IMDEA–Materials Institute, Getafe Madrid, Spain
Received Date: August 14, 2013; Accepted Date: August 17, 2013; Published Date: August 20, 2013
Citation: Rahimian M (2013) Characterization of Particle Reinforced Metal Matrix Composite Processed by Powder Metallurgy. J Powder Metall Min 2: 111. doi: 10.4172/2168-9806.1000111
Copyright: © 2013 Rahimian M. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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Today, there is an increasing need worldwide for the advanced materials in order to obtain the desired properties. This is because a single material generally cannot meet the requirements of harsh engineering environments. That is why the need for composites with unique properties is growing every day. Metal matrix composites (MMC) are widely used in different industries because of their high mechanical properties and wear resistance. Aluminum matrix composites have made numerous applications in aerospace, automotive, military and electronic industry due to low density, high toughness and high corrosion resistance. The main drawback of Aluminum is its low wear resistance. This problem can be overcome by addition of ceramic particles. Addition of ceramic particles to aluminum matrix would improve the strength, hardness, wear resistance, and corrosion resistance of the matrix. Particle reinforcements are more favorable than fiber type, due to better control of microstructure and mechanical properties, by varying the size and the volume fraction of the reinforcement. Among the ceramic reinforcements, Al2O3 is favorable since it does not react with the matrix at high temperatures and does not create undesired phases.
Powder metallurgy is considered as a highly flexible technique in producing metal-matrix composites. An important advantage of this method is its low processing temperature compared to melting techniques. Therefore, interaction between the matrix and the reinforcement phases is prevented. On the other hand, good distribution of the reinforcing particles can be achieved. Another advantage of powder metallurgy technique is in its ability to manufacture near net shape product at low cost. Extrusion can be applied from the beginning of production or as a supplementary step after compaction.
Particle size and the amount of reinforcement have pronounced effects on the mechanical properties of composites. Hardness and wear resistance, of the composite is improved by proper addition of the reinforcement.
Since alumina is inherently harder than aluminum, its presence leads to a higher hardness in the composite, which can be analyzed by the rule of mixtures (Equation 1)
Hm, HC and Hr are the hardness of the matrix, composite and reinforcement respectively. fm and fr are the volume fraction of the matrix and reinforcement respectively.
In other words, the reduction of the size of alumina showed the same trend. Two opposing mechanisms take part in the overall hardness of Al-Al2O3 composites. Reinforcements increase the hardness value since they are inherently harder than the matrix. On the other hand, reduced densities have been reported under such circumstances due to lower compressibility of alumina.
Moreover, as the alumina particle size is reduced, according to Equation 2, more stress is required to allow the dislocations to pass the reinforcements; hence, higher hardness values are achieved.
τ0is the required stress of a dislocation to pass through a hard phase, G is the shear modulus of the material and b is the burgers vector of the dislocation.
In other words, with increasing Alumina amount in the composite, its wear resistance increases, too. The reason for this phenomenon is due to higher hardness of Alumina compared with that of pure Aluminum matrix. Therefore, according to the rule of mixtures, increasing the Alumina amount can justify the increase in the wear resistance.
As the Alumina particle size increases the composite’s wear rate decreases. The reason is the decrease in the surface roughness as the Al2O3 particle size increases.
Regarding composite materials and powder metallurgy method, high numbers of variations take part in the final characteristic of a composite. However, variations can be manipulated with powder metallurgy production technique to achieve the high quality specimen with required characteristics.--
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