曹崇德
,
鲁晓宇
,
魏炳波
金属学报
采用熔融玻璃净化法使大体积Co85Cu15亚包晶合金的最大过冷度达到351K（0.21TL），实验测得其超过冷临界过冷度为379K.随着过冷度的增大，显微组织由树枝晶转变为等轴晶，并显著细化；溶质截留效应增强，显微偏析程度减小,Co的同素异构转变受到抑制，凝固组织中Co主要是亚稳的过饱和α-Co固溶体,ε-Co含量极少.对初生相形核率进行了理论计算，发现在过冷度为351K时合金熔体仍然发生异质形核.依据LKT／BCT枝晶生长理论对初生相生长速度和枝晶顶端半径进行了理论计算
关键词:
包晶合金
,
liquid metal
,
undercooling
,
rapid solidification
文强
,
坚增运
,
朱满
,
常芳娥
,
党博
金属学报
doi:10.3724/SP.J.1037.2013.00659
利用高速摄影仪和SEM研究了RE对Al-80％Si合金凝固过程中再辉界面形貌、初生Si形貌和凝固后组织的影响.结果发现,加入RE前后的Al-80％Si合金均存在2个临界过冷度△T1和△T2,在过冷度小于△T1时,初生Si的形貌为粗大的长片状,表面有明显的棱角;过冷度大于△T2后,合金在凝固过程中的再辉界面为平面状,凝固后的初生Si形貌为均匀、细小、表面有光滑凸起的球状,并且晶粒表面的棱角消失;当过冷度在△T1与△T2之间时,合金在凝固过程中的再辉界面为树枝状,凝固后的初生Si形貌部分为表面有棱角的片状和块状,部分为表面无棱角的球状.对于Al-80％Si合金而言,△T1和△T2分别约为132和250 K.RE能降低Al-80％Si合金△T1和△T2的值,对于Al-80％Si-1％RE而言,△T1和△T2分别约为60和199 K.
关键词:
Al-Si合金
,
初生Si
,
RE
,
过冷度
,
组织
C.X.Dong
,
X.Y.Luand B.B.Wei(Laboratory of Materials Sciencein Space
,
Northwestern Polytechnical University
,
Xi'an 710072
,
China)
金属学报(英文版)
The Ag-Ge eutectic alloy system was intensively investigated with respect to its solidification characteristics at large undercoolings which were obtained by the B2O3 glass fluxing technique combined with argon protection. Grain size refinement was found in the Ag-15 wt% Ge hypoeuteciic alloy. With inereasing undercoolings the feather-like structure disappeared in the Ag-19wt% Ge eutectic alloy, and even silver slips showed up at sufficient undercoolings. Nevertheless, the fact that germanium had nucleated in preference to silver was indicated by a fine germanium line in the middle of the silver slips. The various morphologies of the germanium phase in the Ag-25 wt% Gehypereutectic alloy including the five-fold symmetry structure were explained by the joint action of high undercoolings (i.e. growth velocities) and density differences. The corpled zone of this alloy system was qualitatively estimated.
关键词:
Ag-Ge alloys
,
null
,
null
,
null
李强
,
金明江
,
应仁龙
,
金学军
金属功能材料
通过DSC热分析技术研究了成分和升降温速率对GaInSn三元合金和GaIn二元合金的固-液相变行为的影响.结果表明,GaInSn三元合金和GaIn二元合金升温过程中的固-液转变(熔化)温度十分稳定,对成分波动不敏感;而降温过程中的液-固转变(凝固)温度则随成分的波动而显著变化.此外,讨论了Ga基合金过冷度与Ga含量和冷却速率之间的关系.
关键词:
镓基合金
,
过冷度
,
相变
J.F. Li
,
J.G. Li
,
X.P. Zhang and Y.H. Zhou (School of Materials Science and Engineering
,
Shanghai Jiao Tong University
,
Shanghai 200030
,
China)
金属学报(英文版)
Bulk Fe-30Ni alloy melt was nudercooled up to 337K by combining the glass fluxing technique with superheating-cooling cycle. Grain refinement at low undercoolings was observed in the experiment in addition to that at high undercoolings. The current grain refinement mechanisms were examined, and it is concluded that the refined gains are all developed from dendrites, however the grain refinement at low undercoolings is due to chemical superheating, while that at high undercoolings due to rapid solidification contruction.
关键词:
Fe-Ni alloy
,
null
,
null
