Processing, Microstructural And Mechanical Characterization Of Mechanically Alloyed Al-al2o3 ...

117 Pages·2016·3.53 MB·English

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2004
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Pushkar Katiyar
University of Central Florida
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PROCESSING, MICROSTRUCTURAL AND MECHANICAL
CHARACTERIZATION OF MECHANICALLY ALLOYED Al-Al O
2 3
NANOCOMPOSITES

by

PUSHKAR KATIYAR

B. Tech., Jawaharlal Nehru Technological University, Hyderabad, 2001

A thesis submitted in partial fulfillment of the requirements
for the degree of Master of Science
in Materials Science and Engineering
in the Department of Mechanical, Materials, and Aerospace Engineering
in the College of Engineering and Computer Science
at the University of Central Florida
Orlando, Florida

Summer Term
2004

Advisor: Dr. C. Suryanarayana
ABSTRACT

Aluminum-alumina nanocomposites were synthesized using mechanical alloying of
blended component powders of pure constituents. This study was performed on various powder
mixtures with aluminum as the matrix and alumina as the reinforcement with volume fractions
of 20, 30, and 50 % and Al O particle sizes of 50 nm, 150 nm, and 5 µm. X-ray diffraction
2 3
(XRD) and scanning electron microscopy (SEM) techniques were used for the crystal structure
and microstructural characterization of the powders at different stages of milling. Al O powders
2 3
with 50 nm and 150 nm particle size were predominantly of γ-type, while Al O of 5 µm size
2 3
was of α-type. The main goal was to achieve uniform distribution of the Al O ceramic particles
2 3
in the Al matrix, which was achieved on milling for 24 h in a SPEX mill or 100 h in a Fritsch
Pulverisette planetary ball mill. The powders were consolidated in two stages: pre-compaction at
room temperature followed by vacuum hot pressing (VHP) or hot isostatic pressing (HIP)
techniques to a fully dense condition. The effect of reinforcement particle size and volume
fraction on the stress-strain response, elastic modulus and yield strength of the composites was
investigated. Nanoindentation and compression tests were performed to characterize the
composite material. Yield strength of 515 MPa, compressive strength of 685 MPa and elastic
modulus of 36 GPa were obtained from compression tests. Nanoindentation results gave the
yield strength of 336 MPa, maximum shear stress of 194 MPa and an elastic modulus of 42 GPa.
The low elastic modulus values obtained from the above tests might be because of localized
yielding possibly due to residual stresses.

i i
ACKNOWLEDGEMENTS

I am thankful to my parents and my brother who motivated me to pursue a Master’s
degree here in the United States. This thesis is dedicated to their continual love and support to
me in times of blues. I would like to express my sincere thanks to Dr. C. Suryanarayana for
being a great mentor professionally and off the desk, his way of dealing with problems amazes
me to this date, Dr. Raj Vaidyanathan for his supervision and professional approach that led me
into the right track, and Dr. Linan An for his fruitful discussions and invaluable suggestions that
turned out to be a lifesaver. I would also like to thank Dr. S. J. Kalita for his endless support and
encouragement.
I would like to take this opportunity to express my gratitude to all the fellow students
under Dr. Sury’s, Dr. Raj’s and Dr. An’s group especially Dr. Soonjik Hong, Umesh Patil, Vinu
Krishnan, Surendramohan Dakshinamurthy, Sudhir Rajagopalan, Chandrasen Rathod and
Yiguang Wang for helpful discussions and friendly advice. Special thanks to Prudhvi Indukuri
for his supervision in the use of XRD equipment, Zia Rahman for his expert advice while using
the SEM machine, Waheeda Illasarie for her assistance in scheduling the SEM at MCF, Arlene
Ollivierre and Linette Reyes for their assistance pertaining to the ordering of stuff, paper work
preparation and Mr. Abdul Benwali for his technical support.

