Intra-microstructures of FeNi Metal in Eutectic Blobs

Abstract

Our SEM and TEM studies revealed that the dendrites in FeNi–FeS eutectic nodules/blobs in both shock-produced melt veins and melt pockets of the Yanzhuang meteorite show zoning in their microstructures, which indicates non-equilibrium solidification of metal phase. In melt veins, three asymmetric microstructural and compositional zones: core, Ni-rich rim and martensite between the core and ring were discovered, while in melt pockets, a typical symmetric core-crust microstructure consisting of martensitic interiors and Ni-rich rim was revealed. It is suggested that the difference in cooling rates following shock-induced high-temperature melting might be an important factor in producing different dendritic microstructures in melt veins and melt pockets. The solidification environment might be considered as the second influence factor.