The Mechanical Response of an Al Alloy Reinforced with SiC

Abstract

This study investigated the role of Sic particles in the mechanical behaviour of a metal matrix composite (Al-SiC). Measurements of the development and magnitude of internal stresses were performed from Bauschinger experiments in the aluminum matrix A-356 reinforced with the Sic particles. The behavior of the Al matrix itself was also analyzed. The level of internal stresses in the particulate reinforced composite was found to saturate after 0.9% plastic strain and after 1.3% in the unreinforced matrix. The initial development of the unrelaxed internal stresses was analyzed using both microscopic and macroscopic models of the load-bearing role of the Sic particles. The Sic particles were found to have little influence on the plastic flow of the composite beyond the initial plastic deformation as the size and distribution of the Sic is very non-uniform. The effect of the Sic phase was compared to continuous fibers embedded in a metallic matrix. A model system of pure copper reinforced with continuous tungsten fibers was used for this purpose. The effect of the internal stresses on the dimensional stability of the particulate reinforced and the unreinforced matrix was also investigated. The generation of dislocations arising from the thermal cycling of those materials was also analyzed by reference to the increase in flow stress observed after thermal cycling and from a model based on dislocations production due to the difference in coefficient of thermal expansion of the phases.