ii i
TABLE OF CONTENTS

LIST OF FIGURES.......................................................................................................................vi
LIST OF TABLES.......................................................................................................................viii
CHAPTER 1: INTRODUCTION....................................................................................................1
1.1 Motivation.............................................................................................................................1
1.2 Organization..........................................................................................................................3
CHAPTER 2: LITERATURE SURVEY.........................................................................................5
2.1 Introduction...........................................................................................................................5
2.2 Processing Methods...............................................................................................................7
2.2.1 Infiltration Method..........................................................................................................8
2.2.2 Displacement Reaction Method....................................................................................13
2.2.3 Liquid Metallurgy Method............................................................................................16
2.2.4 Die-Casting Method......................................................................................................19
2.2.5 Anodizing Method.........................................................................................................20
2.3 Properties.............................................................................................................................22
2.4 Applications.........................................................................................................................31
CHAPTER 3: MECHANICAL ALLOYING................................................................................33
3.1 Introduction.........................................................................................................................33
3.2 Process of Mechanical Alloying..........................................................................................34
3.3 Important Components of Milling.......................................................................................37
3.3.1 Raw Materials...............................................................................................................37
3.3.2 Types of Mills...............................................................................................................38
3.3.2.1 SPEX Shaker Mills.................................................................................................38
3.3.2.2 Planetary Mills........................................................................................................39
3.3.3 Process Variables..........................................................................................................40
3.3.3.1 Milling Speed and Time..........................................................................................41
3.3.3.2 Milling Medium......................................................................................................41
3.3.3.3 Ball-to-Powder Weight Ratio.................................................................................42
3.3.3.4 Process Control Agent............................................................................................42
CHAPTER 4: EXPERIMENTAL PROCEDURES.......................................................................44
4.1 Raw Materials......................................................................................................................44
4.2 Powder Synthesis.................................................................................................................44
4.3 Structural Analysis..............................................................................................................50
4.3.1 X-ray Diffraction...........................................................................................................50
4.3.2 Scanning Electron Microscopy (SEM).........................................................................51
4.4 Consolidation of Alloyed Powders......................................................................................52
4.4.1 Pre-Compaction.............................................................................................................52
4.4.2 Hot Isostatic Pressing (HIPing).....................................................................................57
4.5 Mechanical Characterization...............................................................................................59
iv
4.5.1 Compression Testing.....................................................................................................59
4.5.2 Nanoindentation............................................................................................................60
CHAPTER 5: RESULTS AND DISCUSSION.............................................................................63
5.1 X-ray Diffraction.................................................................................................................63
5.1.1 X-ray Diffraction Results of As-Received Powders.....................................................71
5.1.2 X-ray Diffraction Results of Milled Powders...............................................................77
5.2 SEM Analysis......................................................................................................................78
5.3 Consolidation.......................................................................................................................88
5.4 Compression Testing...........................................................................................................91
5.5 Nanoindentation...................................................................................................................96
CHAPTER 6: SUMMARY AND CONCLUSIONS...................................................................103
LIST OF REFERENCES.............................................................................................................105

