Simulated evolution process of core-shell microstructures

Tao Qin, HaiPeng Wang, BingBo Wei
2007 Science in China Series G: Physics, Mechanics and Astronomy  
The evolution process of core-shell microstructures formed in monotectic alloys under the space environment condition was investigated by the numerical simulation method. In order to account for the effect of surface segregation on phase separation, Model H was modified by introducing a surface free energy term into the total free energy of alloy droplet. Three Fe-Cu alloys were taken as simulated examples, which usually exhibit metastable phase separation in undercooled and microgravity
more » ... It was revealed by the dynamic simulation process that the formation of core-shell microstructures depends mainly on surface segregation and Marangoni convection. The phase separation of Fe 65 Cu 35 alloy starts from a dispersed structure and gradually evolves into a triple-layer core-shell microstructure. Similarly, Fe 50 Cu 50 alloy experiences a structural evolution process of "bicontinuous phase → quadruple-layer core-shell → triple-layer core-shell", while the microstructures of Fe 35 Cu 65 alloy transfer from the dispersed structure into the final double-layer core-shell morphology. The Cu-rich phase always forms the outer layer because of surface segregation, whereas the internal microstructural evolution is controlled mainly by the Marangoni convection resulting from the temperature gradient. space environment, Fe-Cu alloy, phase separation, core-shell structure, numerical simulation Liquid phase separation of monotectic alloys has aroused great interest in the fields of materials physics and space science [1] [2] [3] . The earlier researches show that surface segregation and Marangoni convection resulting from the temperature gradient play an important role in the microstructural evolution under the space environment condition [2, 4] . Due to the opacity of metals and the form requirements of the experiments, it is quite difficult to carry out theoretical investigation deeply. Therefore, the evolution process and the micro-mechanism are still poorly understood. Numerical simulation has become an important method to explore phase separation. However, it has been exclusively implemented to study the pattern formation of polymers and little attention has been
doi:10.1007/s11433-007-0045-7 fatcat:yev36f6xabfsvczyzqn2uyuj7q