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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。
Fine grain structure was obtained by casting near liquidus. Induction heating is used to treat the melt near the specified temperature near the liquidus temperature and then allow the melt to cool directly in the crucible. In a crucible with a certain degree of nucleation undercooling, a fine grain structure was obtained and the mechanism of grain refinement was explored. The process of solidification of subcooled melt can be divided into two stages: non-equilibrium solidification stage and near-equilibrium solidification stage. Compared with the near-equilibrium solidification stage, the critical radius Rc of the spheroidal grain disturbance decreases sharply during the non-equilibrium solidification stage. In the non-equilibrium solidification stage, the grains tend to grow in a dendritic manner, the growth of the grains is caused by the detonation of the dendrite and the final grain density is determined by the process. Rc rapidly increases during the near equilibrium phase of solidification. The increase of Rc and the core density determined by the stage of grain growth lead to the termination of solidification before the development of spherical grain disturbances. As a result, granular grain morphology is finally obtained.