Microstructure and Stress Variation of Semisolid 7A04 Alloy during Isothermal Compression

Abstract

The microstructure and stress variation of semisolid 7A04 alloy have been studied through unconstrictive isothermal compressing test. The results show that the relationships between true stress and true strain at different deformation temperatures and strain rates are the same, and the peak stress in the curve of true stress and true strain mainly depends on deformation temperature and strain rate. Analysis on the microstructure of compressive specimen demonstrates that segregation of liquid-solid phase is mainly affected by strain rate and deformation temperature. There are mainly two kinds of flow in liquid phase: either from the region with relatively large hydrostatic compressive stress to the region with relatively small hydrostatic compressive stress or from the grain boundaries perpendicular to the compressive axis to the grain boundaries with a certain directional angle to the compressive direction. Based on the above results, the microstructure and stress variation mainly depend on deformation temperature, strain rate and stress state.