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
By
S.SIVASANKARAN
414108054
Research Supervisor
Dr.R.NARAYANASAMY, Professor,
Department of Production Engg.,
NIT, Tiruchirappalli - 15
Research Co-Supervisor
Dr. K.SIVA PRASAD, Assistant Professor,
Department of Metallurgical and Materials Engg.,

Doctoral Committee Members
External Member
Dr. G.Chandramohan, Retired Professor,
Dept. of Mechanical Engg.
PSG College of Technology,
Coimbatore – 641 004
Internal Member
Dr. V. Senthil Kumar, Assistant Professor,
Dept. of Production Engg.,
Chairman
Dr.T.SELVARAJ, Professor,
Internal Member
Dr. C. Sathiya Narayanan, Assistant
Professor,
Dept. of Production Engg.
Research Supervisor
Dr.R.NARAYANASAMY,
Professor,
Research Co-Supervisor
Dr. K.SIVA PRASAD, Assistant Professor,
Dept. of Met. and Materials Engg.,

Outline of Thesis presentation
1) Introduction
2) Literature review
3) Research Gap, Problem defined, Objectives and Work plan
4) Experimental procedure
5) Results and Discussion
5.1. Powder surface morphology evaluation
5.2. Flow characteristics of powders
5.3. Structural evaluation of mechanically alloyed powders
5.4. Compressibility behavior of micro and nanocomposite
powders
5.5. Evaluation of compaction equations
5.6. Green mechanical strength and sintering behavior
5.7. Grain refinement and its formability
5.8. Trimodaled nanocomposite and its formability
5.9. Modeling of compaction behavior using ANFIS
6) Conclusions and Scope for future work
7) Publications and References

1.0 Introduction
Composite Materials – Definition
Metal 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 Matrix
Ceramic 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)
Powders of
Metal A
Powders of
Metal B
Hardened
steel or WC
balls
High velocity of the ball
Fractured
Powders
Alloy
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 Objectives
1. 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
Microcomposite
Blending
Nanocomposite
MA
1. Powder characterization
2. Flow characteristics
3. Compressibility behavior
4. Green compressive strength
5. 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 composites 14

Fig. Schematic diagram of high-energy wet planetary ball milling principle
(Mechanical Alloying) for nano-composites 15
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/Investigation
Trimodaled
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)

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 powders
33

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 time
36

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 intensity 39
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 time
40
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 time 41
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 angle 43
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 milling 44
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 reinforcement 45
Structural changes as function of reinforcement

5.3 X-ray diffraction (XRD) patterns of Microcomposite
46
Intensity,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
BPA
D






1
1
ln

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 ln
1
BPA
D

2) Heckel :
22
1
1
ln BPA
D







3) Ge : 33 log
1
1
lnlog BPA
D





4) Panelli and Filho :
44
1
1
ln BPA
D







5) Kawakita :
5
5
0
B
P
A
DD
D







6) Shapiro :
    5.0
01ln1ln bPkPDD 
Non-Linear Equations:
7) Cooper and Eaton:





 





 



P
A
B
P
A
B
D
DD 7
7
6
6
0
0
exp
1
8) Zwan and Siskens :





 



P
A
B
D
DD 8
8
0
0
exp
1

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
density,
g/cm3
Flow
rate,
s/50g
Theoretic
al density,
g/cm3
Relative
apparent
density
(D0)
0 652.50 131.20 1.36060 1.43850 0.26910 2.70000 0.50393
2 614.20 122.30 1.35121 1.42856 0.28300 2.72280 0.49626
4 585.00 104.80 1.34830 1.42000 0.29780 2.74560 0.49108
6 553.50 83.50 1.33246 1.39467 0.32411 2.76840 0.48131
8 504.60 67.75 1.31980 1.36450 0.35440 2.79120 0.47284
10 484.00 60.45 1.30848 1.35215 0.42356 2.81400 0.46499
12 462.00 56.46 1.29850 1.34020 0.49380 2.83680 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 Powder
Eq. (1) Eq. (2) Eq. (3)
A1 B1 R2
A2
(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
2
AA 6061 + 2%
TiO2
-0.0735 1.5527 0.9717 0.1297 1.8220 0.9387 0.3025 -0.4054 0.9901
3
AA 6061 + 4%
TiO2
-0.0817 1.6137 0.9702 0.1333 1.7110 0.9492 0.3176 -0.4612 0.9823
4
AA 6061 + 6%
TiO2
-0.0860 1.6492 0.9739 0.1295 1.6527 0.9586 0.3160 -0.4711 0.9849
5
AA 6061 + 8%
TiO2
-0.0902 1.6837 0.9755 0.1230 1.6070 0.9600 0.3122 -0.4749 0.9859
6
AA 6061 +
10% TiO2
-0.1005 1.7613 0.9779 0.1294 1.4843 0.9688 0.3214 -0.5176 0.9910
7
AA 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 R2
k
(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 Mpa
Both-375 to 1000 Mpa
PD>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





