Investigation On Microstructure And Mechanical Property Of Semi-solid Forming A390 Aluminum Alloy

A390 aluminum alloy belong to hypereutectic Al-Si alloy, which has the excellent properties such as good mechanics performance, wear resistance, corrosion resistance, volume stability and castability. Because of its low density, aluminum alloy can substitute steel for automobile, which can greatly reduce the weight of the vehicle, contributing to decreasing the demand for the crude oil. So the use efficiency of Al-Si alloy in automobile of western developed country is increasing quickly. To decrease the dependence on crude oil in foreign countries, especially in the energy crisis, our country pay high attention to the use of aluminum alloy.For the moulding mode, it’s better to reduce amount of machining, which helps to decrease material waste. Semi-solid forming is a near net shaping technology, which is a moulding mode between liquid and solid. It has good liquidity and solid stabilization. So it’s a moulding mode of the near net shaping technology of less defect, good property, high productivity, less pollution. The combination of hypereutectic Al-Si alloy and semi-solid forming is good for production of car parts of good property, less amount of machining and complex shape.In the paper, effect of reheating process, heat treatment and modification process on micro structure and mechanical property of hypereutectic A390 aluminum alloy were studied and analyzed, which were based on the theory formulation. Through analysis of every process, we made the best craft to produce hypereutectic A390 aluminum alloy.The result shows that reheating of A390 aluminum alloy experiences two processes of grain combination and Ostwald growing, which results in the growing of microstructures. If we want to control microstructure, the reheating power and temperature should be strict controlled. At 7.3kw and 540℃, the microstructures were fine and homogeneous. At the same time, mechanical property and productivity are best.Through T6 heating on A390 aluminum alloy, at heating on 500℃ in 8 hours, the secondary phase of richer copper between the grains would melt into the substrate. If the heating temperature exceeds 500℃, the A390 aluminum alloy would be overburning. Strengthening is the result of coordination of fine-grain strengthening, solution strengthening, dispersion strengthening. The heating on 500℃ in 8 hours is the best heating temperature and time.Through the study on the modificator of Sr, we found that Sr can only modify eutectic silicon. But the aluminum alloy we used contains P modificator. Sr has bad influence on the effective of P,modificator, which result in the coarsening of primary silicon. Sr is a long-effective modificator. At reheating process, Sr can also control the growing up of eutectic silicon. Because of its bad influence on P modificator, we should consider seriously the amout of Sr modificator.