Due to its excellent comprehensive performances, Al-Si-Mg alloy i widely used in automotive, transportation and other fields. In this work, tensile performances and fracture behavior of Al-Si-Mg alloy modified by dilute Sc and Sr elements (Al-7.12Si-0.36Mg-0.2Sc-0.005Sr) were investigated at the temperature of -60-200 °C for the first time, aiming to obtain a satisfactory thermal stability within a certain temperature range. The results showed that the new designed Al-Si-Mg alloy possessed a completely stable yield strength and a higher-level elongation under the present conditions. Fracture morphology analysis, fracture profile observation and strengthening mechanism analysis were applied to elucidate the evolution mechanisms of yield strength and elongation of the alloy. The fracture modes were significantly distinct in different temperature sections, and the reasons were discussed. In addition, the interaction among the nano precipitate phase particles, the deformation substructure and the dislocations were responsible for the thermal stability of the alloy within a certain temperature range.
Keywords: Al-Si-Mg alloy; heat treatment; mechanical performance; precipitation behavior.