 



P
k
a
D
DD p
p exp
1 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 reinforcement
Microcomosite
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 MPa
Mixed Al Kα
5
mTi Kα O Kα

73
5.6 Mapping of AA 6061-10 TiO2 – 40 h, post-compact, 500 MPa
Mixed Al Kα
5 m
Ti 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
78
Fig. 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 a-Al (1602) + TiO2 (45) + Al2O3 (38)
5 a-Al (792) + TiO2 (44) + Al2O3 (38)
10 a-Al (545) + TiO2 (41) + Al2O3 (38)
20 a-Al (374) + TiO2 (40) + Al2O3 (38)
30 a-Al (304) + TiO2 (40) + Al2O3 (38)
40 a-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 clusters 89
(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
(sy), 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









f
z
h
h0
ln1) True axial strain 2) True hoop strain 




 
 2
0
22
3
2
ln
2
1
D
DD CB

3) True effective strain  
21
2
2
22
2
)1(
3
)2(
422
)2(3
2










 R
R
z
zzeff




4) True axial stress
areasurfacecontact
load
z s 5) True hoop stress z
RR
R
s
a
a
s 







 22
2
22
2
6) True hydrostatic stress
3
)2( ss
s

 z
m
7) True effective stress
  21
2
2222
12
)2(2









R
R zz
eff
 sssss
s
8) Formability stress index
eff
m
s
s
s
3
 9) Instantaneous Poisson’s ratio
z
i


 

10) Instantaneous strain hardening index



















1
1
)(
)(
ln
)(
)(
ln
ieff
ieff
ieff
ieff
in


s
s

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 area
Interparticle 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 composite 96
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

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 a-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.

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

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

(a)
5.8 XRD study of Trimodaled composites
109
Fig. 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)
111
wt.% CG content. (a) As-sintered (b) As-deformed

(b)
112
wt.% CG content. (a) As-sintered (b) As-deformed

113
Fig. Initial and final diffraction peaks of a-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
composite 116
• Max 0.34 for 0% CG
• Max 0.47 for 30% CG
• s increases steadily
with CG content due to
soft parent phase

Fig. Variation of instantaneous Poisson’s ratio with true effective strain with true
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
nanocomposite
119
•%CW for 30%CG 6 times >0%CG

120
Table . Room temperature mechanical properties of present work and others for comparison.
Material Microstructure
Ultimate
strength
(MPa)
Strain-to-
failure
(%)
References
MA of 0% CG AA 6061-TiO2
composite
Bimodal 870ICU 2.6ICU
Present work
composite
Trimodal 884ICU 3.3ICU
composite
composite
composite
composite
composite
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
deformatio
n
As-
sintered
fractional
porosity
As-
deformed
fractional
porosity
True
effective
toughness
(MPa)
Strain
hardening
toughness
index
0 2.814 2.4231 2.4366 0.5574 0.1389 0.1341 55.2362 0.0098
5 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 0.1201 118.1677 0.0195
20 2.7912 2.4311 2.4730 1.7219 0.1290 0.1140 152.6851 0.0252
25 2.7855 2.4311 2.4825 2.1123 0.1272 0.1087 212.3909 0.0349
30 2.7798 2.4376 2.5052 2.7752 0.1231 0.0987 385.5891 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
p
l
p
llll
l
pp
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

123
Fig. The ANFIS architecture for predicting relative density of the post-
compacts
84 – Total data sets
49-Training
35-Testing
18-Validation (New)

124
Linguistics variables for
Percentage of reinforcement
(X1)
Lowest
Lower
Low
Medium
High
Higher
Highest
compaction pressure (X2)
Lowest
Lower
Low
Medium
High
Higher
Highest
Linguistic variable used in ANFIS architecture
relative density (Y)
Extreme Low
Lowest
Lower
Low
Almost Low
Under Medium
Premedium
Medium
Over Medium
Upper Medium
Almost High
High
Higher
Highest
Extreme High

