Effect of thixoforming and precipitation hardening on microstructure and mechanical properties of Al-10.5Si–3Cu-0.2Mg alloy produced by strain induced melt activation process

Abstract

The effects of the thixoforming and the precipitation hardening heat treatment on the microstructure and mechanical properties of Al-10.5Si–3Cu-0.2Mg alloy produced by the strain-induced melt activation (SIMA) process have been investigated. According to previous researches of authors, new introduced alloy has superior mechanical properties in addition to good response to aging process compared with the casting aluminum alloys. The results of the image analysis showed that by increasing the deformation from 10% to 20% and the time of semi-solid heat treatment from 10 to 20 min, the best globular structure of α(Al) grains with the grain size and shape factor of 65 μm and 0.81 were obtained at 15 min for 20% pre-deformation, respectively. The thixoforming process increased the ultimate tensile strength of the alloy about 29%, the yield strength about 37% and the elongation about 6%, compared to the as cast condition. The 20% pre-deformed sample experienced precipitation hardening heat treatment in addition to thixoforming had the best mechanical properties having UTS, YS, elongation and hardness of 423 MPa, 331 MPa, 4.41%, and 144.24 BHN, respectively. Thixoforming plus precipitation hardening is an effective procedure to produce a particular microstructure in Al–Si–Cu–Mg system exhibiting the excellent castability and high mechanical properties.