Ni-32.5%Sn共晶合金的净化与深过冷

DENUCLEATION AND HIGH UNDERCOOLING OF Ni-32.5%Sn EUTECTIC ALLOY

本文采用循环高温过热和无机盐玻璃净化剂去除液态Ni-32.5%Sn共晶合金中的异质晶核,获得高达397K(0.283T_E)的过冷度,发现深过冷熔体主要以辐射方式散热,从而导出一种根据冷却曲线近似计算其平均比热的方法,采用高速摄影技术研究了其再辉过程,发现即使过冷度超过0.2T_E,液态合金仍然优先发生界面异质形核。

Large undercooling up to 397 K (0.283T_E) have been obtained for Ni-32.5%Sn eutectic alloy melt by superheating-cooling cycles and denucleating withinorganic glasses. The predominant dissipation of heat for highly undercooled alloymelt is through radiation. An approximate method was consequently derived to cal-culate its mean specific heat from measured cooling curves. With the aid of highspeed cinematography, it was revealed that the surface or interface heterogeneousnucleation takes place in preference to homogeneous nucleation even though theundercooling exceeded 0.2T_E.