dr.r.narayanasamy, dr.s.sivasankaran and dr.k.siva prasad on mechanical alloying

Study on Synthesis, Characterization and Workability behavior of nanocrystalline

AA6061 alloy reinforced with TiO2 Composite prepared by Mechanical alloying

ByS.SIVASANKARAN

414108054

Research Supervisor Dr.R.NARAYANASAMY,

Professor,Department of Production

Engg.,NIT, Tiruchirappalli - 15

Research Co-SupervisorDr. K.SIVA PRASAD, Assistant

Professor,Department of Metallurgical and

Materials Engg.,NIT, Tiruchirappalli - 15

Doctoral Committee Members

External Member Dr. G.Chandramohan, Retired Professor,Dept. of Mechanical Engg.PSG College of Technology, Coimbatore – 641 004

Internal MemberDr. V. Senthil Kumar, Assistant Professor, Dept. of Production Engg.,NIT, Tiruchirappalli - 15

ChairmanDr.T.SELVARAJ, Professor,Dept. of Production Engg.,NIT, Tiruchirappalli - 15

Internal MemberDr. C. Sathiya Narayanan, Assistant Professor,Dept. of Production Engg.NIT, Tiruchirappalli - 15

Research Supervisor Dr.R.NARAYANASAMY, Professor,Dept. of Production Engg.,NIT, Tiruchirappalli - 15

Research Co-SupervisorDr. K.SIVA PRASAD, Assistant Professor,Dept. of Met. and Materials Engg.,NIT, Tiruchirappalli - 15

Outline of Thesis presentation1) Introduction2) Literature review3) Research Gap, Problem defined, Objectives

and Work plan4) Experimental procedure5) Results and Discussion

5.1. Powder surface morphology evaluation5.2. Flow characteristics of powders5.3. Structural evaluation of mechanically alloyed powders5.4. Compressibility behavior of micro and nanocomposite powders5.5. Evaluation of compaction equations5.6. Green mechanical strength and sintering behavior5.7. Grain refinement and its formability5.8. Trimodaled nanocomposite and its formability5.9. Modeling of compaction behavior using ANFIS

6) Conclusions and Scope for future work 7) Publications and References

1.0 IntroductionComposite Materials – DefinitionMetal matrix composites (MMCs)

The process of embedding various reinforcements such as SiC, or Al2O3

or TiC or AlN etc.. on the metal matrix in order to improve the properties

of metal(s) called MMCs

Metal MatrixCeramic Particles (high strength

high stiffness high thermal stability)

Fig. Particulate MMCs

4

Why MMCs?Because they offer following properties - High specific strength - High specific stiffness - High specific modulus of elasticity - Light weight - Good corrosion resistance - Excellent wear resistance - Good fatigue resistance - Low coefficient of thermal expansion

- Particulate Al-MMCs [Combined metallic and ceramic properties]- The high strength Al alloys with applications in aircraft and automated

industry are 6xxx series- This 6xxx series alloys have good formability and heat treatable alloy- Methods for Manuf. MMCs [P/M, Stir casting, in-situ, pressure infiltration

etc..]- P/M route (Avoiding detrimental reaction between matrix and dispersoid /

reinforcement, Possibility of adding higher amount of reinforcement, Controlling the

microstructure and uniform distribution)- Microcomposite by P/M route

- The best characteristics of P/M processed microcomposite can be achieved when the reinforcement is homogeneously distributed in the matrix

- It is possible when the matrix-to-reinforcement particle (MTRP) size ratio is close to or less than unity

- Mechanical Alloying (MA) – Nanostructured materials- To prevent reinforcement clusters or agglomerates on the matrix

especially in the case of small size reinforcement particles- MA produces uniform dispersion of the reinforcement particles in the

matrix- MA is one SPD process in which high strain is imparted on the material

and consequently the structural refinement occurs

1.0 Material, Process selection

5

1.0 Phenomenology of Nanostructured Formation by Mechanical Alloying (MA)

Hardened steel or WC

balls

High velocity of the ball

Fractured Powders

Material Transfer occurred

Fig.Schematic diagram of Mechanical Alloying 6

During MA processes, repeated fracturing, deforming, and cold-welding occurs due to the collision between the ball-to-powder or high impact on the powder.

3.0 Research Gap

1. Various researchers have successfully dispersed and alloyed, investigated and reported the diverse hard reinforcements such as graphite, SiC, Al2O3, TiC, VC, AlN, B4C, Si3N4, TiB2, AlB2 , Y2O3 and MgB2 on the aluminium-based MMCs through MA route

2. Use of TiO2 as reinforcement in aluminium alloys has received a meager concentration although it possesses high hardness and modulus with superior corrosion resistance and wear resistance

3. There is no work on cold workability / deformation behavior on nanocrystalline / nanocomposite under cold upsetting tests

7

3.0 Problem defined

Synthesis, characterization and workability behavior of nanocrystalline AA 6061 alloy reinforced with TiO2 prepared by mechanical alloying

8

3.0 Objectives1. To investigate the synthesis and characterization of AA

6061100-x – x wt.% TiO2 (x = 0, 2, 4, 6, 8, 10 and 12 wt.%) micro and nanocomposites powders prepared by blending (low-energy) and mechanical alloying (high-energy ball milling)

2. To study the effect of particle size-to-reinforcement ratio in terms of compressibility, green compressive strength and densification of both composites

3. To study the powder flow characteristics, compressibility and sinterability of both composites

4. To investigate the effect of microstructure, mechanical properties and the various strengthening mechanisms such as solid solution, grain size, precipitate, dislocation and dispersion strengthening during grain refinement of AA 6061-10wt.% TiO2 composite as an example

9

Contd..5. To study cold workability and instantaneous strain hardening

behavior during grain refinement of AA 6061-10wt.% TiO2 composite as an example.

6. To address the improvement of deformability/ductility of AA 6061–10 TiO2 nanocrystalline/nanocomposite via non-uniform bimodal/trimodal grain size distribution.

7. To study the microstructural evaluations of Trimodal AA 6061-TiO2 nanocomposite using different geometric characterization techniques.

8. To study the effect of CG content in AA 6061-TiO2 nanocomposite structure on cold workability and strain hardening behavior at room temperature.

9. To establish artificial intelligent systems using ANFIS for predicting the compressibility of AA 6061100-x – x wt.%TiO2 nanocomposites as an example

10

3.0 Project work plan

Material selection – Composite(AA 6061100-x – x wt.% TiO2)

Synthesize

MicrocompositeBlending

NanocompositeMA

1. Powder characterization2. Flow characteristics3. Compressibility behavior4. Green compressive

strength5. Sinterability behavior

1. Grain refinement study (AA 6061-10%TiO2) (Strengthening mechanisms (SMs))2. Effect of SMs on cold workability and

Inst. Strain hardening behavior (AA 6061-10 TiO2)

Improvement of Ductility / Deformability

Non-uniform Bimodal/Trimodal

distribution

Workability and Inst. Strain hardening behavior

(AA 6061 (nc & µc) TiO2 particles)

11

Modeling using ANFIS

4.0 Experimental procedure

12

Pre-inspection

13

Fig. The morphology of as-received powders: (a) Al and (c) TiO2,

XRD patterns of as-received powders: (b) Al and (d) TiO2

4.0 Pre-inspection

4.0 Synthesis of micro composites powders

Fig. Schematic diagram of Low energy horizontal ball milling for

micro composites14

http://upload.wikimedia.org/wikipedia/commons/c/c2/Ball_mill.gif

Fig. Schematic diagram of high-energy wet planetary ball milling principle

(Mechanical Alloying) for nano-composites15

4.0 Synthesis of nanocomposites powders by mechanical alloying (MA)

280 rpm

100 rpm

4.0 Experimental methods – sample preparation

16

Type of composite

Synthesis Method Matrix-Reinforcement

Type of study/Investigation

Micro-composite

Blending (Low-energy ball milling)-BPR 1:3, 36 rpm, 15 h, dry

AA 6060100-x – x wt.% TiO2 (x = 0, 2, 4, 6, 8, 10 and 12)

-Powder morphology evaluation-Flow characteristics of powders-Structural evaluation-Compressibility behavior (Cold uniaxial compaction, 125, 250, 375, 500, 625, 750, 875, 1000, 125, 1250 Mpa)

-Green mechanical strength-Sintering behavior (400, 475, 550 and 625°C)

Nano-composite

Mechanical Alloying (MA)(High-energy ball milling)- BPR 10:1, 280 rpm, Toluene, 40 h

17

Type of study Composite Milling time/Consolidation

Type of study/Investigation

Grain refinement and its formability

AA 6061-10 wt.% TiO2

-1, 5, 10, 20, 30 and 40 h- 350 Mpa, degassed, sintered at 848 K for 90 min

-Various strengthening mechanisms- Workability and strain hardening behavior

Type of study Composite Type of study/InvestigationTrimodaled composite and its formability

Nanostructured AA 6061-10 wt.% TiO2 composite powders mixed with 0, 5, 10, 15, 20, 25 and 30 CG matrix

