WEA331-xSi合金普通凝固的组织特征

Microstructure of Conventional Solidified WEA331-xSi Alloys

研究了WEA331-x Si(x=0、0.5、1.0、1.5和2.0)的凝固组织特征。结果表明,WEA331合金由α-Mg、Mg_(24)Y_5、Mg_(12)Nd和Al_3Y相组成,粒状晶粒尺寸约为44.8μm。添加0.5%Si时,合金中出现呈团聚状分布的高温相YSi_2和Gd_5Si_3,其熔点分别为(1650±20)℃和1520℃,晶粒转变为由枝晶臂构成的晶粒,尺寸细化到23.4μm;Si含量为1.0%时,组织中除了原有相外还出现少量Mg_2Si,晶粒尺寸减小到19.7μm;Si含量超过1.5%时,合金中出现汉字状Mg_2Si和大块状Mg_2Si,晶粒再度转变为粒状晶,尺寸增大到超过31.6μm。从组织特征看,WEA331中添加1.0%Si时最有可能获得高性能高温合金。

The microstructure of WEA331-xSi（x=0, 0.5, 1.0, 1.5 and 2.0） alloys were investigated. The results show that the microstructure of WEA331 alloy is composed of α-Mg, Mg24Y5, Mg12Nd and Al3Y. The granular grain size of WEA331 is about 44.8 μm. When WEA331 is added with 0.5% Si, there are two new high temperature aggregation phases YSi2 and GdsSi3 distributed in matrix, whose melting points are （1650±20） ℃ and 1520 ℃ respectively. The microstructure is composed of dendrite ann grains and the grain size is refined to 23.4 μm. When the Si content is 1.0%, in addition to the original phase there also appears a small amount of Mg2Si, and the grain size is about 19.7 μm. When the content of Si exceeds 1.5%, the Chinese character shaped eutectic Mg2Si and the bulk Mg2Si appear in the alloy. The grains change into granular grains again, while the grain size increases to more than 31.6 μm. From the perspective of microstructure characteristics, the WEA331 alloy with 1.0% Si is most likely to obtain high performance at high temperature.