Fe-Cu合金相分离过程

Liquid Phase Separation of Fe-Cu Alloy

采用喷铸和单辊旋淬快速冷却法制备Fe_(80)Cu_(20),Fe_(60)Cu_(40),Fe_(50)Cu_(50)3种成分Fe-Cu合金,利用SEM,XRD,DSC对其凝固微观组织、相结构及相变热力学过程进行观察和分析。结果表明:3种成分的Fe-Cu合金均发生了不同程度的相分离,且Cu含量越高,DSC降温曲线上出现的液-液相分离温度越高,结晶组织中相分离现象越明显;Fe_(80)Cu_(20)合金随着过冷度的增加,富Fe相枝晶晶粒尺寸变小的同时富Cu相的体积分数也不断减少,而Fe相、Cu相的晶格常数均随过冷度的增加而增大,过冷度的增加提高了分离相的固溶度;在Fe_(60)Cu_(40)及Fe_(50)Cu_(50)合金中富Cu区出现二次相分离的富Fe小球,且富Fe小液滴不断聚集以降低界面能。揭示了Fe-Cu相分离型合金的快速凝固过程。

Three kinds of Fe-Cu alloys Fe80 Cu20, Fe60 Cu40, Fe50 Cu20 were prepared respectively by spray casting and melt-spinning way. The microstructure, thermodynamics properties of Fe-Cu alloys during phase separation process were observed and analyzed through SEM, XRD and DSC measurement. The results show that three different Fe-Cu alloys have different levels of phase separation, the initial temperature of liquid-liquid （L-L） phase separation increases with increasing Cu content, meanwhile, phase separation phenomenon is more obvious. The grain size of Fe-rieh phase and the volume fraction in Fe80Cu20 decreases with increasing degree of undercooling, while the crystal lattice constant of both Fe and Cu phases increases gradually. The increasing degree of undercooling improves the solid solubility of phase separation. The Fe-rich balls formed due to secondary L-L phase separation in Cu-rich phase are also observed in Fe50Cu50 and Fe60Cu40 alloys. The growth of the Fe-rieh balls is the coagulation process of the two adjacent balls by the migration of smaller balls moving towards the bigger ones to reduce of interfacial energy. The rapid solidification process of Fe-Cu alloy with miscibility gap has been revealed .