v
LIST OF FIGURES

Figure 1.1: Schematic representation of the relationship between λ, d and f .................................2
v
Figure 2.1: Types of MMCs, based on reinforcements [4]..............................................................6
Figure 2.2: Basic principle of medium pressure infiltration technique [9]......................................8
Figure 2.3: Microstructure of the material with clustered fibers [9]................................................9
Figure 2.4: Optical micrographs of (a) interpenetrating phase ceramic-matrix composite-34
vol.%, (b) discontinuous reinforced composites; light gray phase is Al and dark gray is Al O (c)
2 3
SEM micrograph of IPC34 where the lighter phase is Al O and the darker phase is Al [10]......12
2 3
Figure 2.5: Magnified SEM image of particles in Al matrix with (a) CuAl phase (b) CuO and (c)
2
CuO and SiO [12].........................................................................................................................15
2
Figure 2.6: (a) TEM images of insitu Al O particle in the matrix and (b) magnified image of α-
2 3
Al O particle [12]..........................................................................................................................15
2 3
Figure 2.7: TEM Micrograph of Al-Al O composites, (a) 1 vol. % and (b) 4 vol. % Al O [15]18
2 3 2 3
Figure 2.8: Schematic diagram showing the manufacturing of Al-Al O composites using
2 3
anodizing of Aluminum foils [17]..................................................................................................21
Figure 2.9: Micrograph of Al-Al O composite with (a) 15 vol. %, and (b) 5 vol. % Al O [17].21
2 3 2 3
Figure 2.10: Stress vs. vol. fraction for matrix, fiber and composite [17].....................................30
Figure 3.1: Hardened steel vial set used for SPEX Certiprep mixer mill......................................36
Figure 3.2: Schematic representation of (a) Powder particles trapped between the balls, (b)
milling by crushing of particles between the vial surface and balls [23].......................................36
Figure 3.3: SPEX Certiprep 8000D mixer mill.............................................................................38
Figure 3.4: FRITSCH GmbH, planetary mill................................................................................40
Figure 4.1: Pre-compaction die set.................................................................................................53
Figure 4.2: Disintegrated specimen with layers of graphite...........................................................53
Figure 4.3: Sample piece after pre-compaction.............................................................................55
Figure 4.4: Thin walled Al tube used for HIPing...........................................................................55
Figure 4.5: Actual length of container (Aluminum tube) after welding........................................56
Figure 4.6: Position of the samples in the tube..............................................................................56
Figure 4.7: Layout of the hot isostatic press [30]...........................................................................57
Figure 4.8: Load-Displacement curve with labeled parameters [33].............................................60
Figure 5.1: Standard XRD pattern for alumina [38]......................................................................64
Figure 5.2: Standard XRD pattern for pure Aluminum [38]..........................................................64
Figure 5.3: Experimental XRD pattern of as-received pure aluminum powder............................65
Figure 5.4: Experimental XRD pattern of as-received pure alumina.............................................65
Figure 5.5: XRD patterns for Al-20vol. % Al O (50 nm) as a function of milling time..............66
2 3
Figure 5.6: XRD patterns for Al-20vol. % Al O (150 nm) as a function of milling time............66
2 3
Figure 5.7: XRD patterns for Al-20 vol. % Al O (50 nm) using Fritsch mill..............................67
2 3
Figure 5.8: XRD patterns for Al-20 vol. % Al O (5 µm) milled for 24 h in a SPEX mill...........68
2 3
Figure 5.9: XRD patterns for Al-30 vol. % Al O (50 nm) at different milling times...................68
2 3
v i
Figure 5.10: XRD patterns for Al-30 vol. % Al O , 150 nm milled for 100 h in a Fritsch
2 3
Pulverisette P5 mill........................................................................................................................69
Figure 5.11: XRD patterns for Al-30 vol. % Al O , 5 µm milled for 24 h in a SPEX mill...........70
2 3
Figure 5.12: XRD patterns for Al-20 vol. % Al O , (50 nm) milled for different times using a
2 3
BPR of 5:1......................................................................................................................................70
Figure 5.13: XRD patterns for Al-50 vol. % Al O of different particle sizes milled for 24 h in a
2 3
SPEX mill.......................................................................................................................................71
Figure 5.14: Standard XRD patterns transition alumina [39]........................................................73
Figure 5.15: SEM images of Al-20 vol. % Al O , 50 nm powders milled for (a) 1 h, (b) 7 h, (c)
2 3
15 h, (d) 20 h and (e) 24 h in a SPEX mill.....................................................................................79
Figure 5.16: SEM images of Al-20 vol. % Al O , 50 nm powders milled for (a) 50 h and (b) 100
2 3
h in a Fritsch Pulverisette mill........................................................................................................81
Figure 5.17: SEM images of Al-20 vol. % Al O , 50 nm, 5:1 BPR powders milled for (a) 7 h and
2 3
(b) 15 h, (c) 25 h and (d) 30 h in a SPEX mill...............................................................................82
Figure 5.18: SEM images of Al-20 vol. % Al O , 150 nm powders milled for (a) 3 h, (b) 8 h, (c)
2 3
15 h and (d) 24 h in a SPEX mill...................................................................................................83
Figure 5.19: SEM image of Al-20 vol. % Al O , 5 µm powder milled for 24 h in a SPEX mill..84
2 3
Figure 5.20: SEM images of Al-30 vol. % Al O , 50 nm powders milled for (a) 14 h, (b) 21 h,
2 3
and (c) 24 h in a SPEX mill............................................................................................................85
Figure 5.21: SEM image of Al-30 vol. % Al O , 150 nm powder milled for 24 h in a SPEX mill86
2 3
Figure 5.22: SEM image of Al-30 vol. % Al O , 5 µm powder milled for 24 h in a SPEX mill..86
2 3
Figure 5.23: SEM image of Al-50 vol. % Al O , 50 nm powder milled for 24 h in a SPEX mill.87
2 3
Figure 5.24: SEM image of Al-50 vol. % Al O , 150 nm powder milled for 24 h in a SPEX mill87
2 3
Figure 5.25: SEM image of Al-50 vol. % Al O , 5 µm powder milled for 24 h in a SPEX mill..88
2 3
Figure 5.26: Al-2024, T3 tube for HIPing.....................................................................................90
Figure 5.27: Load - Displacement curve for Al-20 vol. % Al O , 150 nm particle size................92
2 3
Figure 5.28: Engineering stress - strain response of Al-20 vol. % Al O , 150 nm particle size....93
2 3
Figure 5.29: Corrected load-displacement curve for Al-20 vol. % Al O , 150 nm.......................93
2 3
Figure 5.30: Corrected Engineering Stress-Strain curve for Al-20 vol. % Al O , 150 nm............94
2 3
Figure 5.31: Yield stress and elastic modulus calculations for Al-20 vol. % Al O , 150 nm........94
2 3
Figure 5.32: Machine displacement vs. applied load.....................................................................97
Figure 5.33: Elastic response of standard fused quartz sample......................................................98
Figure 5.34: Representative load-displacement curve from nanoindentation of Al-20 vol. %
Al O composite.............................................................................................................................99
2 3
Figure 5.35: log P vs. log h (loading)...........................................................................................100
Figure 5.36: 3/2 fit to the elastic region of the loading portion of the P-h curve.........................101