-Trimodaled microstructural distribution- Workability and strain hardening behavior

4.0 Experimental Methods – Samples preparation

4.0 Cold uniaxial compaction and sintering furnace

18

Entry Exit

Schematic diagram of conventional cold uniaxial compaction die process (double

end compaction type)

Schematic diagram of mechanical pusher furnace

- Each sintered preform subjected to an incremental compressive loads of 5KN (0.5 tone) and the upsetting was carried out between two flat, mirror finished open dies on a hydraulic press of 50 tone capacity

-The deformation was carried out until the appearance of the first visible crack on the free surface

4.0 Cold upset forging test for workability behavior

20

4.0 Geometry Characterization Techniques

- X-ray diffraction (XRD)

- Scanning Electron Microscope (SEM)

- Transmission Electron Microscope (TEM)

- Differential thermal analysis (DTA)

21

5.0 Results and Discussion

5.1 Powder surface morphology evaluation

Purpose of Study:

-Using Scanning Electron Microscopy (SEM)

-Homogeneous distribution of reinforcement particles on the matrix

-Embedding of reinforcement particles on the matrix

-Presence of any agglomeration or clustering of reinforcement particles with the matrix

-Particle shape, particle size and its distribution

22

5.1 Powder morphology evaluation - Microcomposite

Fig. The morphology of powders after 15 h by low-energy dry ball milling:

(a) AA 6061-4%TiO2, (c) AA 6061-10%TiO2, (b) and (d) magnified view of (a) and (c) shows the uniform distribution of TiO2

particles on the matrix

23

5.1 Powder surface morphology evaluation – Function of milling time

Fig. Morphology of AA 6061-10% TiO2 composite powder as the function of milling time after (a) 01 h (inset on the upper left shows

the agglomeration of TiO2 particles on the matrix due to cold welding) (b) 05 h, particle flattening and fracturing (c) 10 h, welding

predominance (d) 20 h, equiaxed particle formation (fracturing dominance) (e) 40 h, equiaxed particles (steady state) (f) magnified

view of (e) shows the embedding of TiO2 particles on the matrix.24

5.1 Mapping and EDAX spectrum – AA 6061-10 TiO2 nanocomposite (40 h)

Fig. (a) EDAX mapping of AA 6061-10 wt.% TiO2 nanocomposite powder after 40 h MA, Red, Green and Blue

indicates Al, O and Ti elements respectively (b) The corresponding EDAX spectrum 25

5.1 Powder surface morphology evaluation - Function of reinforcement

Fig. The morphology of powders after 40 h milling: (a) AA 6061, (b) AA 6061-2% TiO2, (c) AA 6061-4% TiO2 and (d) AA

6061-6% TiO2.26

5.1 Powder surface morphology evaluation - Function of reinforcement

Fig. The morphology of powders after 40 h milling: (e) AA 6061-8% TiO2,

(f) AA 6061-10% TiO2, (g) AA 6061-12% TiO2 and (h) BSEI of magnified view of (g) shows the embedding of TiO2 particles

on the matrix

27

Fig. TEM image of AA 6061-12 wt.% TiO2 nanocomposite powder: (a) bright field image (b) dark field image

28

5.1 TiO2 Particle size measured from TEM

5.1 Particle / agglomerate size analysis – Micro and nanocomposite

Fig. Particle/agglomerate size distribution of AA 6061100-x-x wt.% TiO2 of micro and nanocomposite powders: (a) 0%,

(b) 4%, (c) 8% and (d) 12%.29

5.1 Particle / agglomerate size analysis – Function of milling time

Fig. Effect of milling time on the average particle size of AA 6061-10 wt.% TiO2 composite powders 30

5.2 Powder flow characteristics

- Knowledge about the flow characteristics of powders is very important for a successful product development

- Generally, the flow characteristics of powder are evaluated by poured bulk density or random loose packing (apparent density) – standard funnel method,

- Compressed bulk density or random dense packing (tap density) – tap tester

- True density – Pycnometer

- To study the cohesive nature of the powders

- To analysis the flow rate of the powders

- It is important to report the initial state of the powders being subjected to the compaction

Purpose of study:

31

5.2 Powder flow characteristics – Function of reinforcement

Fig. Apparent density, tap density and true density of AA 6061100-x – x wt.% TiO2 (x = 0, 2, 4, 6, 8, 10 and 12) for

micro and nanocomposite powders. 32


Fig. (a) Hausner ratio (b)cohesiveness of AA 6061100-x – x wt.% TiO2 (x = 0, 2, 4, 6, 8, 10 and 12) micro and

nanocomposite powders33

Fig. Flow rate of AA 6061100-x – x wt.% TiO2 (x = 0, 2, 4, 6, 8, 10 and 12) micro and nanocomposite powders

34


5.2 Powder flow characteristics – Function of milling time

35

Milling

condition

Apparent

density, g/cm3

Tap density,

g/cm3

True density,

g/cm3

Flow rate,

s/50g

00 h 1.2497±0.0081 1.4965±0.0734 2.5746±0.0569 0.6790±0.0251

01 h 1.2887±0.0032 1.5098±0.0023 2.2964±0.0012 0.6803±0.0046

05 h 1.2812±0.0025 1.4625±0.0068 1.8117±0.0023 0.6035±0.0017

10 h 1.2719±0.0031 1.4248±0.0035 1.9217±0.0030 0.5273±0.0027

20 h 1.2823±0.0025 1.3943±0.0045 2.1151±0.0058 0.4517±0.0014

30 h 1.2972±0.0039 1.3688±0.0055 2.2883±0.0019 0.4149±0.0023

40 h 1.3085±0.0050 1.3702±0.0012 2.5012±0.0475 0.4241±0.0231

Table . Basic characteristics of AA 6061 – 10 wt. % of TiO2

composite powder as function of milling time


Fig. Cohesiveness with function of milling time36

Fig. Schematic relation between the milling time, the morphology, and the apparent density of ductile–ductile

and ductile–brittle system powder prepared by high-energy milling

37


5.3 Structural Evaluation of Mechanically alloyed (MAed) powders

Purpose of study

38

- MA causes morphological and structural changes

- SPD of the powder particles during MA can lead to grain refining, variation in the crystallite size, accumulation of internal stress, density of dislocation and variation of the lattice parameter

- XRD, TEM, HR-TEM, EDS and differential thermal analyzer (DTA).

5.3 X-ray diffraction (XRD) analysis

Fig. XRD patterns of AA 6061 – 10 wt.% TiO2 composite powder after 0, 1, 5, 10, 20, 30 and 40 h milling. Inset shows the initial sharp diffraction peaks of Al getting

broadened and reduced in intensity39

XRD patterns as function of milling time


Fig. Variation of crystallite size and lattice strain for AA 6061 – 10wt.% TiO2 composite powder as a function of

milling time40

Crystallite size and lattice strain as function of milling time


Fig. Variation of dislocation density, r.m.s strain and volume fraction of TiO2 for AA 6061 – 10wt.% TiO2 composite

powder as a function of milling time41

Dislocation density and volume fraction of TiO2 as function of milling time


Fig. Variation of lattice parameter for AA 6061 – 10wt.% TiO2 composite powder as a function of milling time

42

Lattice parameter as function of milling time


Fig. XRD patterns of AA 6061100-x – x wt.% TiO2 (x = 0, 2, 4, 6, 8, 10 and 12%) nanocrystallite/nanocomposite powder after 40 h of high energy ball milling. Inset shows shift in Bragg’s

angle43

XRD patterns as function of reinforcement

Diffraction angle (2θ), deg.


Fig. XRD patterns of AA 6061100-x-x wt.% TiO2, x = 0, 4, 8, and 12%, composite powder after 40 h of high-energy ball

milling44

XRD patterns as function of reinforcement


Fig. Variation of crystallite size, lattice parameter and solid solution of TiO2 for AA 6061100-x – x wt.% TiO2 (x = 0, 2, 4, 6, 8, 10 and 12 wt.%) nanocomposite powder as a function of

reinforcement45

Structural changes as function of reinforcement

5.3 X-ray diffraction (XRD) patterns of Microcomposite

46

Inte

nsity

, a.u

.

Diffraction angle (2θ), deg

Fig. XRD patterns of AA 6061100-x – x wt.% TiO2 (x = 0, 2, 4, 6, 8, 10 and 12%) microcomposite powder after 15 h of low

energy ball milling

5.3 TEM Analysis of MAed Powders

47

TEM micrographs of as milled nanocomposite powders: (a) bright field image (BFI) of 0% TiO2, (b) SAD pattern of 0% TiO2, (c) EDAX analysis of 0% TiO2 (d) BFI of 4% TiO2, (e)

dark field image (DFI) of 4%TiO2 (inset shows the SAD), (f) EDAX analysis of 4% TiO2

5.3 TEM Analysis of MAed powders

48

TEM micrographs of as milled nanocomposite powders: (g) BFI of 8% TiO2, (h) DFI of 8% TiO2 (inset shows the SAD), (i)

EDAX analysis of 8% TiO2, (j) BFI of 12% TiO2, (k) DFI of 12% TiO2 (inset shows the SAD) and (l) EDAX analysis of

12% TiO2. Note: single arrow represents TiO2 particle

5.3 HR-TEM Analysis of AA 6061-10 wt.% TiO2 powders after 40 h MA

49

Fig. HR-TEM image of AA 6061 – 10 wt.% TiO2 nanocomposite:

(a) Lattice resolution image (b) the corresponding SAD

(b)

Fig. The DTA curve of AA 6061 and AA 6061 – 12 wt.% TiO2 nanocrystallite / nanocomposite powders prepared by 40 h

of mechanical alloying

5.3 Differential thermal analysis (DTA)

50

5.4 Compressibility behavior of micro and nanocomposite powder

To investigate the relationship between the powder surface morphology and the compressibility of low-energy (microcomposite, 15 h) and high-energy (nanocomposite, 40 h) ball milled powders

The Panelli and Filho compaction Eq.

