Variability in the tensile properties of squeeze-cast Al-Si-Cu-Mg alloy

The variability in the tensile properties of Al-10%Si-2%Cu-0.4%Mg alloy was investigated in terms of the variation in load bearing capacity due to anisotropic fracture damage of Si-particle and fraction of micro-voids in the as-cast and T6-treat conditions. The area fraction of micro-voids was measured by quantitative analyses through SEM fractography on entire test specimens, and the aspect ratio of Si-particle was measured as a microstructural shape factor describing the anisotropic morphology of Si-particle. The UTS and elongation of the as-cast and T6-treat alloys can describe as power law relationship to the variation of effective internal void area which is the sum of the area fraction of micro-voids and additional increment by anisotropic fracture damage of Si-particle. The overall tensile properties of both alloys are depended practically on the high volume fraction and anisotropic damage of Si-particle, rather than the area fraction of micro-voids only. The defect susceptibility of as-cast and T6-treat alloys to the variation of effective internal void area has similar level, despite of a remarkable difference on anisotropic morphology of Si-particle between both alloys.