Effect of multi-step slow shot speed on microstructure of vacuum die cast AZ91D magnesium alloy  

分段慢压射速度对AZ91D镁合金真空压铸件组织的影响（英文）

作　　者：王青亮[1,2] 熊守美[1,2] 

机构地区：[1]清华大学材料学院,北京100084 [2]清华大学汽车安全与节能国家重点实验室,北京100084

出　　处：《Transactions of Nonferrous Metals Society of China》2015年第2期375-380,共6页中国有色金属学报（英文版）

基　　金：Project(51275269)supported by the National Natural Science Foundation of China;Project(20121087918)supported by the Independent Research Program,China;Project(2012ZX04012011)supported by the National Science and Technology Major Project of the Ministry of Science and Technology of China;Project(2013M540936)supported by Postdoctoral Science Foundation of China

摘　　要：Two multi-step （two-step and three-step） slow shot speeds were used in the vacuum die casting process of AZ91D magnesium alloy. The vacuum pressure variation in the die cavity before mold filling was monitored by using a pressure sensor. The microstructures of the produced castings were analyzed with optical microscope and image analysis software. The experimental results demonstrate that, the vacuum pressure in the die cavity at the beginning of mold filling is significantly reduced by using three-step slow shot speed, resulting in a low gas porosity level in the produced castings. At an appropriate multi-step slow shot speed, the dwell time of the liquid metal in the shot sleeve before mold filling can be reduced and the flow of the liquid metal in the shot sleeve at the later stage of the slow shot process can be restrained, which cause a low externally solidified crystal content in the produced castings.在AZ91D镁合金真空压铸过程中使用2种分段慢压射速度(两段和三段)。在充型之前型腔内真空压力变化情况通过真空传感器进行监测。压铸件组织通过光学显微镜和图像分析软件进行分析。结果表明,采用三段慢压射速度时充型时刻型腔真空压力明显降低,导致所得压铸件中气孔含量很低。通过恰当选用分段慢压射速度,在充型之前金属液在压室中的停留时间可缩短,在慢压射过程后期阶段金属液在压室中的流动也将受到抑制,这些因素可导致所得压铸件中压室预结晶组织含量较低。

关 键 词：magnesium alloy vacuum die casting slow shot speed gas porosity externally solidified crystal 

分 类 号：TG249.2[金属学及工艺—铸造]