Metallic Amorphous Alloy Reinforcements in Light Metal Matrices

117 Pages·2015·5.14 MB·English

by  S. Jayalakshmi

SPRINGER BRIEFS IN MATERIALS
S. Jayalakshmi
M. Gupta
Metallic
Amorphous Alloy
Reinforcements
in Light Metal
Matrices
123
SpringerBriefs in Materials
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S. Jayalakshmi (cid:129) M. Gupta
Metallic Amorphous Alloy
Reinforcements in Light
Metal Matrices
S. Jayalakshmi M. Gupta
Department of Mechanical Engineering Department of Mechanical Engineering
Bannari Amman Institute of Technology National University of Singapore
Sathyamangalam, Tamil Nadu, India Singapore, Singapore
ISSN 2192-1091 ISSN 2192-1105 (electronic)
SpringerBriefs in Materials
ISBN 978-3-319-15015-4 ISBN 978-3-319-15016-1 (eBook)
DOI 10.1007/978-3-319-15016-1
Library of Congress Control Number: 2014960033
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© S. Jayalakshmi and M. Gupta 2015
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Contents
1 Introduction ................................................................................................. 1
1.1 Background .......................................................................................... 1
1.2 Metal Matrix Composites ..................................................................... 2
1.2.1 Processing of MMCs/LMMCs ................................................. 2
1.2.2 Properties, Applications, and Limitations
of MMCs/LMMCs ................................................................... 3
1.3 Metallic Amorphous Alloys ................................................................. 4
References ..................................................................................................... 5
2 Light Metal Matrix Composites ................................................................ 7
2.1 Background .......................................................................................... 7
2.2 Characteristics of MMCs ..................................................................... 8
2.2.1 Importance of Interfacial Bonding ........................................... 11
2.2.2 Role of the Metallic Matrix ...................................................... 12
2.3 Processing of LMMCs ......................................................................... 13
2.3.1 Liquid-State Processes ............................................................. 13
2.3.2 Solid State Processes ................................................................ 21
2.3.3 Semisolid State Processes ........................................................ 25
2.3.4 Other Processes ........................................................................ 28
2.4 Strengthening Mechanisms in LMMCs ............................................... 31
2.4.1 Strength Prediction ................................................................... 32
2.4.2 Fracture Mechanisms ............................................................... 33
2.5 Microstructural and Mechanical Properties of LMMCs ...................... 34
2.5.1 Al-Composites ......................................................................... 34
2.5.2 Mg Composites ........................................................................ 40
2.6 Limitations ........................................................................................... 53
References ..................................................................................................... 53
v
vi Contents
3 Amorphous Alloys/Bulk Metallic Glasses (BMG) .................................. 59
3.1 Background ........................................................................................ 59
3.1.1 Formation and Characteristics
of Amorphous Alloys/ BMG ................................................. 60
3.2 Preparation Methods .......................................................................... 67
3.2.1 Rapid Solidifi cation Processes ............................................... 67
3.2.2 Methods for Producing BMG ................................................ 69
3.2.3 Mechanical Alloying .............................................................. 70
3.3 Structural, Thermal, and Mechanical Properties ................................ 72
3.4 Limitations ......................................................................................... 80
References ................................................................................................... 82
4 Light Metal Matrix Composites with Amorphous
Alloys/Bulk Metallic Glass Reinforcements (BMG) .............................. 85
4.1 Introduction ........................................................................................ 85
4.2 Synthesis, Matrix Reinforcement Selection, and Properties .............. 86
4.2.1 Liquid State Processing: Infi ltration Method ......................... 86
4.2.2 Solid State Processing: Powder
Metallurgy-Based Methods .................................................... 89
4.2.3 Other Methods/Systems ......................................................... 104
4.3 Conclusions ........................................................................................ 105
References ................................................................................................... 105
5 Future Work .............................................................................................. 107
5.1 Future Research and Applicative Prospects ....................................... 107
Index ................................................................................................................. 109
Chapter 1
Introduction
Abstract L ight metal matrix composites are briefl y introduced. The various
c onventional ceramic reinforcements (micro-/nano-size) that are used to make the
composites and the MMC processing techniques are mentioned. The properties,
applications, and limitations of metal matrix composites are summarized. In view of
the limitations of ceramic reinforcements, metallic amorphous alloys are proposed
as alternate reinforcement materials. Their inherent superior properties that can
contribute to the enhanced properties of the composites are highlighted.
Keywords Light metals • Metal matrix composites • Ceramic micro-/nano-scale
reinforcements • Processing and properties • Metallic amorphous alloys
reinforcements
1.1 Background
G lobal concern over the energy crisis that is being faced worldwide has seriously
pushed research to identify effi cient and robust solutions to meet the need. Rapid
depletion of oil reserves, increasing demand for fuel effi ciency, and regulations on
emission reduction has turned the attention towards lightweight materials. Research
on these materials is largely focused to achieve multiple-performance reliability,
along with easier material processing, machinability/formability, and high load-
bearing capacity/structural strength. Energy effi ciency, recyclability, and sustai-
nability are also in the focus. Given this context, R&D of Al and Mg is of great
