深过冷Cu-20%Pb亚偏晶合金的再辉与形核分析

Analysis on recalescence and nucleation of undercooled Cu-20%Pb hypomonotectic alloy

采用熔融玻璃净化与循环过热相结合的方法研究Cu-20％Pb亚偏晶合金的再辉行为，利用经典形核理论与瞬态形核理论计算讨论偏晶合金的两相竞争形核规律。结果表明，在过冷度0～238K范围内，凝固过程出现两次再辉。一次再辉由α（Cu）相的形核和生长引起，二次再辉由偏晶反应引起。过冷亚偏晶Cu-20％Pb合金凝固过程中，α（Cu）相恒先形核，即匀晶转变先于偏晶反应发生。

The recalescence behavior of Cu-20% Pb hypomonotectic alloy was investigated by means of combination of melted glass denucleation and cyclical superheating. Phase competitive nucleation in the alloy was discussed by classical nucleation theory and transient nucleation theory. It can be concluded that there are twice recalescence in solidification process of Cu-20% Pb hypomonotectic alloy with undercooling in the range of OK to 238K. The first recalescence is caused by nucleation and growth of a（Cu） dendrites and the second one is attributed to monotectic reaction. That is to say, the isomorphous transformation occurs earlier than the monotectic reaction no matter how large the undercooling is.