Effect of deviatoric plastic strain on the mechanical behaviour of composite powder compacts with large amount of hard phase

The effect of increasing amounts of deviatoric plastic strain on the mechanical behaviour of powder composite compacts is investigated. The study focuses on a highly charged composite of soft Aluminium particles with hard Nickel based super-alloy particles. Three mechanical tests, imposing different stress states, are carried out at various temperatures on powder compacts that have been submitted to increasing amount of deviatoric plastic strain. These tests are used to gather information on the alterations that such deviatoric strains cause on the powder compact mechanical response. It is shown that the ductility and the yield stress of the powder compacts increase with increasing amounts of cumulated plastic strain. The particulate nature of the compact fades, but some aspects of the mechanical behaviour (macroscopic rate dependence in particular) are still characteristic of the original particulate material even after significant amount of accumulated deviatoric strain. Microstructural observations are carried out to provide a reasonable scenario for the mechanisms responsible of the alterations that deviatoric strains bring. C 2005 Springer Science + Business Media, Inc.