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The mechanical properties optimization of Al-6Si-0.5 Mg-2Cu-2Ni alloy by precipitation hardening

Abstract The effect of artificial ageing on the hardness, microstructure, tensile strength, ductility and impact toughness of Al-6Si-0.5 Mg-2Cu-2Ni alloy was investigated. The alloy was homogenized for 24 h at 500 °C, solution treated for 2 h at 540 °C and aged for 1 h at various temperatures in the range 20–300 °C. The isochronal and isothermal ageing were monitored by hardness measurements. Tensile properties of the aged alloy were determined by tension tests at a constant strain rate of 10−3/s using an Instron tensile testing machine. The impact toughness reached its minimum at the peak hardness or peak strength. The microstructure and fracture surface were examined under a scanning electron microscope, and corelation between the mechanical properties and microstructures were investigated. The results show the optimum mechanical properties could be achieved by artificial ageing for 1 h at 225 °C.