Cyclic deformation behavior of an overaged high-pressure die-cast aluminum alloy

The aim of this study is to identify the deformation behavior of a high-pressure die-cast Silafont (R)-36 aluminum alloy in an overaged T7 condition in relation to the significant microstructural changes caused by the overaging heat treatment. The T7 aluminum alloy exhibited a distinctive composite-like microstructure, consisting of coarser alpha-Al grains and larger spherical Si particles embedded in the matrix, in contrast to its as-cast and T4 counterparts. The softer alpha-Al matrix of the T7 alloy as revealed by the nanohardness and microhardness led to improved ductility and longer strain-controlled fatigue life at higher strain amplitudes, despite the lower strength. Cyclic stabilization was observed to be a salient feature of the T7 alloy, stemming from the equilibrium between cyclic hardening and cyclic softening. Strain-energy density-based model, by incorporating a material parameter called 'intrinsic fatigue toughness', could be used to predict the fatigue life of the alloy.