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研究了不同混合稀土添加量对AZ91D合金晶粒细化的影响。试验结果表明混合稀土对AZ91D合金有明显的细化效果。当混合稀土的添加量为 0 .0 5 % (质量分数 )时 ,混合稀土中的Ce ,Nd和Pr等在未形成Al RE化合物之前 ,大部分以质点的形式弥散分布在AZ91D合金熔体中 ,可能起到非均匀形核的作用 ;随着混合稀土添加量的增多 ,RE优先与Al生成Al RE化合物 ,这些化合物大部分偏聚在晶界上 ,阻碍了晶粒的长大 ,从而细化了晶粒。
The effect of different RE content on the grain refinement of AZ91D alloy was studied. The experimental results show that the mixed rare earth AZ91D alloy has obvious refining effect. When the mixed rare earth is added in an amount of 0.05% (mass fraction), most of the Ce, Nd and Pr in the mixed rare earth are dispersed in the melt of the AZ91D alloy in the form of particles before the Al RE compound is formed , Which may play the role of inhomogeneous nucleation. With the increase of RE content, RE preferentially forms Al RE compound with Al, and most of these compounds are segregated on the grain boundary, which hinders the grain growth and thus fine The grain.