Phase Selection in Solidi?cation of Undercooled Co–B Alloys  

作　　者：X.X.Wei W.Xu J.L.Kang M.Ferry J.F.Li 

机构地区：[1]State Key Laboratory of Metal Matrix Composites,School of Materials Science and Engineering,Shanghai Jiao Tong University,Shanghai 200240.China [2]Australian Research Council Centre of Excellence for Design in Light Metals,School of Materials Science and Engineering,The University of New South Wales,Sydney,NSW 2052,Australia

出　　处：《Journal of Materials Science & Technology》2017年第4期352-358,共7页材料科学技术（英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.51227001 and 51471108);the SJTU-UNSW Cooperative Research Fund(16X120030005)

摘　　要：A series Co-（18.5–20.7） at.% B melts encompassing the eutectic composition（Co81.5B18.5） were solidified at different degrees of undercooling. It is found that the metastable Co23B6 phase solidifies as a substitute for the stable Co3 B phase in the alloy melts undercooled above a critical undercooling value of -60 K.The Co23B6 and α-Co phases make up a metastable eutectic. The corresponding eutectic composition and temperature are Co80.4B19.6 and 1343 K, respectively. On exposure of the metastable Co23B6 phase at a given temperature above 1208 K, it does not decompose even after several hours. But it transforms by a eutectoid reaction to α-Co ＋ Co3 B at lower temperature.A series Co-（18.5–20.7） at.% B melts encompassing the eutectic composition（Co81.5B18.5） were solidified at different degrees of undercooling. It is found that the metastable Co23B6 phase solidifies as a substitute for the stable Co3 B phase in the alloy melts undercooled above a critical undercooling value of -60 K.The Co23B6 and α-Co phases make up a metastable eutectic. The corresponding eutectic composition and temperature are Co80.4B19.6 and 1343 K, respectively. On exposure of the metastable Co23B6 phase at a given temperature above 1208 K, it does not decompose even after several hours. But it transforms by a eutectoid reaction to α-Co ＋ Co3 B at lower temperature.

关 键 词：UNDERCOOLING Rapid solidi?cation Metastable phase diagram Structure evolution 

分 类 号：TG113.12[金属学及工艺—物理冶金]