Effect of route BC-ECAP on microstructural evolution and mechanical properties of Al–Si–Cu alloy

Abstract

In this study, the microstructure, tensile properties, and the fracture behavior of hypereutectic A390 aluminum alloy produced by route BC of equal channel angular pressing (ECAP) were investigated. Microstructural observations showed that the microstructure of the A390 alloy was considerably improved by the ECAP. After the fourth pass, most of the primary silicon particles (PSPs) and coarse acicular eutectic silicon particles (ESPs) were broken, and the α-Al was refined. The ultimate tensile strength (UTS) of ECAPed specimens after 1 pass, 2 passes, 3 passes, and 4 passes was increased by 28%, 59%, 30%, and 61%, and the fracture strain was improved by 52%, 54%, 106%, and 93%, respectively. The fractography results revealed that the fracture mechanism turned to mixed rupture which is characterized by cleavage in the PSPs and dimples in the Al matrix. Finally, results showed that route A on modifying of microstructure and improvement of the tensile properties is more effective than route BC. This difference could be explained by the redundant strain between each pass and cyclic restoration in every 4 passes of route BC.