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采用玻璃熔体净化与循环过热相结合的深过冷凝固技术实现了Co_(80)Pd_(20)合金的深过冷,获得了高达415K的最大过冷度.采用OM观察了不同过冷度下凝固合金的微观组织,分析了枝晶形成的过冷度区间及过冷度对枝晶形貌的影响.运用BCT模型对深过冷凝固Co_(80)Pd_(20)中的枝晶生长进行了理论分析,获得了深过冷凝固过程中的枝晶生长速率、枝晶尖端半径、枝晶尖端溶质浓度及枝晶尖端过冷度组成与过冷度之间的关系,详尽探讨了过冷熔体中的枝晶生长方式.借助EDS分析近似测定了凝固过程中枝晶尖端液相溶质浓度,与BCT模型预测结果符合较好,表明BCT模型可成功运用于描述Co_(80)Pd_(20)合金中的枝晶生长.
The deep undercooling of Co_ (80) Pd_ (20) alloy was achieved by deepcooling solidification combined with the purification of glass melt and overheating cycle, and the maximum undercooling of up to 415 K was obtained. And the effect of undercooling degree and supercooling degree on dendritic morphology was analyzed.The BCT model was used to study the dendrite growth in Co_ (80) Pd_ (20) The relationship between the dendrite growth rate, the dendrite tip radius, the dendritic tip solute concentration and the dendrite tip undercooling composition and the degree of undercooling were obtained through theoretical analysis. The dendritic growth mode in cold melt was determined by EDS method.The concentration of liquid phase solute in the tip of dendrite during the solidification was approximately determined by EDS analysis, which is in good agreement with the prediction of BCT model, indicating that the BCT model can be successfully used to describe the Co_ (80) Pd_ ( 20) Dendrite growth in alloys.