interest, especially for weight-critical applications such as in automotive, aviation,
sports, electronics, and communication sectors (Rohatgi 1996; Miracle 2005 ;
Kainer 2 006; Sharon and Gupta 2 011 ). In comparison with the density of steel
(8.1 g/cc), Al and Mg have densities of 2.74 and 1.74 g/cc, respectively, and are
therefore the lightest among the structural metals. To note, they offer high specifi c
strength properties, provide energy/fuel effi ciency, and are recyclable. Al-alloys
exhibit excellent ductility, superior resistance to corrosion, and have good thermal
and electrical conductivities. Mg-alloys possess excellent castability, machinability,
damping capacity, impact, and dent resistance. Both Al- and Mg-alloys can be
© S. Jayalakshmi and M. Gupta 2015 1
S. Jayalakshmi, M. Gupta, Metallic Amorphous Alloy Reinforcements
in Light Metal Matrices, SpringerBriefs in Materials,
DOI 10.1007/978-3-319-15016-1_1
2 1 Introduction
precipitation hardened which gives them fl exibility in attaining properties suitable
for a wide variety of commercial/industrial applications (Miller et al. 2 000 ;
Mordike and Ebert 2 001 ).
Applications for high-strength light metal components made of Al and Mg
are constantly growing. For instance, using these metals in automobile engine and
chassis components reduces weight and lowers fuel consumption/emissions, thereby
signifi cantly contributing towards fuel economy. As an example, replacing the
existing cast iron engine block (~84.6 kg) in a V6 3.0 L six-cylinder car by Mg
(~30 kg) would result in an overall weight reduction of ~65 %. The increasing use
of Al- and Mg-based materials in the automotive industry is an excellent example of
materials selection, wherein factors such as material availability, processability,
cost, properties, environmental issues, recyclability, and fuel effi ciency are all taken
into account, together.
1.2 Metal Matrix Composites
D espite the fact that Al- and Mg-alloys have several attractive properties, they do not
completely satisfy the overall requirement in applications, where the components are
required to withstand high mechanical/thermal stresses and also under tribological
conditions. Hence, there arises a need to improve their properties so to realize their
full potential in commercial applications. A reliable route to achieve this objective is
to make composites from the light metals/alloys (Chawla and Chawla 2 006 ).
Composites are combinations of dissimilar materials produced to achieve desired
properties. Owing to the increasing demand for lightweight materials for structural
applications in automobile and aerospace industries, metal matrix composites
(MMCs) have become popular. MMCs are based on the principle of incorporating a
high performance second phase (oxides, carbide ceramics such as SiC, Al O , B C,
2 3 4
and TiN of known volume fraction, V ) in a conventional engineering material (here,
f
light metal matrix such as Al, Ti, and Mg). The reinforcement phase in the MMC is
the secondary phase. The reinforcements are classifi ed into two major categories—
continuous reinforcements and discontinuous reinforcements. Due to its high stiff-
ness and high strength, the reinforcement is the main load-bearing member in the
composite. Reinforcements in MMCs are usually ceramics in the form of fi bers,
whiskers, or particles. In the composite, the morphology and nature of the reinforce-
ments are very important in controlling the fi nal properties, as their interaction with
the matrix would alter the MMC’s microstructure, properties, and performance.
1.2.1 Processing of MMCs/LMMCs
Conventional composites are produced by liquid, solid, and semi-solid state
p rocesses. The choice of the processing route depends on several factors such as the
reinforcement type, its distribution, matrix-particle bonding, control of matrix micro-
structure, process simplicity, and cost-effectiveness (Chawla and Chawla 2 006 ).
1.2 Metal Matrix Composites 3
Liquid-state processes . Liquid-state processing routes are attractive as they are
relatively simple, cost-effective, and are potentially scalable to industrial level.
Liquid-state processes involve the incorporation of reinforcement into the molten
metal followed by casting. Direct addition of reinforcements into the melt or incor-
poration in the form of fi ber/particle preforms is usually employed. Some of the
liquid-state processing routes include stir casting, ultrasonic-assisted casting, infi l-
tration techniques, and disintegrated melt deposition method.
Solid-state processes . Solid-state processes are based on powder metallurgy (PM)
methods, capable of producing near-net shape components. PM processes usually
involve: blending of matrix alloy and reinforcing phase powders; compacting the
blend, usually by cold pressing. The green compacts are then consolidated by different
routes such as direct sintering, hot isostatic pressing (HIP), vacuum HIP, hot extrusion
or cold sintering, microwave-assisted sintering, and spark plasma sintering.
Semi-solid state processes. In semi-solid state processes, incorporation of the rein-
forcements in matrix metal is conducted when a matrix is in semi-solid state (slurry),
as it facilitates: (1) uniform dispersion of reinforcements, (2) eliminates settling of
denser reinforcement due to slurry-state, and (3) eliminates porosity (that usually
occurs due to voids generated at the molten metal/particle interface).
1.2.2 Properties, Applications, and Limitations
of MMCs/LMMCs
Conventional light metal matrix composites (LMMCs) are incorporated with various
micron-sized stronger/stiffer nonmetallic/ceramic reinforcements (e.g., Al O , SiC,
2 3
C) (Polmear 1 995 ; Brook 1 998 ; Avedesian and Baker 1 999 ) which provide:
• Increased mechanical strength
• Higher wear resistance
• Improved thermal expansion
• Enhanced thermal stability
D ue in part to these reasons, light metal-based MMCs have been used in some
products related to automotive, electronic packaging, industrial products, and recre-
ational goods, such as pickup truck drive shafts, brake rotors/pads and drums, diesel
engine pistons, aeronautic engine fan, exit guide vanes, aircraft ventral fi ns, fuel access
covers, bicycle components, golf clubs, and electronic packaging applications.
Examples of tribological applications include cylinder sleeves in engines, piston-recess
walls, and brake discs/pads (Suresh et al. 1993 ; Clyne and Withers 1995 ; Deuis et al.
1 997 ; Surappa 2 003 ).
Although such MMCs have been proposed/used for several applications, it should
be noted that their low ductility along with their poor machinability and weldability
has restricted its complete use. The low ductility is caused by the poor interfacial
characteristics between the reinforcement and matrix. Due to this drawback, they
exhibit low fracture toughness. Further, under tribological conditions, the brittleness
and hardness of these materials can cause damage to the counterfaces.