vi i
LIST OF TABLES

Table 2.1: Nominal properties of matrix and alumina fibers.........................................................24
Table 2.2: Elastic properties of composite with 50 vol. % alumina...............................................24
Table 2.3: Measured elastic properties indicating higher stiffness of the IPCs.............................25
Table 2.4: Mechanical properties of three different composites....................................................26
Table 2.5: Grain sizes and hardness of composites........................................................................27
Table 2.6: Mechanical properties of the composites with 3-26 vol. % Al O ...............................28
2 3
Table 2.7: Different processing methods and properties................................................................32
Table 4.1: Data sheet for Al-20 vol. % Al O (50 nm, 150 nm and 5 µm)....................................45
2 3
Table 4.2: Data sheet for bulk production of Al-20 vol. % Al O (50 nm and 150 nm)................47
2 3
Table 4.3: Data sheet for Al-30 vol. % Al O (50 nm, 150 nm and 5 µm)....................................48
2 3
Table 4.4: Data sheet for Al-20 vol. % Al O (50 nm, 5:1 BPR)..................................................49
2 3
Table 4.5: Data sheet for Al-50 vol. % Al O (50 nm, 150 nm and 5 µm)....................................50
2 3
Table 5.1: Details of indexing the XRD pattern of as-received pure Aluminum...........................72
Table 5.2a: Standard X-ray diffraction data of α-alumina.............................................................74
Table 5.2b: Standard X-ray diffraction data of γ-alumina.............................................................74
Table 5.2c: Standard X-ray diffraction data of θ-alumina.............................................................75
Table 5.2d: Standard X-ray diffraction data of δ-alumina.............................................................75
Table 5.3a: Comparison of the experimental 2θ and d values for pure alumina (50 nm) with those
expected from different polymorphs..............................................................................................76
Table 5.3b: Comparison of the experimental 2θ and d values for pure alumina (150 nm) with
those expected from different polymorphs.....................................................................................76
Table 5.3c: Comparison of the experimental 2θ and d values for pure alumina (5 µm) with those
expected from different polymorphs..............................................................................................77
Table 5.4: Details of indexing the XRD pattern, Al-20 vol. % 50 nm Al O ................................77
2 3
Table 5.5: Density variation before and after HIPing....................................................................89
Table 5.6: Comparison of results from literature and experiments..............................................102

vi ii
CHAPTER 1: INTRODUCTION

1.1 Motivation

Recent research in the field of aluminum-based metal matrix composites has brought out
the immense potential in terms of their applications and development of different fabrication
methods. Superior mechanical properties and high strength-to-weight ratio of such materials
have led to an increased interest in the automobile and aerospace industries in which saving the
weight of the component is a critical issue. Several fabrication techniques have been developed
in recent years to manufacture the composites with specific properties in mind. The aluminum
matrix can be reinforced with a variety of ceramic particles of different shapes and sizes to
achieve the desired properties. But, the principal difficulty in achieving the properties is the
inability to produce the desired connectivity and spatial distribution of the phases for a given
volume fraction. Among other things, the strength of the composite depends on the spacing
between the reinforcement particles.
The relationship between the inter-particle spacing, λ, particle size, d and the volume
fraction of the reinforcements, f is given by the equation [1]:
v
λ = d (f -1/3-1) (1.1)
v
The main assumption here is that the particles are considered to be of equal size,
periodically spaced and cubic in shape. The above equation can be used as a guideline for
1