深过冷Ni-Sn合金非规则共晶的形成机制  

The formation mechanism of anomalous eutectic in highly undercooled Ni-Sn eutectic alloy

作　　者：陈达[1] 杨根仓[1] 刘峰[1] 周尧和[1] 

机构地区：[1]西北工业大学凝固技术国家重点实验室

出　　处：《材料研究学报》2007年第2期209-214,共6页Chinese Journal of Materials Research

基　　金：国家自然科学基金(50395103;50271057;50501020);西北工业大学校英才培养计划资助项目

摘　　要：采用熔融玻璃净化配合循环过热使Ni-32．5％Sn(质量分数)共晶合金实现了深过冷快速凝固．当过冷度大于某一临界值时,非规则共晶在凝固组织中出现．随着过冷度的提高,最终得到完全的非规则共晶组织．通过分析Ni-Sn共晶合金中各相形核、生长、以及枝晶熔断机制随过冷度的变化,解释了非规则共晶的形成机制．在深过冷条件下熔体中初生相率先形核并长入过冷熔体中,形成枝晶骨架,再辉重熔后次生相从残余熔体中析出并包围初生相,形成非规则共晶．A＇pplying glass flux combined with cyclical superheating, high undercooling were achieved in Ni-32.5%Sn eutectic alloy melt. The anomalous eutectic was observed in the as-solidified microstructure. The volume fraction of the anomalous eutectic increases with undercooling, and when undercooling was exceeding a critical value, the as-solidified microstructure was totally occupied by anomalous eutectic. In terms of competitive nucleation and growth between α（Ni） and Ni3Sn, and remelting of α（Ni） dendrites, the forming mechanism of anomalous eutectic was interpreted. Subjected to high undercooling, rapid primary solidification leads to the growth of primary dendrites, thus resulting in rapid recalescence and subsequent remelting of the primary dendrites. Then secondary phase is solidified from the remained liquid, and surrounds the primary dendrites fragments, so the anomalous eutectic is formed.

关 键 词：金属材料 深过冷 Ni—Sn共晶 非规则共晶 

分 类 号：TG244[金属学及工艺—铸造]