Transactions of Nonferrous Metals Society of China The Chinese Journal of Nonferrous Metals

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中国有色金属学报(英文版)

Transactions of Nonferrous Metals Society of China

Vol. 25    No. 2    February 2015

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Effect of multi-step slow shot speed on microstructure of vacuum die cast AZ91D magnesium alloy
Qing-liang WANG1,2, Shou-mei XIONG1,2

1. School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China;
2. State Key Laboratory of Automobile Safety and Energy, Tsinghua University, Beijing 100084, China

Abstract: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.

 

Key words: magnesium alloy; vacuum die casting; slow shot speed; gas porosity; externally solidified crystal

ISSN 1004-0609
CN 43-1238/TG
CODEN: ZYJXFK

ISSN 1003-6326
CN 43-1239/TG
CODEN: TNMCEW

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