As the lightest structural metal,Mg and Mg-based alloys have great potential applications in the aerospace,automotive and nuclear industries.However,such applications have been limited by low ductility and strength.Theoretically,small grain sized structure can synchronously improve its ductility and strength.Yet,universally reliable grain ref inement techniques for the magnesium alloys are still under investigation and some are in strong debating.This paper presents a brief review of development of grain ref inement methods for magnesium alloys,which would contribute to a better understanding of the factors controlling grain ref inement and provide an outlook of future research in this fi eld.
The microstructural evolution of the gas atomized Fe-25Cr-3.2C powders was investigated by using optical microscope, scanning electron microscope, and X-ray diffraction. The experimental results showed that the atomized Fe-25Cr-3.2C powders were mainly composed of austenite and （Fe,Cr）7 C3 carbide. Eutectic microstructure was developed in the larger particles, whereas dendritic microstrueture was obtained in the particles with diameter less than 38 μm. The reason for microstructure change should be the difference of nucleation undercooling for particles.
YANG Min SONG Chang-jiang DAI Yong-xiang ZHU Liang LI Ke-feng ZHAI Qi-jie
