触变模锻成形工艺对镁合金成形件力学性能的影响

采用半固态等温热处理法、近液相线模锻法和等通道角挤压法制备AZ91D—Y镁合金半固态坯料。分别将3种状态的坯料加热到半固态温度区间进行二次重熔后，进行了触变模锻成形。结果表明，在半固态温度为560℃，模锻压力为200MPa的条件下，半固态等温热处理法、近液相线模锻法和等通道角挤压法制备坯料分别保温30，20，15min后触变模锻获得最佳力学性能；随着坯料加热温度的升高，触变模锻成形件力学性能呈现先上升后下降的趋势；增加成形压力有利于触变模锻成形件力学性能的提高；在相同成形条件下，等通道角挤压法制备坯料触变模锻后的力学性能最好，近液相线模锻法次之，半固态等温热处理法较差。

Effect of Thixoforging on Mechanical Properties of Magnesium Alloy Parts

Semi-solid thermal transformation, near-liquidus forging and equal channel angular extrusion （ECAE） were used to prepare AZ91D-Y magnesium alloy sembsolid billets. The semi-solid billets prepared by three routes mentioned above were reheated to semi-solid temperature range before thixoforging. Furthermore, the tensile mechanical properties of the parts thixoforged from starting material produced by three routes were examined at room temperature. The results show that when the preheating temperature of billet is 560 ℃ and applied pressure is 200 MPa, the isothermal holding times of obtaining best mechanical properties are 30 rain for the billet prepared by semi-solid thermal transformation, 20 min for the billet prepared by near-liquidus forging and 15 min for the billet prepared by ECAE. The mechanical properties of thixoforged parts increase initially then decrease with increasing reheating temperature. Moreover, the increase of pressure was favorable for the improvement of mechanical properties of thixoforged parts. Under the same conditions the mechanical properties of thixoforged parts prepared by equal channel angular extrusion are first, those prepared by near-liquidus forging are second and those prepared by semi solid thermal transformation are third.