Semi-solid microstructure evolution during reheating of aluminum A356 alloy deformed severely by ECAP

Semi-solid metal forming is a new developing technology that has some advantages in relation to other forming and casting technologies like high pressure die casting. This process contains three main steps: feedstock manufacturing, reheating and forming. Producing feedstocks with non-dendritic and spherical microstructure is one of the considerable factors in semi-solid forming. Feedstock manufacturing can be carried out with casting methods and solid-state methods. In solid-state processes like SIMA, remelting stage and related contamination is eliminated which is especially, useful for active metals. In this research, A1 (A356) has been used and in order to induce strains, equal channel angular pressing (ECAP) has been utilized. ECAP is one of the most effective and practical sever plastic deformation (SPD) methods to induce a great strain. In this study specimens were ECAPed for one to four passes to examine the effect of strain on the morphology and shape factor of reheated alloy. Conclusions indicate that with increase of strain, sphericity of particles increases, their size will decrease and sphericity takes place in less reheating time. (C) 2007 Elsevier B.V. All rights reserved.