Grain nucleation and formation in Mg-Zr alloys
Grain nucleation and formation in Mg-Zr alloys
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DOI：
10.1179/136404609x367885
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发表时间：
2009-08-01
影响因子：
1.4
通讯作者：
StJohn, D. H.
中科院分区：
文献类型：
--
作者：
Qian, Ma;StJohn, D. H.
锆是迄今为止发现的最有效的镁成核剂。这项工作报告了锆孕育镁熔体中的晶粒成核和形成特征。研究发现，镁晶粒的形核发生在两种类型的锆成核剂上，其中第一种类型较小且圆形，表明它们是通过沉淀形成的，而另一种类型较大且形状不规则，类似于未溶解的颗粒。在相似的冷却条件下，成核后镁晕结构的后续生长可以呈球形或树枝状生长，但在孕育良好的条件下，它们通常呈球形生长。因此，实现高水平的溶解Zr含量不仅对于成核过程至关重要，而且对于控制晕圈结构的后续生长形态也很重要。成核过程可以通过吸附机理来理解。
Zirconium is the most potent nucleant discovered to date for magnesium. This work reports the grain nucleation and formation characteristics in zirconium-inoculated magnesium melts. It was found that nucleation of magnesium grains occurred on two types of zirconium nucleants, where the first type were small and round, suggesting that they were formed by precipitation, and the other type were larger and irregularly shaped, similar to undissolved particles. Subsequent growth of the magnesium halo structures after nucleation could occur either spherically or dendritically under similar cooling conditions but under well-inoculated conditions they grew spherically in general. Hence, achieving a high level of dissolved Zr content is not only essential to the nucleation process but also important for control of the subsequent growth morphologies of the halo structures. The nucleation process can be understood by an adsorption mechanism.