10-11-2012, 04:07 PM
Mechanical and Tribological Behavior of Particulate Reinforced Aluminum
Metal Matrix Composites – a review
Mechanical and Tribological.pdf (Size: 343.82 KB / Downloads: 87)
ABSTRACT
Aluminum Metal Matrix Composites (MMCs) sought over other conventional materials in the
field of aerospace, automotive and marine applications owing to their excellent improved
properties. These materials are of much interest to the researchers from few decades. These
composites initially replaced Cast Iron and Bronze alloys but owing to their poor wear and
seizure resistance, they were subjected to many experiments and the wear behavior of these
composites were explored to a maximum extent and were reported by number of research
scholars for the past 25 years. In this paper an attempt has been made to consolidate some of the
aspects of mechanical and wear behavior of Al-MMCs and the prediction of the Mechanical and
Tribological properties of Aluminum MMCs.
INTRODUCTION
Metal Matrix Composites are being increasingly used in aerospace and automobile industries
owing to their enhanced properties such as elastic modulus, hardness, tensile strength at room
and elevated temperatures, wear resistance combined with significant weight savings over
unreinforced alloys [1-4]. The commonly used metallic matrices include Al, Mg, Ti, Cu and their
alloys. These alloys are preferred matrix materials for the production of MMCs. The
reinforcements being used are fibers, whiskers and particulates [5]. The advantages of particulate-reinforced composites over others are their formability with cost advantage [6].
Further, they are inherent with heat and wear resistant properties [7, 8]. For MMCs SiC, Al2O3
and Gr are widely used particulate reinforcements. The ceramic particulate reinforced
composites exhibit improved abrasion resistance [9]. They find applications as cylinder blocks,
pistons, piston insert rings, brake disks and calipers [10]. The strength of these composites is
proportional to the percentage volume and fineness of the reinforced particles [11]. These
ceramic particulate reinforced Al-alloy composites led to a new generation tailorable engineering
materials with improved specific properties [12, 13].
PROPERTIES OF COMPOSITE MATERIALS
From the nature and morphology of the composites, their behavior and properties can be
predicted and the factors such as intrinsic properties, structural arrangement and the interaction
between the constituents are of much importance. The intrinsic properties of constituents
determine the general order of properties that the composite will display. The interaction of
constituents results in a new set of properties. The shape and size of the individual constituents,
their structural arrangement and distribution and the relative amount of each contribute to the
overall performance of the composite. The factors that determine properties of composites are
volume fraction, microstructure, homogeneity and isotropy of the system and these are strongly
influenced by proportions and properties of the matrix and the reinforcement. The properties
such as the Young’s modulus, shear modulus, Poisson’s ratio, coefficient of friction and
coefficient of thermal expansion are predicted in terms of the properties and concentration and
the most commonly used approach is based on the assumption that each phase component is
subjected to either iso-stress or iso-strain condition.
Mechanical Properties
Hardness
The resistance to indentation or scratch is termed as hardness. Among various instruments for
measurement of hardness, Brinell’s, Rockwell’s and Vicker’s hardness testers are significant.
Theoretically, the rule of mixture of the type