Deformation Behavior of Spray Deposited 2014 Al-SiCP Composites

Abstract

Particle reinforced metal matrix composites have shown tremendous potential as an important candidate for structural components in automotive, aerospace and armour applications. However, due to limiting elastic deformation of rigid ceramic particles in the metal matrix as against dual phase alloys, the primary and secondary processing of such composites become a challenge. Therefore, a study of flow behavior of composites is of paramount necessity in determining a stable workability window of temperature and strain rate. The flow behavior of composites depends upon the applied temperature, strain and strain rate. In addition, the volume fraction, particle size, interfacial reactions and distribution of particles in the matrix play an important role. In contrast to the conventional stir casting route, spray deposition process gives rise to uniform distribution of particles along with moderate interfacial reactions. Therefore, in the present investigation, 2014 Al-SiCP composites were produced by spray deposition so as to reduce the interfacial reactions and obtain uniform distribution of SiCP particulates. The variation of particle size and volume fraction was in the range of 17, 30 and 58 μm and 5, 8.5 and 11 vol.%, respectively. The spray formed samples were tested for their compressive flow behavior at strain rates of 0.01, 0.1 and 1.0 s-1 and at the temperatures of 150, 300 and 450C. The porosity content were measured before and after deformation so as to ascertain local void formation in the samples at different strain rates and true strain conditions. The strain rate sensitivity (m) and the activation energy (Q) for deformation were calculated for different volume fractions and particle sizes. The results showed a decrease in m with increasing volume fraction for all the particle sizes. On the other hand, the value of m was observed to increase up to 30 μm particle size and then remains constant. The variation of m of composites, irrespective of particle size and content, showed that m increases up to a true strain of 0.3-0.4 and then decreases thereafter, showing different mechanisms of deformation at high strain. The activation energy for deformation decreases with particle size. The volume fraction also leads to lowering in activation energy, however, this effect is more pronounced at higher strain. This behavior of the composites has been discussed in light of microstructural observations and the void formation during deformation.