Effect of solution heat treatment on microstructure and damage accumulation in cast Al-Cu alloys

The influence of solution treatment time on the microstructure of three cast Al-Cu alloys is investigated in terms of the effect on damage accumulation during tensile deformation at room temperature. The microstructure of the alloys is formed by an age hardenable α-Al matrix and interdendritic aluminides whose volume fraction and interconnectivity depends on the chemical composition and solution treatment time as revealed by 2D and 3D investigations. The damage accumulation process during tensile deformation is investigated in situ by synchrotron microtomography. Aluminides oriented perpendicularly to the load direction play a decisive role in damage formation and accumulation in the form of microcracks for all studied alloys and conditions. However, highly interconnected aluminides promote rapid crack propagation within these networks, indicating that the concentration of Cu should be kept <5 wt% and a solution heat treatment of 4 h at 530 °C should be applied to increase ductility of these cast alloys.