深过冷Fe-30Co合金中亚稳相形成与组织演化

METASTABLE PHASE FORMAION AND MICROSTRUC-TURE EVOLUTION IN UNDERCOOLED Fe-30Co ALLOY

采用熔融玻璃净化法，在Ｆｅ－３０Ｃｏ（原子分数，％，下同）合金中获得了３０８Ｋ的过冷度，借助光学显微镜和透射电子显微镜观察了过冷度与组织演化的关系以及ｂｃｃ亚稳相的微观结构确定了在深过冷条件下，Ｆｅ－３０Ｃｏ合金形成亚稳相的临界过冷度，从过冷熔体枝晶生长的角度分析了ｂｃｃ亚稳相和ｆｃｃ稳定相的生长速度和过冷度的关系。

The maximum undercooling of 308 K was achieved in Fe-30Co alloy by purifying the alloyin the molten glass. The microstructures of the alloy solidified at selected undercoolings were investigatedto reveal the evolution process and the microstructure of primary metastable bee phase was also observedby TEM technique. The critical undercooling for the formation of metastable bee phase from undercooledFe-30Co melt was determined by observing the microstructure differences. Based on the classical BCTmodel, the crystal growth velocities of bee and fee phases from undercooled melt were also calculated asa function of undercooling. The critical condition under which the metastable phase was formed and thefactors that governed the formation of the phase were also analyzed from the view of thermodynamics.