Artificial ageing of Al-Si-Cu-Mg casting alloys

► Tensile testing of three Al-Si-Cu-Mg alloys, 3 SDAS, 2 ageing temperatures. ► YS after ageing is weakly dependent on the coarseness of the microstructure. ► The elongation of the Al-8Si-3Cu-0.5Mg with SDAS 10 μm recover on overageing. ► The Q index Q = YS + Kɛ can compare different Al-Si-Mg alloys but not Al-Si-Cu-Mg alloys. ► Al-Si-Mg alloys are preferred over Al-Si-Cu-Mg alloys for YS below about 300 MPa.