镁合金汽车轮毂预制坯超塑成形研究

Study on superplastic forming of preformed blank for magnesium alloy wheel

研究了铸态AZ80A镁合金汽车轮毂预制坯的超塑成形,通过实验验证了该合金超塑性成形的最佳工艺参数为:成形温度410℃、应变速率0.01 s-1;在选定成形参数的基础上制订了超塑成形工艺,等温挤压成形出合格的汽车轮毂预制坯试样;通过对轮毂预制坯成形前后的微观组织的对比分析发现,在预制坯成形过程中AZ80A镁合金发生了动态再结晶,形状不规则的粗大铸态晶粒通过挤压成形变成了晶粒细小的等轴晶,枝晶状的β相被破碎,沿轴向等轴晶呈带状分布,形成了纤维织构。通过试样检测发现,等温成形轮毂预制坯的综合力学性能良好,特别是轴向力学性能更为突出,这是因为成形后的晶粒细化和纤维织构形成。

The superplastic forming of preformed blank for casting AZ80A magnesium alloy wheel was studied, and the optimal parameters of superplatic forming for this alloy were selected based on the tests. The forming temperature is 410℃, and the strain rate is 0. 01 s-i. Superplastic forming process was decided based on these parameters. The preformed blank of magnesium alloy wheel was made through i- sothermal extrusion technology. The microstructures of preformed blank wheel before and after forming were compared. The results show that the dynamic recrystallization happens during the preformed blank forming, the tiny isometric grains are obtained from big irregular casting ones through extrusion, the dendritic β phase is crushed, and along the axial direction the grains are in zonal distribution and fiber structure is formed. The synthesized mechanical properties of preformed blank of isothermal extruded wheel are excellent, especially the axial one is outstanding, which dues to the occuring of grain refinement and fiber structure caused by superplastic forming.