Abstract: Solidification or crystal growth of metallic alloys is crucially determined by flow, heat and mass transfer, whilst the external imposed fields like electromagnetic field or gravitational environment can significantly influence these transfer processes. In this paper, two experiments are briefly presented to exhibit above influence on the microstructure evolution of metallic alloys, particularly on the Columnar-Equiaxed Transition (CET). Firstly, a sound rocket-based experiment demonstrates the effect of microgravity by comparison with that of ground-based experiment, and the quite different microstructure reveals that the natural convection plays an essential role in the solidification. Secondly, a quasi-two-dimensional solidifying experimental benchmark is presented to exhibit the natural and forced convection on the micro/macro segregation of the metallic alloys. The natural convection has been observed through the evolution of temperature field measured in real time, and this experiment exhibit the solute segregation naturally formed in the liquid and mushy zones. The forced convection driven by a traveling electromagnetic field interferes with solute segregation directly. Lastly, their influence mechanisms are analyzed and perspective of China's research strategy for material science in space is addressed.