(5.5)

Where, D is relative density, P compaction pressure, A and B are constants

Purpose of study

51

BPAD

11ln

5.4 Compressibility curves of microcomposite powders

52

Fig. Compressibility curves (upper side) and experimental data fitted by the Panelli and Filho equation (bottom side)

of AA 6061100-x – x wt.% TiO2 microcomposites powder, x = 0, 4, 8, and 12%

5.4 Compressibility curves of nanocomposite powders

53

Fig. Compressibility curves (upper side) and experimental data fitted by the Panelli and Filho equation (bottom side)

of AA 6061100-x – x wt.% TiO2 nanocomposites powder, x = 0, 4, 8, and 12%

5.4 Densification parameter of micro and nanocomposite powders

54

Fig. Parameter A obtained from Eq. (5.5) as function of reinforcement for micro and nanocomposites powder

5.4 Compressibility curves as function of milling time

55

Fig. Compressibility curves (upper side) and experimental data fitted by the Panelli and Filho equation (bottom side) of AA 6061 – 10wt.% TiO2 composite powder with function of milling time

5.4 Densification parameter as function of milling time

56

Fig. Parameter A obtained from Eq. (5.5) as function of milling time

5.5 Evaluation of compaction equations

- To develop a linear and non-linear relationship between pressure and relative density

- To predict the required pressure in obtaining a certain level of density

Purpose of study:

57

• Linear compaction equations:

- The use and derivation of compaction equations have played an important role for evaluation of compaction behavior

- A compaction equation relates some measure of the state of consolidation of a powder, such as, porosity, relative density, or void ratio, with a function of the compaction pressure

• Non-linear compaction equations:

- To evaluate the role of particle rearrangement and plastic deformation of materials during compactions exactly, nonlinear compaction equations are of interest to engineers, physicists and mathematicians as most physical systems (here compaction) are inherently nonlinear in nature

5.5 Evaluation of Compaction equations

1) Balshin :

Linear Equations:

58

11 ln1 BPAD

2) Heckel : 221

1ln BPAD

3) Ge :

33 log1

1lnlog BPAD

4) Panelli and Filho :

4411ln BPAD

5) Kawakita : 5

5

0

BPA

DDD

6) Shapiro : 5.0

01ln1ln bPkPDD

Non-Linear Equations: 7) Cooper and Eaton:

PA

BPA

BDDD 7

76

60

0 exp1

8) Zwan and Siskens :

PA

BDDD 8

80

0 exp1

Table . Crystallite size, particle size, apparent density, tap density, flow rate, theoretical density and relative apparent density of AA 6061100-x – x wt.% TiO2 (x = 0, 2, 4, 6, 8, 10 and

12 wt.%) nanocomposite powder

59

% of nano

titania on NC matrix

Crystallite size of the NC matrix,

nm

Mean particle size,

m

Apparent

density, g/cm3

Tap densit

y, g/cm3

Flow rate, s/50g

Theoretical

density, g/cm3

Relative

apparent

density (D0)

0 652.50 131.201.3606

01.438

500.269

102.70000

0.50393

2 614.20 122.301.3512

11.428

560.283

002.72280

0.49626

4 585.00 104.801.3483

01.420

000.297

802.74560

0.49108

6 553.50 83.501.3324

61.394

670.324

112.76840

0.48131

8 504.60 67.751.3198

01.364

500.354

402.79120

0.47284

10 484.00 60.451.3084

81.352

150.423

562.81400

0.46499

12 462.00 56.461.2985

01.340

200.493

802.83680

0.45773

Table. Comparison of linear and non-linear compaction equations of AA 6061100-x - x wt.% TiO2 nanocomposite

powder after 40h MA, x = 0, 2, 4, 6, 8, 10 and 12%.

60

S.No PowderEq. (1) Eq. (2) Eq. (3)

A1 B1 R2A2

(x10-2)B2 R2 A3 B3 R2

1 AA 6061 -0.0672 1.5044 0.9687 0.1331 1.8875 0.9522 0.2979 -0.3772 0.9916

2AA 6061 + 2%

TiO2-0.0735 1.5527 0.9717 0.1297 1.8220 0.9387 0.3025 -0.4054 0.9901

3AA 6061 + 4%

TiO2-0.0817 1.6137 0.9702 0.1333 1.7110 0.9492 0.3176 -0.4612 0.9823

4AA 6061 + 6%

TiO2-0.0860 1.6492 0.9739 0.1295 1.6527 0.9586 0.3160 -0.4711 0.9849

5AA 6061 + 8%

TiO2-0.0902 1.6837 0.9755 0.1230 1.6070 0.9600 0.3122 -0.4749 0.9859

6AA 6061 + 10% TiO2

-0.1005 1.7613 0.9779 0.1294 1.4843 0.9688 0.3214 -0.5176 0.9910

7AA 6061 + 12% TiO2

-0.1117 1.8460 0.9766 0.1200 1.4512 0.9568 0.3314 -0.5621 0.9934

Table 3 –Contd..

61

Eq. (4) Eq. (5) Eq. (6) Eq. (8)

A4 B4 R2 A5 B5 R2k

(x10-3)b R2 A8 B8 R2

0.0700 1.0601 0.9894 62.7904 2.0423 0.9800 -0.5941 0.10177 0.9559 0.2636 188.679 0.9954

0.0681 1.0119 0.9855 65.5389 2.0163 0.9637 -0.5658 0.09745 0.9642 0.2593 234.741 0.9970

0.0698 0.8849 0.9875 70.2234 1.9998 0.9284 -0.3633 0.08874 0.9572 0.2672 295.858 0.9913

0.0676 0.8564 0.9919 70.4623 1.9676 0.9317 -0.3384 0.08527 0.9723 0.2704 294.985 0.9931

0.0646 0.8463 0.9921 71.0989 1.9422 0.9351 -0.3426 0.08283 0.9726 0.2743 291.545 0.9937

0.0636 0.7772 0.9934 78.7934 1.9124 0.9582 -0.2630 0.07721 0.9819 0.3033 261.096 0.9974

0.0628 0.7093 0.9931 87.5172 1.8848 0.9730 -0.1694 0.07219 0.9764 0.3367 236.406 0.9984

Fig.. Compressibility curves of AA 6061 – x wt.% TiO2 (x = 0, 2, 4, 6, 8, 10 and 12) nanocomposite powders as a function

of compaction pressure at various TiO2 percentages 62

(i)Particle rearrangement (PR)(ii)Plastic deformation (PD)

PR<375 MpaBoth-375 to 1000 MpaPD>1000Mpa

Fig. Relative density versus compaction pressure of AA 6061 – 12 wt. % TiO2 nanocomposite powder. The different line types show the fitting of experimental data with different

compaction equations.63

Fig. Relative density Vs compaction pressure well fitted to the Zwan and Siskens Eq. (5.13) (non-linear) for AA 6061100-x – x wt.% TiO2

nanocomposite powder after 40h MA64

Fig. SEM/SEI micrographs show the fracture surfaces of AA 6061-12 wt.% TiO2 nanocomposite powder compacted at: (a) 125 MPa (particle rearrangement stage) and (b) 1500 MPa

(plastic deformation stage)

65

5.5 Fracture surfaces of post-compacts

Fig. Effect of the percentage of reinforcement on the rate of plastic deformation (ap) and the corresponding magnitude of

pressure at the start of plastic deformation (kp) during compaction of AA 6061100-x – x wt.% TiO2 nanocomposite powders. (using non-linear Zwan and Siskens Eq. (5.13))

66

Pk

aDDD p

p exp1 0

0

5.6 Green Mechanical Strength and Sintering Behavior

67

Purpose of study:

Best mechanical properties obtained by homogeneous distribution of reinforcement

It is possible when Matrix-to-particle size ratio (MTRPR) is close or less than 1

If MTRPR >1, Clustering of reinforcement takes place that detoriates mechanical properties

To investigate the effect of MTRPR, powder morphological changes such as size and shape, percentage of reinforcement and grain refinement on green compressive strength, hardness of sintered micro and nanocomposite and sintered densification behavior of both composite.