125
Fig. Initial and final triangular MF of percentage of nano titania content in NC
matrix, wt.%

126
Fig. Initial and final triangular membership function of compaction pressure
(P), MPa

127
Fig. 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)
Measured
ANFIS MRA
Predicted Error, % Predicted Error, %
1 0 375 0.90831 0.91854 -1.12703 0.88734 2.30820
2 0 625 0.93804 0.93512 0.31181 0.91541 2.41346
3 0 875 0.95812 0.95755 0.05945 0.94347 1.52868
4 0 1125 0.96882 0.97022 -0.14535 0.97154 -0.28073
5 0 1375 0.97259 0.97217 0.04274 0.99960 -2.77717
6 2 375 0.89612 0.89807 -0.21679 0.88010 1.78839
7 2 625 0.93579 0.93512 0.07157 0.90816 2.95232
8 2 875 0.95479 0.95462 0.01728 0.93623 1.94390
9 2 1125 0.96491 0.96535 -0.04492 0.96429 0.06456
10 2 1375 0.96880 0.96827 0.05449 0.99236 -2.43137
11 4 375 0.88255 0.87564 0.78270 0.87285 1.09827
12 4 625 0.93050 0.93317 -0.28696 0.90092 3.17904
13 4 875 0.95122 0.95170 -0.04969 0.92898 2.33810
14 4 1125 0.96101 0.96047 0.05559 0.95705 0.41193
15 4 1375 0.96737 0.96730 0.00700 0.98511 -1.83457
16 6 375 0.87571 0.86881 0.78808 0.86561 1.15382
17 6 625 0.92420 0.92829 -0.44299 0.89368 3.30285
18 6 875 0.94431 0.94390 0.04437 0.92174 2.39061
19 6 1125 0.95611 0.95560 0.05392 0.94980 0.65974
20 6 1375 0.96453 0.96437 0.01650 0.97787 -1.38278
21 8 375 0.86885 0.86101 0.90226 0.85837 1.20674
22 8 625 0.91786 0.92244 -0.49992 0.88643 3.42357
23 8 875 0.93724 0.93707 0.01790 0.91450 2.42643
24 8 1125 0.95114 0.95072 0.04389 0.94256 0.90184
25 8 1375 0.96016 0.96047 -0.03269 0.97063 -1.09016
26 10 375 0.85912 0.85614 0.34761 0.85112 0.93117
27 10 625 0.90874 0.91074 -0.22010 0.87919 3.25220
28 10 875 0.93137 0.93219 -0.08897 0.90725 2.58900
29 10 1125 0.94611 0.94487 0.13121 0.93532 1.14095
30 10 1375 0.95575 0.95560 0.01590 0.96338 -0.79869
31 12 375 0.84717 0.85029 -0.36756 0.84388 0.38864
32 12 625 0.89989 0.89904 0.09411 0.87194 3.10521
33 12 875 0.92509 0.92732 -0.24066 0.90001 2.71144
34 12 1125 0.94097 0.94000 0.10353 0.92807 1.37044
35 12 1375 0.95110 0.95170 -0.06248 0.95614 -0.52956
Maximum percentage of error 0.90226 3.42357
Minimum percentage of error -1.12703 -2.77717
Mean percentage of error 0.00388 1.13876
Correlation 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.No
Percentage 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 Conclusions
Further, 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 CONFERENCES
1. 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

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Literature Review
a. 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 Materia
ls
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
Sivasankar
an 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

c. Structural Changes
150
Authors Material
s
Testing/Processing
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
Sivasankar
an 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

d. Powder Consolidation
151
Authors Materials Testing/Processing
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 composite
i.e. work hardening effect produced
by the former one is more
Sameeza
deh 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
MM
Hardness
-Increasing hardness with HEBM time
- Al2O3 composite produced more
hardness than SiCp
Abdoli et
al. (2008)
Al-AlN MM
Vickers hardness
- The hardness of MMed composite
produced 4.7 times higher than 0h
Hosseini
et al.
(2010)
AA 6061-3
vol.%
Al2O3
MM, Hot pressing
Al2O3 (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 materials
Authors 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
Narayana
samy 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

Dr.R.Narayanasamy, Dr.S.Sivasankaran and Dr.K.Siva Prasad on Mechanical Alloying

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