钇对Mg_2Si/AZ91D复合材料中Mg_2Si相变质的影响

Effect of Yttrium on Modification of Eutectic Mg_2Si Phase in Mg_2Si/AZ91D Composite

研究了不同含量的钇对Mg2Si/AZ91D复合材料中Mg2Si相形貌的影响。结果表明:Y对Mg2Si/AZ91D复合材料中共晶Mg2Si有明显的细化变质效果,合金液经0.8%Y变质后,共晶Mg2Si相由粗大的树枝状或汉字状转变为颗粒状。在1.2%添加范围内,随Y加入量的增加,对共晶Mg2Si相的细化变质效果增强,未出现过变质现象。固溶处理能使Mg2Si/AZ91D复合材料中枝状或汉字状Mg2Si发生部分溶解,并依靠原子扩散自发粒状化,Y的细化变质能促进Mg2Si相固溶处理时的粒状化。

The effects of yttrium content on the morphologies of eutectic Mg2Si phases in Mg2Si/AZ91D composite were investigated.The results show that yttrium can effectively modify the eutectic Mg2Si phases in Mg2Si/AZ91D composite.The morphologies of eutectic Mg2Si phases changes from coarse dendrites or Chinese script shape into fine polygonal shape with 0.8% yttrium addition.Over modification of the eutectic Mg2Si phases was not found when the content of yttrium increases to 1.2%.The modification mechanism should be associated with the enrichment of yttrium and their intermetallic compounds on the growth faces of the eutectic Mg2Si crystals.The coarse dendrites or chinese script could be dissolved partially and tended to be spheroidized during solution heat treatment due to the diffusion of Si atoms.Yttrium modification can promote the spheroidization of Mg2Si phases during solution treatment.