5.6 Microstructural evaluation of post-compacts as function of reinforcementMicrocomosite

2 % TiO2

6% TiO2

12 % TiO2

68

Nanocomosite

2 % TiO2

6% TiO2

12 % TiO2

5.6 Microstructural evaluation of post-compacts as function of reinforcement

69

AA 6061-10TiO2

01 h

05 h

10 h

5.6 Microstructural evaluation of post-compacts as function of milling time

70

71

AA 6061-10TiO2

40 h

5.6 Microstructural evaluation of post-compacts as function of milling time

Fig. SEM/BSEI of AA 6061-10 wt.% TiO2 post-compacts compacted at 500 MPa. Left side (a), (c), (e) and (g) show

after 1, 5, 10 and 40 h. Right side (b), (d), (f) and (g) show magnified view of corresponding post compacts.

Note: single arrow represents TiO2 clusters; double arrow represents distribution of TiO2 particles

72

5.6 Mapping of AA 6061-10 TiO2 – 05 h, post-compact, 500 MPaMixed Al Kα

5 mTi Kα O Kα

73

5.6 Mapping of AA 6061-10 TiO2 – 40 h, post-compact, 500 MPaMixed Al Kα

5 mTi Kα O Kα

5.6 Green compressive strength as function of reinforcement and milling time

74

MTRPR

Micro Nano

0 -- --

2 49.32 1025

4 48.84 882

6 47.82 706

8 46.75 571

10 45.48 504

12 43.89 470

5.6 Sintering behavior of micro and nanocomposite

75

Fig. Densification of AA 6061100-x-x wt. % of TiO2, x = 0,4, 8 and 12 wt.%: (a) microcomposite and (b) nanocomposites

5.6 Sintering behavior of micro and nanocomposite

76

Fig. Contour graph of sintering behavior in terms of % theoretical density: (a) microcomposite and (b) nanocomposite

77

Fig. XRD patterns of AA 6061100-x – x wt.% TiO2, x = 0, 4, 8 and 12 wt.% nanocomposite sintered at 550°C for 2 h

5.6 XRD patterns of Nanocomposite sintered at 550 °C

5.6 Crystallite size as function of reinforcement after sintering at 550°C

78Fig. Crystallite size as function of reinforcement in as-milled and as-sintered at 550°C

condition

5.6 TEM analysis of AA 6061-12 wt.% TiO2 nanocomposite sintered at 550°C

79

Fig. (a) TEM bright field image of AA 6061-12 wt.% TiO2 nanocomposite sintered at 550 °C (b) the corresponding SAD ring pattern indicating UFG

nature of matrix

5.6 Vickers Hardness – Function of sintering temperature

80

5.6 Vickers Hardness – Function of sintering temperature

81

Fig. Effect of composition on Vickers hardness of AA 6061100-x – x wt.% TiO2 (x = 0, 2, 4, 6, 8, 10 and 12) bulk

micro and nanocomposites (sintered at 625°C)

5.7 Grain refinement and its formability

Purpose of study

To investigate the dominant strengthening mechanisms

Sample – AA 6061-10 TiO2 (1h, 5h, 10h 20h, 30h and 40 h)

To study the effect of strengthening mechanisms on the cold workability during grain refinement and at its strain hardening behavior

82

5.7 Grain refinement study – XRD analysis

Fig. XRD patterns of sintered AA 6061-10 wt.% TiO2 composites as function of milling time 83

5.7 Phase evaluation using XRD analysis of AA 6061 – 10 TiO2 sintered composite

Milling time, h

Phase formation after sintering at 848K for 90 min (crystallite size, nm)

1 -Al (1602) + TiO2 (45) + Al2O3 (38)

5 -Al (792) + TiO2 (44) + Al2O3 (38)

10 -Al (545) + TiO2 (41) + Al2O3 (38)

20 -Al (374) + TiO2 (40) + Al2O3 (38)

30 -Al (304) + TiO2 (40) + Al2O3 (38)

40 -Al (292) + TiO2 (39) + Al2O3 (38)

- Crystallite size of α-Al phase after sintering showed a decreasing value from very CG to UFG with milling time due to grain refinement

- The increase in milling time pinned the grain growth during sintering

84

Fig. Bright field image of as-sintered AA 6061-10 wt.% TiO2 composite after 40 h MA showing the nanometer-size TiO2

particles embedded in the α-Al matrix. Inset shows the corresponding SAD ring pattern indicating ultra fine

crystalline nature

5.7 TEM analysis of AA 6061 – 10 TiO2 40 h sintered composite

(848 K, 90 min, N2 atm.)

85

Fig. TEM bright-field image showing the distribution of TiO2 particles within the grain interior as well as along the

grain boundaries of as-sintered AA 6061-10 wt.% TiO2 composite after 40 h MA


(848 K, 90 min, N2 atm.)

86

Fig. TEM dark-field image showing a nearly equiaxed TiO2 particle in an AA 6061-10 wt.% TiO2 sintered composite.

Inset of upper left showing the SAD pattern in [1 0 1] zone axis. Inset of bottom right showing the corresponding EDAX


(848 K, 90 min, N2 atm)

87

Fig. SEM/BSEI of AA 6061-10 wt.% TiO2 sintered composite: Left side (a), (c) and (e) shows after 1 h, 5 h and 40 h. Right side (b), (d) and (f) shows

magnified view of corresponding composites. Note: single arrow represents TiO2 clusters, double arrow represents distribution of TiO2 particles and

rectangle represents oxide particles

5.7 Microstructure analysis of sintered

samples

88

01 h

05 h

40 h

Fig. Optical microstructure of AA 6061-10 wt.% TiO2 sintered sample after milling: (a) 1 h, (b) 5 h, (c) 10 h, (d) 20 h, (e) 30 h and (f) 40 h.

Note: single arrow represents TiO2 clusters89

(a) (b)

(c) (d)

(e) (f)

100 m 100 m

100 m100 m

100 m100 m

5.7 Microstructure analysis of sintered

samples

5.7 Grain refinement study – Mechanical properties

Table. Density, volume fraction of Al2O3 (VAl2O3), TiO2 (VTiO2) and mechanical properties of sintered preform

90

Milling

time, h

Theoretical

density, %

Calculated

Al2O3

Calculated

TiO2

Hardness

(Hv1.0),

Mpa

Empirical

yield stress

(y), Mpa

Empirical

modulus (E),

GPa

01 92.9232 0.03936 0.07283 245.3680 81.7893 80.8454

05 89.5318 0.04715 0.07472 520.3698 173.4566 81.8946

10 86.1471 0.04871 0.07591 774.3698 258.1233 82.2444

20 83.0671 0.05167 0.07751 846.3298 282.1099 82.7906

30 81.7202 0.05221 0.07625 940.3690 313.4563 82.7551

40 81.9371 0.05429 0.07818 1010.3570 336.7857 83.1890

5.7 Strengthening Mechanisms on overall strength

91

Table. Calculated contribution of solid solution strengthening (σss), Orowan strengthening (σdisper1), grain size strengthening (σgs), dislocation strengthening (σdis) and dispersion strengthening

(σdisper2) to the empirical yield strength (σy) of sintered AA 6061-10 wt.% TiO2 composites

5.7 Grain refinement – Cold workability behavior Cold workability behavior

- It is the ability of a material to endure the induced internal stresses of forming former to the occurrence of splitting of material (i.e. a measure of the extent of deformation prior to fracture)

92

93

5.7 Grain refinement - Cold workability behavior

fz h

h0ln1) True axial strain 2) True hoop strain

2

0

22

32

ln21

DDD CB

3) True effective strain 21

22

222 )1(

3)2(422

)2(32

R

Rz

zzeff

4) True axial stress areasurfacecontactload

z 5) True hoop stress zRRR

22

2

222

6) True hydrostatic stress 3)2(

zm

7) True effective stress 21

2

2222

12)2(2

RR zz

eff

8) Formability stress indexeff

m

3

9) Instantaneous Poisson’s ratioz

i

10) Instantaneous strain hardening index

1

1

)()(

ln

)()(

ln

ieff

ieff

ieff

ieff

in

Fig. Variation of true effective stress with true axial strain as a function of milling time for AA 6061-10 wt.%

TiO2 sintered composites

5.7 True effective stress Vs True effective strain

94

Dislocation pile up, decrease the diff. of flow resistance

Fig. Variation of true hydrostatic stress with true effective strain as a function of milling time for AA 6061-

10 wt.% TiO2 sintered composites

5.7 True hydrostatic stress Vs True effective strain

95

Specific surface areaInterparticle friction

effects

Fig. Variation of formability stress index with true effective strain as a function of milling time for AA 6061-10 wt.%

TiO2 sintered composite96

5.7 Formability stress index Vs True effective strain

Fig. Variation of instantaneous Poisson's ratio with true effective strain as a function of milling time for AA 6061-10 wt.% TiO2 sintered composites

97

5.7 Inst. Poisson ratio Vs True effective strain

Fig. Variation of instantaneous strain hardening index with true effective strain as a function of milling time for AA

6061-10 wt.% TiO2 sintered composites

5.7 Inst. Strain hardening behavior Vs True effective strain

98

Fig. Variation of fracture limit strain and percentage of cold work as a function of milling time for AA 6061-10 wt.%

TiO2 sintered composites

5.7 Fracture limit strain and percent cold workability

99

Fig. 3D microstructure of AA 6061-10 wt.% TiO2 composite after cold deformation in perpendicular to axial

(Top), hoop (Front) and radial (Right) – magnification 200x: (a) 5 h and (b) 40 h 100

(a) (b)

5.8 Trimodaled nanocomposite and its workability

- To restore the ductility of nanocomposite while maintaining strength and toughness

- Methods: (1) Bimodal – for NC alloy (2) Trimodal – for

nanocomposite (3) Annealing – this promotes grain growth

Purpose of study

101

Fig. Incorporating coarse-grains to improve the ductility of nanocrystalline materials by consolidation of blended coarse grains powders: (a) before upsetting and (b) after upsetting

5.8 Optical Microstructures of Trimodaled composite

102

Fig. Trimodal microstructures of as-sintered AA 6061-TiO2 composites containing x wt.% CG matrix: (a) x = 0% , (b) x

=10% , (c) x = 20% and (d) x = 30% . The grey regions represent UFG matrix reinforced with nano Titania, the

bright regions represent CG matrix.

