More than 20% better than AA5083 before and after Welding

Corrosion Resistance Better or equal as AA5083 before and after Welding and in Sensitized Condition

Formability, Weldability, Toughness and Physical Properties Comparable to AA5083

Consistent Quality and Manufacturing Experience Several Thousand Tons in Fast Ferry, Military and Yacht Applications

Approvals from Major Classification Societies Improvement of Design Criteries by Fatigue Testing on Construction Details

ALUSTAR TM A Strong Marine & Armor Plate MaterialALUSTAR TM A Strong Marine & Armor Plate Material


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• For Further Information:-

• Tel:- +44 20 7681 1505

• Fax- +44 870 168 0554

• Email:- [email protected]

• Websites:- www.aluminumnow.com www.catamaranferries.com

alustar armour plate.0.8 1´1´ alustar tm a strong material for marine and armor plate applications

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