Tension-compression mechanical behavior and corresponding microstructure evolution of cast A356-T6 aluminum alloy

Abstract

It is crucial to clarify the intrinsic deformation and damage behaviors of casting materials under different loading conditions for establishing the material damage model and accurately predicting the security performance of cast components. In this study, uniaxial tensile and compressive tests were performed to investigate the complete mechanical behavior of cast A356-T6 aluminum alloy at room temperature, and the corresponding microstructure evolution were analyzed. The tensile and compressive specimens were prepared at porosity-free locations on a low pressure die cast A356 wheel subjected to T6 heat treatment to avoid premature fracture caused by initial cast pores. The results show that negligible asymmetry in yielding and hardening behaviors is observed between tension and compression, but obvious differences in ductility exhibit. Specifically, the elongation for tension is limited to 15%, but reaches over a strain of 1.2 for compression. Additionally, microcracks during tension are prone to be initiated at the interface between Si and Al matrix, which mainly propagates in the Al dendrites, and finally leads to the fracture. While the dominant strain accommodated mechanism shifts with strain levels in compression. It evolves from the incipient plastic deformation inside grains at initial strain stage to the sliding of fragmented dendrite assisted by eutectic silicon particles at later stage, which may be the main reason for the superior ductility during compression.