On the effect of macroporosity on the tensile properties of the Al-7%Si-0.4%Mg casting alloy

Abstract

The purpose of the present note is to put forward a simple model which predicts the effect of porosity on the tensile behavior of the Al-7%Si-0.4%Mg alloy in the T-6 condition. In order to validate the calculations, the predictions of the model are contrasted against the experimental results of Surappa et al. for the same material. On the assumption that localized porosity in a tensile sample concentrates the strain due to the reduce load bearing area, the rate of strain concentration can be described using existing models for the growth of plastic instabilities. By assuming that fracture occurs in the region of maximum strain at a given value of the local strain, the overall strain to fracture can be calculated for different levels of porosity. The procedure can be applied to calculate the effect of porosity on the fracture stress. The calculations indicate that even low levels of localized porosity may have a significant effect on both the tensile ductility and the tensile strength of the material. These predictions are in good agreement with published results for the casting alloy Al-7Si-0.4Mg T-6.