过冷Co_(75)B_(25)合金的凝固  

Solidification of Undercooled Co_(75)B_(25) Alloy

作　　者：李芸 刘连杰 李新明 李金富[1,2] LI Yun;LIU Lianjie;LI Xinming;LI Jinfu(State Key Laboratory of Metal Matrix Composites,School of Materials Science and Engineering,Shanghai Jiao Tong University,Shanghai 200240,China;Shanghai Key Laboratory of Materials Laser Processing and Modification,School of Materials Science and Engineering,Shanghai Jiao Tong University,Shanghai 200240,China)

机构地区：[1]上海交通大学材料科学与工程学院金属基复合材料国家重点实验室,上海200240 [2]上海交通大学材料科学与工程学院上海市激光制造与材料改性重点实验室,上海200240

出　　处：《金属学报》2018年第8期1165-1170,共6页Acta Metallurgica Sinica

基　　金：国家自然科学基金项目Nos.51471108和51620105012~~

摘　　要：利用熔融玻璃包覆加循环过热技术将Co75B25包晶合金熔体过冷至液相线下不同温度,通过凝固组织观察结合冷却曲线分析,确立了其凝固路径。结果表明:所有过冷度凝固后的试样中均只有a-Co和Co2B相,Co2B相与残余液相反应形成Co3B相的包晶转变被完全抑制,且在344 K实验所得最大过冷度下Co3B相也不能作为初生相析出;即使降低冷速至5 K/min,合金在小过冷度下凝固时也没有发生包晶反应。The method to deeply undercool alloy melts far below the liquidus temperature by eliminating heterogeneous nucleation sites inside is frequently used in studying non-equilibrium solidification behavior, preparing quasi-crystal, amorphous alloy and other metastable materials. Previous work on the solidification of Co-（18.5~20.7）%B（atomic fraction） alloys indicated that metastable Co23 B6 phase instead of stable Co3 B phase was formed as the primary phase from the melts undercooled by larger than 60 K.To know whether Co23 B6 phase can still primarily form from the deeply undercooled melt of Co75 B25, the nominal composition of Co3 B phase, the Co75 B25 alloy melt was undercooled to different degrees using the glass fluxing technique, and the solidification path was identified by analyzing the microstructures and cooling curves of the samples. There was nothing other than a-Co and Co2 B phases to form during solidification, indicating that not only the peritectic reaction of L（liquid） and Co2 B into Co3 B, predicted by the Co-B phase diagram, but also the formation of Co3 B as primary phase at large undercooling were inhibited. The peritectic reaction did not occur even though the solidification was designed to occur at a very small undercooling and a cooling rate decreased to 5 K/min.

关 键 词：Co75B25合金 过冷 非平衡凝固 相选择 

分 类 号：TG111.4[金属学及工艺—物理冶金]