Optimization of Heat Treatment Parameters of AlSi7Mg Alloy

Constantly growing requirements concerning the quality of poured machinery components give rise to the need to find new solutions to improve their mechanical and technological properties, considering economic and ecological aspects resulting from energy consumption of the casting and heat treatment processes. This study presents the investigation of the effect of heat treatment on mechanical properties (tensile strength R, elongation A₅, hardness HBW) of the AlSi7Mg alloy without modification and modified with strontium. Obtained results allowed us to determine T6 heat treatment parameters associated with the improvement of mechanical properties of the alloy with simultaneous limitation of duration of solutioning and aging treatments. The maximum increase in R was 67%, and 55% in the case of HBW, with a slight decrease in elongation (approx. 10%) in relation to an alloy not subjected to heat treatment in the adopted scope of tests for the total time of heat treatment of 4-6 h. The increase in elongation of up to 250% requires aging at a temperature exceeding 300 °C, which also causes a decrease in durability and hardness by 20%. Modification of the alloy using strontium before heat treatment facilitates the process of fragmentation and balling of silicone precipitates.