Abstract:The hypoeutectic Al-Si alloy billet with non-dendrite was reheated to meet the needs of the semi-solid thixoforming microstructure by four kinds of reheating power, achieving the same final temperature of 851 K. Subsequently, under the same condition of thixoforming, the microstructure, surface hardness and tensile properties were observed. Afterwards, quantitative analysis was made for the microstructures of the reheated semi-solid of billet and the thixoforming parts. The results show that when the induction reheating power is 90 kW, the average grain size of the semi-solid billet is the minimum, the microstructures of the thixoforming samples also are the finest, and the mechanical properties of the relevant thixoforming samples are the best. Furthermore, after studying on the relationship between the microstructures of the semi-solid billet of aluminum alloy and the mechanical properties of the thixoforming samples, the reverse design of microstructure is primarily achieved. Finally, the effectiveness of the reverse design for semi-solid microstructure is confirmed by an actual automobile part with complex shape.

Key words: Al-Si alloy; semi-solid; microstructure; reheating; reverse design