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采用金属型重力铸造工艺制备了Mg-Gd-Y-Zn-Zr耐热稀土镁合金发动机活塞,对充型和凝固过程中出现的各种缺陷进行分析,通过对成形工艺的改进消除了缺陷。结果表明,增大浇道的截面积,可以减少活塞的裙部、销孔和补缩冒口产生的浇不足缺陷;增加活塞销孔处壁厚,同时提高模具预热温度至250℃,可以减少活塞销孔处及裙部冷隔缺陷;去除浇道附近的补缩冒口,可以减少夹渣及冷隔缺陷的产生。铸态Mg-Gd-Y-Zn-Zr合金活塞本体组织中大量的第二相分布于晶界处,经过T6处理后部分固溶到基体中,使T6处理后活塞裙部硬度(HV)可达到158。
The piston of Mg-Gd-Y-Zn-Zr heat-resistant rare earth magnesium alloy engine was prepared by metal gravimetric casting process. Various defects occurred during filling and solidification process were analyzed. The defects were eliminated by the improvement of the forming process. The results show that increasing the cross-sectional area of the sprue can reduce the shortage of pouring caused by the skirt, the pin hole and the refueling riser of the piston; increasing the wall thickness of the piston pin hole and increasing the preheating temperature of the mold up to 250 ° C., Reduce the piston pin hole and the skirt cold septal defect; remove the runner near the feeder riser, can reduce the slag and cold septal defect. A large number of second phases in the as-cast Mg-Gd-Y-Zn-Zr alloy were distributed at the grain boundaries. After T6 treatment, some of the second phases dissolved in the matrix to make the hardness of the skirt skirt (HV) Reached 158.