5.8 HR-SEM - BSEI of Trimodaled composites

103

0% CG

10% CG

104

20% CG

30% CG

5.8 TEM – Bright field image of 0% CG composites

105

Fig. Bright field image of 0% CG AA 6061-TiO2 composite showing the nano-sized titania particles embedded in the -Al matrix. Inset at upper left shows the corresponding SAD

ring pattern indicating UFG nature.

5.8 TEM – Dark field image of 0% CG composites

106

Fig. TEM dark-field image showing nearly equiaxed titania particles in 0%CG AA 6061-TiO2 composite. Inset at bottom

left showing the corresponding EDAX.


107Fig. (a) Bright field image of 15% CG AA 6061-TiO2

trimodaled composite


108Fig. (b) magnified view showing CG band region in 15% CG

trimodaled sample

(a)5.8 XRD study of Trimodaled composites

109Fig. The XRD patterns of trimodal AA 6061-TiO2 composite

with 0, 15 and 30 wt.% CG content. (a) As-sintered

5.8 Workability study on Trimodaled nanocomposite Purpose of study - Various authors have studied the mechanical behavior of

nanostructured materials in terms of simple Tensile and Compressive tests

- In fact, the uniaxial tensile test would not sustain a uniform tensile deformation at ambient temperature for more than a couple of percent of plastic strain, especially in refined grain materials.

- Hence, compression tests (like, here, cold-upsetting) are needed to provide a direct evaluation of the deformation behavior as the function of true effective strain because the compressive behavior is not strongly influenced by superfluous factors such as surface or internal blemish

- However, no detailed investigation has yet been conducted to examine the cold workability and strain hardening behavior of trimodal AA 6061-TiO2 nanocomposite

110

(a)

111Fig. The XRD patterns of trimodal AA 6061-TiO2 composite with 0, 15 and 30 wt.% CG content. (a) As-sintered (b) As-

deformed

(b)

112Fig. The XRD patterns of trimodal AA 6061-TiO2 composite with 0, 15 and 30 wt.% CG content. (a) As-sintered (b) As-

deformed

113

Fig. Initial and final diffraction peaks of -Al at (1 1 1) plane and TiO2 at (1 0 1) plane for 0% and 30% CG

composite in as-sintered and as-deformed condition.

Fig. Variation of true effective stress with true effective strain of trimodal AA 6061-TiO2 composites with the

function of wt.% CG content 114

• Nanocomposite possesses high strength bcoz of grain refinement, solute atoms of minor matrix elements and pinning effect of hard titania• 0%CG – poor strain hardening but IUCS of 3 times < conv. Al

•CG- helps to arrest the crack propagation – retards the plastic instability

•15%CG-High IUCS bcoz densification, non-colascence and effective load transfer

•30%CG possesses high toughness of 7 times higher than 0% CG

Fig. Variation of true hydrostatic stress with true effective strain with true effective strain, as a function of CG content

of trimodal AA 6061-TiO2 composite 115

• Porosity level•Interparticle friction effect during compaction

Fig. Variation of formability stress index with true effective strain with true effective strain, as a function of CG content

of trimodal AA 6061-TiO2 composite 116

• Max 0.34 for 0% CG• Max 0.47 for 30% CG

• increases steadily with CG content due to soft parent phase

Fig. Variation of instantaneous Poisson’s ratio with true effective strain with true effective strain, as a function of CG

content of trimodal AA 6061-TiO2 composite 117

•PD capacity•Plastic strain levels•0.14 to 0.24 for 0% CG•0.05 to 0.42 for 30% CG

Fig. Variation of instantaneous strain hardening index with true effective strain with true effective strain, as a function

of CG content of trimodal AA 6061-TiO2 composite 118

0%5% 10%

15%20%

25%30%

Fig. Variation of fracture limit strain, percentage of cold work and change in dislocation densities as the function of

CG content in AA 6061-TiO2 nanocomposite119

•%CW for 30%CG 6 times >0%CG

120

Table . Room temperature mechanical properties of present work and others for comparison.

Material MicrostructureUltimate strength (MPa)

Strain-to-failure

(%)References

MA of 0% CG AA 6061-TiO2 composite

Bimodal 870ICU 2.6ICU

Present work


Trimodal 884ICU 3.3ICU











CM of 0% CG Al-7.5 Mg alloy Unimodal 847T 1.4T

[Hayes et al, 2001]CM of 15% CG Al-7.5 Mg alloy Bimodal 778T 2.4T

CM of 30% CG Al-7.5 Mg alloy Bimodal 734T 5.4T

Conventional Al Unimodal 305ICU 35.5ICU [Narayanasamy et al, 2009]Conventional Al 5083 Unimodal 281T 16.0T [Hayes et al, 2001 ]CM of 50% CG AA 5083-B4C composite

Trimodal 1070C 0.8C [Ye et al, 2005]*ICU-Incremental cold upsetting behavior, T-Tensile behavior, C-Compressive behavior

121

Table . Room temperature mechanical properties of present work and others for comparison.

% of CG

matrix

Theoretical

density, (g/cm3)

Sintered

density (g/cm3)

Deformed

density

% of increased density after

deformation

As-sintere

d fractio

nal porosit

y

As-deform

ed fractio

nal porosit

y

True effective toughness (MPa)

Strain hardeni

ng toughness index

0 2.814 2.4231 2.4366 0.5574 0.1389 0.1341 55.2362 0.00985 2.8083 2.4207 2.4390 0.7540 0.1380 0.1315 77.3373 0.0124

10 2.8026 2.4189 2.4441 1.0427 0.1369 0.1279 93.4414 0.0153

15 2.7969 2.4293 2.4608 1.2958 0.1314 0.1201118.167

7 0.0195

20 2.7912 2.4311 2.4730 1.7219 0.1290 0.1140152.685

1 0.0252

25 2.7855 2.4311 2.4825 2.1123 0.1272 0.1087212.390

9 0.0349

30 2.7798 2.4376 2.5052 2.7752 0.1231 0.0987385.589

1 0.0501

5.9 Modeling of compaction behavior using Adaptive Neuro Fuzzy Inference

System (ANFIS)Purpose of study:

122

Takagi and Sugeno proposed the following general fuzzy rule:

),..........(

),........,(:)(

22110

2211

plp

llll

lpp

lll

xcxcxccYYTHEN

FisxandFisxandFisxIFRlRule

- The current P/M based industries require expert systems by which the properties of materials and process related information which can be stored easily.

- The stored information in expert systems can be used during the design stage to select the material and verify the properties attainable through the process before the part designs are finalized.

