Computer Simulation Of Liquid Phase Separation Of Rapidly Solidified Cu-Fe Based Alloys By Phase Field Method

Because of the high-electric, high-thermal conductivity and high strength, the Cu-Febased alloys were widely used as structure-functional materials in aviation, automotivefield, communication technologies as well as electronics manufacturing industry. It isobvious that the liquid phase separation took place when these alloys were rapidlysolidified. The liquid phase separation in Cu-Fe based system were studied via computersimulation based on the continuous phase field method. The effects of concentration,temperature and the gradient energy coefficient on the separation process in Cu-Fe binaryalloy were analyzed. Meanwhile, the characters of liquid phase separation in Cu-Fe basedsystem with the addition of different alloying elements were discussed. Especially, theinfluence mechanism of alloying elements were illustrated. At last, using laser rapidsolidification, the microstructures of liquid phase separation were obtained and comparedwith the simulated results.The simulation of liquid phase separation in Cu-Fe binary system revealed that themelt separated into the Cu-rich phase and Fe-rich phase when it was undercooled into themiscibility gap. If the concentration of Fe is equal to that of Cu, the microstructure isinterconnected. Otherwise, the morphology with the spherical second-phase particlesembedded in a major liquid-phase matrix was observed. With the decrease of temperature,the speed of separation process increased and the microstructure did not changesignificantly. The increase of gradient energy coefficient resulted in thicker interface andcoarser particles. The liquid phase separation slowed down at the same time.The simulation of liquid phase separation in Cu-Fe-X(X:Cr, Ni) system indicated thatthe melt separated into Cu-rich phase and (Fe, X)-rich phase. The addition of Cr facilitatedthe separation process. The distribution characters of Ni and Cr in Cu-Fe based system were different. That was Cr had little solubility in Cu-rich phase, but had a certainsolubility in (Fe, Cr)-rich phase. In contrast, the concentration difference of Ni in twophases was relatively small. The (Fe, Cr)-rich particles were spherical while the (Fe,Ni)-rich particles were irregular. One of the reasons was the addition of Cr increase thecritical temperature of miscibility gap in Cu-Fe based system, which led to the sufficienttime for (Fe, Cr)-rich particles to grow and coarse. Another reason was the interfacialenergy between particles and matrix is larger in Cu-Fe-Cr system. The microstructuresdetermined by experiments were similar to the simulated results and proved the validity ofthem.