Effect of heat treatment on microstructure and tensile properties of A356 alloys

摘要

Two heat treatments of A356 alloys with combined addition of rare earth and strontium were conducted. T6 treatment is a long time treatment (solution at 535 degrees C for 4 h + aging at 150 degrees C for 15 h). The other treatment is a short time treatment (solution at 550 degrees C for 2 h + aging at 170 degrees C for 2 h). The effects of heat treatment on microstructure and tensile properties of the Al-7%Si-0.3%Mg alloys were investigated by optical microscopy, scanning electronic microscopy and tension test. It is found that a 2 h solution at 550 degrees C is sufficient to make homogenization and saturation of magnesium and silicon in alpha(Al) phase, spheroid of eutectic Si phase. Followed by solution, a 2 h artificial aging at 170 degrees C is almost enough to produce hardening precipitates. Those samples treated with T6 achieve the maximum tensile strength and fracture elongation. With short time treatment (ST), samples can reach 90% of the maximum yield strength, 95% of the maximum strength, and 80% of the maximum elongation.

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