A study on deformation behaviour of Cu- Al2O3 metal matrix composite with the variation of size and volume fraction of reinforcement particle

Metal matrix composites are revolutionary materials of future which have endowed the material industry with excellent properties which can be tailored in context to desired applications and requirements. The Cu-Al2O3 metal matrix composites apart from resisting softening at high temperatures have applications such as spot welding electrodes, lead frames commutators for starting helicopters, catalysts with a high degree of conversion, coatings with low porosity and high adhesion. In the present investigation Cu–Al2O3 micro- and nanocomposites with different volume fractions of alumina (5, 10, 15 and 20 vol. %) were fabricated by powder metallurgy route. The specimens were sintered at different temperatures (850◦C, 900◦C and 1000◦C temperature) to study the effect of sintering temperature on physical and mechanical properties of the composites. These micro- and nano-composites have been characterized using X-Ray diffraction, scanning electron microscopy and atomic force microscopy followed by density, microhardness and wear measurements. Deformation mechanism dominated by dislocation motion has been emphasized comprehensively and critically by changing the particle size and volume fraction of the reinforcement. The mismatch in several physical and mechanical attributes of the matrix and reinforcement entities give rise to misfit strain, thermal misfit, lattice parameter misfit, elastic inhomogeneity misfit. Our investigation focuses comprehensively on thermal misfit in metal matrix composites. The differential elastic modulus of reinforcement Al2O3 particle and matrix copper leads to development of misfit strain. It restricts the mobility of dislocation in the matrix leading to strengthening contribution of misfit hardening which is expressed as Where τ is the misfit strain hardening, G is the shear modulus, is the misfit strain, r is the radius of the particle, f is the volume fraction of the reinforcement. The flexural and compression tests were carried out to investigate the mechanical behavior of MMCs. The thermal mismatch of both entities (matrix and reinforcement) plays a vital role in the thermo-mechanical reliability of the composite. Thermal misfit dislocations at the interface results in generation of strain field at the particle-matrix interface. The amount of geometrically-necessary dislocation density generated in the matrix- reinforced particle interface can express as Where ρg dislocation density, ∆α is the difference in thermal expansion coefficient, ∆T is the change in temperature; f is the volume fraction of the reinforcement √2 rp is the dislocation loop radius. The specimens of Cu – 5 % Al2O3 having particle size (10 µm,