- Hence, here ANFIS was established to predict the compressibility behavior of the fabricated composite powder for Industrial Application

123Fig. The ANFIS architecture for predicting relative density

of the post-compacts

84 – Total data sets49-Training35-Testing18-Validation (New)

124

Linguistics variables for Percentage of reinforcement

(X1)LowestLowerLow

MediumHigh

HigherHighest

Linguistics variables for compaction pressure (X2)

LowestLowerLow

MediumHigh

HigherHighest

Linguistic variable used in ANFIS architecture

Linguistics variables for relative density (Y)

Extreme LowLowestLowerLow

Almost LowUnder Medium

PremediumMedium

Over MediumUpper Medium

Almost HighHigh

HigherHighest

Extreme High

125Fig. Initial and final triangular MF of percentage of nano

titania content in NC matrix, wt.%

126Fig. Initial and final triangular membership function of

compaction pressure (P), MPa

127Fig. Comparison of measured and predicted relative density (D)

(upper side), and scatter diagram of measured and predicted relative density (D) (bottom side) for testing data

128

Table Comparison of relative density measured, predicted by ANFIS and MRA for testing data on the compaction of AA 6061100-x - x wt.% TiO2

nanocomposite powder, x = 0, 2, 4, 6, 8, 10 and 12.S.No

Percentage of nano titania in the NC matrix, wt.%

Compaction pressure (P), Mpa

Relative density (D)

MeasuredANFIS MRA

Predicted Error, % Predicted Error, %

1 0 375 0.90831 0.91854 -1.12703 0.88734 2.308202 0 625 0.93804 0.93512 0.31181 0.91541 2.413463 0 875 0.95812 0.95755 0.05945 0.94347 1.528684 0 1125 0.96882 0.97022 -0.14535 0.97154 -0.280735 0 1375 0.97259 0.97217 0.04274 0.99960 -2.777176 2 375 0.89612 0.89807 -0.21679 0.88010 1.788397 2 625 0.93579 0.93512 0.07157 0.90816 2.952328 2 875 0.95479 0.95462 0.01728 0.93623 1.943909 2 1125 0.96491 0.96535 -0.04492 0.96429 0.0645610 2 1375 0.96880 0.96827 0.05449 0.99236 -2.4313711 4 375 0.88255 0.87564 0.78270 0.87285 1.0982712 4 625 0.93050 0.93317 -0.28696 0.90092 3.1790413 4 875 0.95122 0.95170 -0.04969 0.92898 2.3381014 4 1125 0.96101 0.96047 0.05559 0.95705 0.4119315 4 1375 0.96737 0.96730 0.00700 0.98511 -1.8345716 6 375 0.87571 0.86881 0.78808 0.86561 1.1538217 6 625 0.92420 0.92829 -0.44299 0.89368 3.3028518 6 875 0.94431 0.94390 0.04437 0.92174 2.3906119 6 1125 0.95611 0.95560 0.05392 0.94980 0.6597420 6 1375 0.96453 0.96437 0.01650 0.97787 -1.3827821 8 375 0.86885 0.86101 0.90226 0.85837 1.2067422 8 625 0.91786 0.92244 -0.49992 0.88643 3.4235723 8 875 0.93724 0.93707 0.01790 0.91450 2.4264324 8 1125 0.95114 0.95072 0.04389 0.94256 0.9018425 8 1375 0.96016 0.96047 -0.03269 0.97063 -1.0901626 10 375 0.85912 0.85614 0.34761 0.85112 0.9311727 10 625 0.90874 0.91074 -0.22010 0.87919 3.2522028 10 875 0.93137 0.93219 -0.08897 0.90725 2.5890029 10 1125 0.94611 0.94487 0.13121 0.93532 1.1409530 10 1375 0.95575 0.95560 0.01590 0.96338 -0.7986931 12 375 0.84717 0.85029 -0.36756 0.84388 0.3886432 12 625 0.89989 0.89904 0.09411 0.87194 3.1052133 12 875 0.92509 0.92732 -0.24066 0.90001 2.7114434 12 1125 0.94097 0.94000 0.10353 0.92807 1.3704435 12 1375 0.95110 0.95170 -0.06248 0.95614 -0.52956

Maximum percentage of error 0.90226 3.42357Minimum percentage of error -1.12703 -2.77717

Mean percentage of error 0.00388 1.13876Correlation coefficient 0.99578 0.93934

129

Fig.. Comparison of measured and predicted relative density (D) (upper side), and scatter diagram of measured and predicted

relative density (D) (bottom side) for validation data

130

Comparison of relative density measured, predicted by ANFIS and MRA for validation / checking data on the compaction of AA 6061100-x - x wt.% TiO2

nanocomposite powder, x = 3, 7 and 11

S.NoPercentage of nano

titania in the NC matrix, wt.%

Compaction pressure (P),

Mpa

Relative density (D)

Measured

ANFIS MRA

Predicted Error, % Predicted Error, %

1 3 300 0.87881 0.87564 0.36098 0.86806 1.22382

2 3 500 0.91932 0.91952 -0.02142 0.89051 3.13421

3 3 700 0.94212 0.94097 0.12153 0.91296 3.09470

4 3 900 0.95567 0.95462 0.10921 0.93541 2.11936

5 3 1100 0.96355 0.96242 0.11748 0.95786 0.59066

6 3 1300 0.96678 0.96632 0.04710 0.98032 -1.40019

7 7 300 0.85223 0.85126 0.11382 0.85357 -0.15697

8 7 500 0.90745 0.90782 -0.04094 0.87602 3.46297

9 7 700 0.93200 0.93024 0.18851 0.89847 3.59748

10 7 900 0.94211 0.94195 0.01758 0.92092 2.24884

11 7 1100 0.95156 0.95170 -0.01411 0.94338 0.86027

12 7 1300 0.96237 0.96145 0.09540 0.96583 -0.35980

13 11 300 0.83989 0.84054 -0.07735 0.83908 0.09565

14 11 500 0.88122 0.88734 -0.69408 0.86153 2.23434

15 11 700 0.91112 0.91464 -0.38628 0.88399 2.97846

16 11 900 0.92755 0.93024 -0.29001 0.90644 2.27661

17 11 1100 0.93720 0.94000 -0.29829 0.92889 0.88672

18 11 1300 0.95189 0.95267 -0.08214 0.95134 0.05762

Maximum percentage of error 0.36098 3.59748

Minimum percentage of error -0.69408 -1.40019

Mean percentage of error -0.04072 1.49693

Correlation coefficient 0.99836 0.94186

Fig. Morphology of AA 6061 reinforced with: (a) 3 wt.% TiO2, and (b) 7 wt.% TiO2

131

(a) (b)

Fig. Variation of relative density as the function of percentage of nano titania content in the NC matrix and

compaction pressure for AA 6061100-x – x wt.% TiO2 nanocomposite powders predicted by ANFIS model.

132

133

6.0 Conclusions New nanocomposite of AA 6061100-x – x wt.% TiO2 successfully synthesized and investigated

Crystallite size of the matrix decreased steadily with TiO2 due to more fragmentation led structural refinement

TEM microstructures of as-milled powder samples showed the matrix grain sizes ranging from 45-75 nm (depending of reinforcement) which were coherent with XRD results

Matrix particle size decreased drastically with TiO2 due to its also acted as milling agent

40 h led to extremely refined microstructure with the crystallite size of about 48 nm in as-milled condition

The irregular flake like shaped powder morphology (0 h) was changed to regular and equiaxed with almost spherical shaped powder morphology (40 h) with milling time

The evolution of powder flow characteristics in terms of apparent, tap and true density, cohesiveness in terms of Hausner ratio and Kawakita and Lüdde plot, and flow rate variations with milling time were obviously due to morphological and microstructural changes imposed on the composite powder particles by the grinding medium

134

6.0 ConclusionsFurther, the apparent and tap density decreased with percentage of reinforcement in both the composite. This was attributed to the internal friction and or anelasticity

The flow rate of the nanocomposite powder particles possessed higher value than the corresponding microcomposite powder particles due to equiaxed with almost spherical shaped and refined powder morphology.

The compressibility in terms of parameter A decreased steadily in microcomposite

The compressibility in terms of parameter A decreased slightly

Among the developed compaction equations, the non-linear Zwan and Sizkens equation exhibited/produced excellent relationship between the relative denisity (D) and compaction pressure (P)

As the grains decreased from very CG to UFG of sintered MAed composite, the workability curves in terms of true effective stress increased steeply from 405 MPa (1 h) to 808 MPa (40 h) with sharp decreasing of true effective strain from 25 % (5 h) to 1.7 % (40 h).

It was found from formability behavior of grain refinement samples that the grain size and dislocation strengthening mechanisms had much influence on the formability

135

6.0 Conclusions The study of trimodaled composite and its formability behavior demonstrated the occurrence of simultaneous improvements in the compressive ductility and toughness of AA 6061-TiO2 nanocomposite by introducing different weight percentage of CG matrix in the nanocomposite

This was attributed to the addition of CG soft parent phase in the nanostructured phase which enhanced the dislocation activity. The 15% CG trimodaled composite exhibited high strength (935 MPa) during cold-upsetting and it produced incremental compressive ductility of 4.6 % of strain-to-failure.

the 30% CG trimodaled composite produced higher strain-to-failure value of 16.2% which was around 6 times higher than 0% CG trimodaled composite

The developed non-linear model using ANFIS approach can be used to predict the compaction behavior of the fabricated nanocomposite accurately

136

6.0 Scope for future work Study of mechanical behavior in terms of tensile strength, ductility (strain-to-failure) and Young modulus of the developed nanocomposite to be consolidated for getting cent percent densification by hot pressing followed by hot extrusion or SPS followed by hot extrusion Hot deformation / hot forging behavior of the developed nanocomposite with varying temperatures and strain rate Development of processing map for the developed nanocomposite to investigate the flow stress behavior by which one can identify the safe region and unsafe region while deforming the nanocomposite Development of processing map for the developed nanocomposite under porous condition to investigate the compressibility, mechanical properties and workability behavior by varying: (i) percentage of reinforcement, (ii) TiO2 particle size starting from micron-to-submicron-to-nano (iii) charge ratio (e.g. 10:1, 20:1 and 30:1), (iv) longer milling time (e.g. 20 h, 40 h, 60 h and 80 h) (iv) operating temperature and (v) strain rate and (vi) aspect ratio Study of tribological and corrosive behavior of the developed nanocomposite Study of machinability behavior either using simple drilling or turning operation for the developed nanocomposite Establishment of artificial neural network model (ANN), fuzzy logic model and hybrid model to predict the compaction and mechanical behavior (mechanical properties and workability).

