Surface wave phenomenon and microstructure evolution mechanism of electromagnetically levitated ternary Ti-Al-Fe alloy.

Electromagnetic levitation technique was performed to investigate the surface wave phenomenon and microstructure evolution mechanism of undercooled ternary Ti 50 Al 30 Fe 20 alloy. Under the condition of high undercooling, the formation process of surface waves on the levitated alloy surface were directly detected by high-speed camera. The cooling gas provided the external perturbation that promoted surface nucleation, providing the suitable site for surface wave generation. On the rotating semisolid alloy surface, the competition between centrifugal force and surface tension caused the surface wrinkling, leading to the formation of surface waves. The residual liquid phase was solidified in the vortex circulation flow, and the vortex-shape pattern was preserved during rapid solidification. With the increases of undercooling, the microstructure evolved from dendrites and interdendritic lamellar eutectics into uniform anomalous eutectics because of the independent nucleation and competitive growth of (βTi) and TiFe phase. The surface wave was formed only at high undercoolings, indicating this phenomenon was related to the fluidity in eutectic growth. In this case, the uniform microstructure was closer to satisfying the continuum medium hypothesis, and the homogeneous medium reduced the energy damage during wave propagation. In addition, the micromechanical properties were remarkably increased as undercooling rose owing to the microstructural morphology and solute trapping effect. • The formation process of surface waves were directly detected by high-speed camera. • Waves mainly attributed to surface nucleation, semisolid rotation and vortex flow. • Independent nucleation and competitive growth resulted in microstructure evolution. • The micromechanical properties were remarkably increased as undercooling rose. [ABSTRACT FROM AUTHOR]