深过冷三元Fe35Cu35Si30合金的液相分离与枝晶生长特征

摘要

采用熔融玻璃净化技术研究了三元 Fe35Cu35Si30合金的液相分离与枝晶生长特征。实验获得的最大过冷度为328 K (0.24TL)。结果表明，合金在深过冷条件下具有三重凝固机制。当过冷度小于24 K时，α-Fe相为初生相，凝固组织为均匀分布的枝晶。过冷度超过24 K之后，合金熔体分离为富Fe区和富Cu区。在过冷度低于230 K的范围内，FeSi金属间化合物为富Fe区的初生相；当过冷度高于230 K时，Fe5Si3金属间化合物取代FeSi相成为富Fe区的初生相。随着合金过冷度的增加，FeSi相的生长速率逐渐升高，而Fe5Si3相的生长速率将逐渐降低。在富Cu区，初生相始终为FeSi金属间化合物。能谱分析表明，富Fe区和富Cu区的平均成分均已严重偏离初始合金成分。%Liquid Fe35Cu35Si30alloy has achievedthemaximum undercooling of 328 K (0.24TL) with glass fluxing method, and it displayed triple solidification mechanisms. A critical undercooling of 24 K was determined for metastable liquid phase separation. At lower undercoolings,α-Fe phase was the primary phase and the solidification microstructure appeared as homogeneous well-defined dendrites. When the undercooling exceeded 24 K, the sample segregated into Fe-rich and Cu-rich zones. In the Fe-rich zone, FeSi intermetallic compound was the primary phase within the undercooling regime below 230 K, while Fe5Si3intermetallic compound replaced FeSi phase as the primary phase at larger undercoolings. The growth velocity of FeSi phase increased whereas that ofFe5Si3 phase decreased with increasing undercooling. For the Cu-rich zone, FeSi intermetallic compound was always the primary phase. Energy-dispersive spectrometry analyses showed that the average compositions of separated zones have deviated substantially from the original alloycomposition.