7.0 Publications 1. Sivasankaran, S., Sivaprasad, K. R. Narayanasamy and V. K.

Iyer (2010) An investigation on flowability and compressibility of AA 6061100-x - x wt.% TiO2 micro and nanocomposite powder prepared by blending and mechanical alloying. Powder Technol., 201(1), 70-82. [20TH ARTICLE AMONG TOP 25 HOTTEST ARTICLES in Powder Technology from May 2010 to July 2010]

2. Sivasankaran, S., Sivaprasad, K. R. Narayanasamy and V. K. Iyer (2010) Synthesis, structure and sinterability of 6061 AA100−x–x wt.% TiO2 composites prepared by high-energy ball milling. J. Alloys Compd., 491(1-2), 712-721.

3. Sivasankaran, S., Sivaprasad, K. R. Narayanasamy and V. K. Iyer (2010) Effect of strengthening mechanisms on cold workability and instantaneous strain hardening behavior during grain refinement of AA 6061-10 wt.% TiO2 composite prepared by mechanical alloying, J. Alloys Compd., 507(1), 236-244.

4. Sivasankaran, S., Sivaprasad, K. R. Narayanasamy and V. K. Iyer (2011) Evaluation of compaction equations and prediction using adaptive neuro-fuzzy inference system on compressibility behavior of AA 6061100-x – x wt.% TiO2 nanocomposites prepared by mechanical alloying. Powder Technol.,209, 124-137.

INTERNATIONAL JOURNALS

137

Publications 5. Sivasankaran, S. K. Sivaprasad and R. Narayanasamy, (2011)

Microstructure, cold workability and strain hardening behavior of Trimodaled AA 6061-TiO2 nanocomposite prepared by mechanical alloying, Mater. Sci. Eng. A 528, 6776-6787.

INTERNATIONAL CONFERENCES1. Sivasankaran, S., Sivaprasad, K. R. Narayanasamy and V. K.

Iyer (2010) Effect of grain refinement on workability of Al 6061 alloy reinforced with 10 wt.% TiO2 composite. International Conference on Powder Metallurgy 2010 (PM10), Jaipur, January 28-30.

2. Narayanasamy,R., K.Sivaprasad, V.Anandakrishnan and S.Sivasankaran (2009) Mechanical Alloying of Aluminium based-metal matrix composites: A Review. 2nd International conference on Recent Advances in Material Processing Technology (RAMPT 2009), February 25-27, 2009, Society for Manufacturing Engineers (SME), National Engineering College, Kovilpatti, 164-170.

INTERNATIONAL JOURNAL

138

REFERENCES RELATED TO LITERATURE REVIEW

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184 2. Prabhu B., Suryanarayana C., An L., Vaidyanathan R. Synthesis and

characterization of high volume fraction Al-Al2O3 nanocomposite powders by high energy milling. Mater. Sci. Eng. A. 2006, 425, 192-200

3. Zhang D.L., Raynova S., Koch C.C., Scattergood R.O., Youssef K.M. Consolidation of a Cu-2.5 vol% Al2O3 powder using high energy mechanical milling. Mater.Sci. Eng.A. 2005, 410-411, 375-380

4. El-Eskandarany M.S. Mechanical solid state mixing for synthesizing of SiCp/Al nanocomposites. J.Alloys Compd. 1998, 279, 263-271

5. Osso D., Tillement O., Le Caer G., Mocellin A. Aluminium- alloy nanocomposite powders by mechnosynthesis. J.Mater.Sci. 1998, 33, 3109-3119

6. Zoz H., Ren H. Processing of ceramic powder using high energy milling. Mater. Sci.Forum. 2000, 343, 955-963.

7. Arik H. Production and characterization of in situ Al4C3 reinforced aluminium based composites produced by mechanical alloying technique. Mater.Des. 2004, 25, 31-40

8. Prabhu B., Suryanarayana C., An L., Vaidyanathan R., Synthesis and characterization of high volume fraction Al-Al2O3 nanocomposites powders by high-energy milling. Materials Science and Engg A. 2006, 425, 192-200 139


based MMCs by Mechanical alloying9. Abdoli H., Salahi E., Farnoush H., Pourazrang K., Evolutions during synthesis

of Al-AlN nanostructured composites powder by mechanical alloying. Journal of Alloys and compounds. 2008, 461, 166-172.

10. Mousavi T., Karimzadeh F., Abbasi M.H., Enayati M.H., Investigation of Ni nanocrystallinezation and the effect of Al2O3 addition by high-energy ball milling. Journal of Materials Processing Technology. 2008, 204, 125-129.

11. Ozdemir I., Ahrens S., Mücklich., Wielage B., Nanocrystalline Al-Al2O3p and SiCp composites produced by high-energy ball milling. Journal of Materials Processing Technology. 2008, 205, 111-118.

12. Khan A.S., Farrokh B., Takacs L., Effect of grain refinement on mechanical properties of ball-milled bulk aluminium. Materials Science and Engg A. 2008, 489, 77-84.

13. Rajkovic V., Bozic D., Jovanovic M.T., Properties of copper matrix reinforced with nano-and micro-sized Al2O3 particles. Journal of Alloys and compounds. 2008, 459, 177-184.

14. Tavoosi M., Karimzadeh F., Enayati M.H., Heidarpour A., Bulk Al-Zn/Al2O3 nanocomposite prepared by reactive milling and hot pressing methods. Journal of Alloys and compounds. 2008, In-press.

15. Varalakshmi S., Kamaraj M., Murty B.S. Synthesis and characterization of nanocrystalline AlFeTiCrZnCu high entropy solid solution by mechanical alloying. J. Alloy Compd. 2008, 460, 253–257. 140


based MMCs by Mechanical alloying16. Tavoosi M., Karimzadeh F., Enayati M.H., Heidarpour A. Bulk Al-Zn/Al2O3

nanocomposite prepared by reactive milling and hot pressing methods. J.Alloy Compd. 2008, in-press

17. Zheng Z.G., Zhong X.C., Zhang Y.H., Yu H.Y., Zeng D.C. Synthesis, structure and magnetic properties of nanocrystalline ZnxMn1-xFe2O4 prepared by ball milling. J.Alloy Compd. 2008, 466, 377-382

18. Yucel Birol. Response to thermal exposure of the mechanically alloyed Al/C powder blends. J.Alloy Compd. 2008, 460, L1-L5

19. Abdoli H., Salahi E., Farnoush H., Pourazrang K. Evaluations during synthesis of Al-AlN-nanostructured composite powder by mechanical alloying. J.Alloy Compd. 2008, 461, 166-172

20. Zhou Y., Xia Z.P., Li Z.Q. Structural evaluation of an Al-Te mixture during ball milling. Mat Charact. 2008, In-press

21. Ismail Ozdemir., Sacha Ahrens, Silke MÜcklich., Bernhard Wielage. Nanocrystalline Al-Al2O3p and SiCp composites produced by high-energy ball milling. J.Mat.Process.Technol.2008, 205, 111-118

22. Mousavi T., Karimzadeh F., Abbasi M.H., Enayati M.H. Investigation of Ni nanocrystallization and the effect of Al2O3 addition by high-energy ball milling. J.Mat.Process.Technol. 2008, 204, 125-129

141


based MMCs by Mechanical alloying23. Ahhtar S Khan., Babak Farrokh., Laszlo Takacs. Effect of grain refinement on

mechanical properties of ball-milled bulk aluminium. Mater.Sci.Eng. A. 2008, 489, 77-84

24. Yong Yang., You Wang., Zheng Wang., Gang Liu., Wei Tian. Preparation and sintering behavior of nanostructured alumina/titania composite powders modified with nano-dopants. Mater.Sci.Eng. A. 2008, 490, 457-464

25. Zhu Xiao., Zhou Li., Shiyun Xiong., Xiaofei Sheng., Mengqi Zhou. Effect of processing of mechanical alloying and powder metallurgy on microstructure and properties of Cu-Al-Ni-Mn alloy. Mater.Sci.Eng. A. 2008, 488, 266-272

26. Reid B Carline., Forrester S Jennifier., Goodshaw J Heather., Kisi H Erich., Suaning J Gregg. A study in the mechanical milling of alumina powder. Ceramic Int. 2008, 34, 1551-1556

27. Al-Aqeeli N, Mendoza-Suarez G, Suryanarayana G, Drew R.A.L. Development of new Al-based nanocomposites by mechanical alloying. Mater.Sci.Eng. A. 2008, 480, 392-396

28. Prabhu B, Suryanarayana C, An L, Vaidyanathan R. Synthesis and characterization of high volume fraction Al–Al2O3 nanocomposite powders by high-energy milling. Mater.Sci.Eng. A. 2006, 425, 192-200

29. Venugopal T, Prasad Rao K, Murty B.S. Mechanical and electrical properties of Cu–Ta nanocomposites prepared by high-energy ball milling. Acta Materialia. 2007, 55, 4439–4445

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Review of workability behavior of Al based MMCs30. Narayanasamy R., Ramesh T., Pandey K.S. Workability studies on cold upsetting of

Al-Al2O3 composite material. Mater.Des.2006, 27, 566-575 31. Narayanasamy R, Ramesh T, Pandey K.S, Pandey S.K. Effect of particle size on new

constitutive relationship of aluminium–iron powder metallurgy composite during cold upsetting.Materials & Design, 2008, 29 (5), 1011-1026

32. R. Narayanasamy, V. Anandakrishnan, K.S. Pandey . Effect of geometric work-hardening and matrix work-hardening on workability and densification of aluminium–3.5% alumina composite during cold upsetting. Materials & Design, 2008, 29(8), 1582-1599

33. R. Narayanasamy, T. Ramesh, K.S. Pandey. Some aspects on cold forging of aluminium–iron powder metallurgy composite under triaxial stress state condition. Materials & Design, 2008, 29(4), 891-903

34. R. Narayanasamy, T. Ramesh, M. Prabhakar, Effect of particle size of SiC in Aluminium matrix on workability and strain hardening behaviour of P/M composite. Materials Science and Engineering: A, 2009, 504 (1-2), 13-23.

