Novel insight into evolution mechanism of second liquid-liquid phase separation in metastable immiscible Cu-Fe alloy

Publication date: 15 October 2018
Source:Materials & Design, Volume 156
Author(s): Shichao Liu, Jinchuan Jie, Bowen Dong, Zhongkai Guo, Tongmin Wang, Tingju Li
The metastable immiscible Cu80Fe20 alloys with different diameters were systematically investigated under conventional solidification. Experimental results indicated that the primary and second liquid-liquid phase separation simultaneously occur during solidification. The average size of primary phase-separated Fe-rich spherulites and the interior morphological pattern of minority Cu-rich phase can be greatly influenced by cooling rate due to the dynamic coupling between thermodynamic and kinetic effects. Moreover, various morphological patterns of minority Cu-rich phase in Fe-rich spherulites were observed, which discloses the dynamic evolution process during self-driven second liquid-liquid phase separation. The Marangoni migration, coalescence and coagulation, and Ostwald ripening are the dynamic mechanisms mainly responsible for various morphological patterns of minority Cu-rich phase after phase separation. Such a clear experimental observation of dynamic microstructure evolution for minority Cu-rich phase provides a strong and visualized evidence for the asynchronous crystallization behavior of primary phase-separated Fe-rich spherulites. Phase field simulation was also performed to reveal the dynamic evolution of minority Cu-rich phase during liquid-liquid phase separation. Besides, the experimental Cu80Fe20 alloys exhibit soft ferromagnetic characteristics possessing relatively low coercivity and high saturated magnetization. This present study provides a new strategy to design immiscible alloy with anticipated microstructure possessing tailored properties and desired functionalities.

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