通过近液相线‘铸造’的方法得到了细晶组织.采用感应加热方式将熔体处理至近液相线温度附近指定温度,然后让熔体直接在坩埚中炉冷.在具有一定形核过冷度的坩埚中得到了细晶组织并探索了晶粒细化的机制.可以将过冷熔体的凝固过程分为2个阶段:非平衡凝固阶段;近平衡凝固阶段.与近平衡凝固阶段相比,球形晶粒扰动发展的临界半径Rc在非平衡凝固阶段急剧减小.在非平衡凝固阶段,晶粒更倾向于以枝晶方式长大,晶粒的增殖通过枝晶的熔断产生并且最终的晶粒密度由该过程决定.在近平衡凝固阶段Rc急剧增大.Rc的增大与晶粒增殖阶段所确定大的核心密度导致凝固在球形晶粒扰动发展之前终止.因此,最终得到粒状晶粒形态.
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