35. N. Selvakumar, P. Ganesan, P. Radha, R. Narayanasamy, K.S. Pandey, Modelling the effect of particle size and iron content on forming of Al–Fe composite preforms using neural network.Materials & Design, 2007, 28 (1), 119-130.

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Review of Bimodal / Trimodal Al based MMCs[36]. B.Q. Han, Z. Lee, S.R.Nutt, E.J. Lavernia, F.S. Mohamed. Mechanical properties of an

ultrafine-grained Al-7.5 Pct Mg alloy. Metall. Mater. Trans.A, 2003; 34A: 603-613.[37] C.C. Koch, D.G. Morris, K. Lu and A. Inoue, Ductility of nanostructured materials, MRS

Bulletin Vol. 24(2) (1999), p. 54-58.[38] B. Q. Han, F. A. Mohamed and E. J. Lavernia: Tensile behavior of bulk nanostructured and

ultrafine grained aluminum alloys. Journal of Materials Science Vol. 38(15) (2003), p. 3319.

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[41] G.He, J.Eckert, W. Loser and L.S. Schultz, Novel Ti-base nanostructure–dendrite composite with enhanced plasticity, Nature Mater, 2002, vol.2, pp. 33-37.

[42] V.L. Tellkamp, A. Melmed and E.J. Lavernia; Mechanical behavior and microstructure of a thermally stable bulk nanostructured Al alloy. Metall. Mater. Trans.A, 2001, Vol. 32(9), pp. 2335-43.

[43] Z.Lee, R.Rodriguez, R.W. Hayes, E.J. Lavernia, and S.R. Nutt, Microstructural evolution and deformation of cryomilled nanocrystalline Al-Ti-Cu alloy, Metal. Mater. Trans.A, 2003, vol. 34A, pp. 1473-81.

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Review of Bimodal / Trimodal Al based MMCs[44] B.Q.Han, Z.Lee, D.Witkin, S.Nutt and E.J. Lavernia: Deformation behavior of bimodal

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[45] J.Ye, B.Q. Han, Z. Lee, B. Ahn, S.R. Nutt and J.M. Schoenung: A tri-modal aluminium based composite with super-high strength. Scripta Materialia Vol. 53 (2005), p.481-486.

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146

Thank You

Literature Reviewa. Mechanical alloying of Al based composites

148

Processing Method

Observations Authors

Conventional Al-based Composites-casting, con.P/M route

-Inhomogeneous distribution- Settling of reinforcements and poor wet-ability

Ozdemir et al. (2000)Lee et al. (2001)

Processing Method

Observations Authors

Mechanical alloying (MA) / Mechanical milling (MM)

-Nanostructured materials- Easy to apply-Simple and inexpensive-Fine dispersion of second phase particles-Development of amorphous phase

Zoz and Ren (2000) Arik (2004)Suryanarayana (2001)

Literature Review – Contd..b. Powder Morphological changes

149

Authors Materials

Testing/Processing Methods /

Investigations

Inferences/Findings

Samal et al. (2010)

Al-Cu alloy

MA (0, 10, 25, 35 and 50 h)/SEM

-Particle size reduced from 21 m to 3 m

Jafari et al. (2009)

AA 2024 Al alloy

MM (500 rpm, 10:1, time: 4, 5, 6, 10, 20 and 30 h)

-Irregular shape to equiaxed and almost spherical shaped powder after 30 h- Obtained fine powders

Prabhu et al (2006)

Al-Al2O3

- MM- Particle size (50, 150 and 5 m) -Vol. % (20, 30 and 50 %)

-Uniform distribution of ceramic phase on the matrix-Fine powder with % Al2O3- Matrix reduction with nano Al2O3

Sivasankaran et al. (2011)

AA 6061-Al2O3

-MA (40 h, 280 rpm, 10:1)- 0, 4,8, and 12 wt.% Al2O3

-Steady state attained-Matrix particle size reduction with Al2O3 (131, 88, 44 and 33 μm )

Abdoli et al. (2008)

Al-AlN

-MM (25 h) -Formation of equiaxed particles depend on reinforcement-AlN accelerated the fragmentation

Literature Review – Contd..c. Structural Changes

150

Authors Materials

Testing/Processing Methods /

Investigations

Inferences/Findings

Samal et al. (2010)

Al-Cu alloy

MA (0, 10, 25, 35 and 50 h)/SEM

-Crystallite size and lattice strain decreased with milling time due to grain refinement

Paul et al. (2011

Al95Zn5 MA (300 rpm, BPR: 10:1, Toluene media) (0, 5, 10, 20, 30 and 40h)

-Applied to nanofluid fabrication-Crystallite size was decreased from 181 to 44 nm

Poirier et al.(2010)

Al-Al2O3

- MM- Particle size (4, 80 and 400 nm) -Vol. % (20, 30 and 50 %)

-4 nm Al2O3 produced crystallite size of 90 nm -400 nm Al2O3 produced crystallite size of 310 nm -Nano Al2O3 have impact on structural changes

Sivasankaran et al. (2011)

AA 6061-Al2O3

-MA (40 h, 280 rpm, 10:1)- 0, 4,8, and 12 wt.% Al2O3

-Peak broadened observed with Al2O3

Literature Review – Contd..d. Powder Consolidation

151

Authors

Materials

Testing/Processing Methods / Investigations

Inferences/Findings

Razavi-Tousi et al. (2011)

Al-Al2O3

-MM (1, 3 and 7 vol.%, -39 nm and 500 nm Al2O3-22h, 300 rpm, BPR: 20:1-Cold uniaxial compaction and sintering

-Nano Al2O3 composite exhibited more hindering effect on densification compared to submicron Al2O3 compositei.e. work hardening effect produced by the former one is more

Sameezadeh et al., (2011)

AA 2024-MoSi2

- MA (0, 1, 2, 3, 4 and 5 vol.%) - Hot pressing (470°C, 450 MPa for 75 min)

-Over 97% densification obtained in all samples

Hosseini et al. (2010)

AA 6061-Al2O3

- MM- Particle size (30nm, 1 m and 60 m) -Hot pressed (400ºC, 128 Mpa)

-Density 98.5 (30 nm), 77.5 (1 m) and 62% (60 m)-30 nm Al2O3 nanocomposite produced high hardness and wear resistance

Pérez et al. (2010)

Al-MWCNT

-MA (0 to 2% with step 0.25%)-Sintering-hot extrusion

-Excellent adhesion of nanotubes to Al-matrix i.e. Al can wet CNTs by MA

Literature Review – Contd..f. Hardness

152

Authors

Materials

Testing/Processing Methods

Inferences/Findings

Ozdemir et al. (2008)

Al-Al2O3 and SiCp

MMHardness

-Increasing hardness with HEBM time- Al2O3 composite produced more hardness than SiCp

Abdoli et al. (2008)

Al-AlN MMVickers hardness

- The hardness of MMed composite produced 4.7 times higher than 0h

Hosseini et al. (2010)

AA 6061-3 vol.% Al2O3

MM, Hot pressingAl2O3 (30nm, 1 m and 60 m)

-30 nm Al2O3 -2.26 Gpa-1 m Al2O3-0.92 Gpa-60 m Al2O3-0.74GPa

g. Workability of CG porous materialsAuthors

Materials

Cold upsetting/Processing Methods

Inferences/Findings

Taha et al. (2008)

Al-Al2O3 and SiCp

Stir casting, squeese casting and P/M

-Highest workability obtained in Al-SiCp composite

Narayanasamy et al. (2009)

Al-SiCp -Con. P/M route-Al2O3 (50, 65, and 120 m)-5, 10, 15 and 20 %

-The formability stress index increased with SiC content due to closing of pores - It was increased with SiC particle size due to densification in addition to effective load transfer