深过冷凝固Co₈₀Pd₂₀合金中的枝晶生长

来源期刊：金属学报2011年第4期

论文作者：周圣银 胡锐 蒋力 李金山 寇宏超 常辉 周廉

文章页码：391 - 396

关键词：深过冷； 快速凝固； 枝晶生长； 溶质截留； Co₈₀Pd₂₀合金

Key words：undercooled； rapid solidification； dendrite growth； solute trapping； Co₈₀Pd₂₀ alloy

摘    要：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Co₈₀Pd₂₀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Co₈₀Pd₂₀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Co₈₀Pd₂₀合金中的枝晶生长.

Abstract: Much interest has been focused on the dendrite growth of undercooled melts in the theoretical field of solidification research.The BCT model was widely accepted to interpret dendrite growth behavior in rapid solidification process.In present case,substantial undercoolingΔT up to 415 K was achieved for Co₈₀Pd₂₀ melt applying molten glass denucleation combined with cyclic superheating. The dendritic morphology of the experimental alloy was investigated by OM and the solute concentration of appointed micro-area was analyzed by EDS.Based on the BCT dendrite growth model,the theoretical calculation of the related parameters of the dendrite growth process included tip radius R,dendrite growth velocity V,solute concentration in liquid at dendrite tip C_L^* and undercooling contributions were completed.It can be found that the dendritic morphology was only formed in the undercooling ranges of 0-72 K and 95-142 K.With the initial undercooling increasing,V rises steeply due to the increase of the growth driving force,but R displays a complicated variation attributed to the combine effects of thermal/solute diffusion.EDS analysis reveals that the experimental data of C_L^* is in accordance with the theoretical predication by BCT model.The results confirmed that the dendrite growth in undercooled Co₈₀Pd₂₀ melts can be interpreted successfully by BCT model.