Orientation relationship and interfacial structure between alpha-Nb5Si3 and Nb solid solution in the eutectic lamellar structure

摘要

The orientation relationship (OR) and the interfacial structure of the eutectic alpha-Nb5Si3 and Nb solid solution (Nbss) lamellar microstructure were investigated by transmission electron microscopy (TEM). The OR between alpha-Nb5Si3 and Nbss was determined as (002)(alpha)//(002)(Nb) and 310(alpha)//110(Nb). In spite of the significant difference in crystal structure between alpha-Nb5Si3 and Nbss, the interface was found to be semi-coherent with good matching. High-resolution TEM images of the alpha-Nb5Si3/Nbss interface are presented to describe the chemistry of the terminating plane of alpha-Nb5Si3. The results revealed that a pure Nb layer not Si or mixed (Nb + Si) layer of the alpha-Nb5Si3 phase was bonded to the Nb phase at the interface. A periodic array of edge-type misfit dislocations, with line direction 1 (1) over bar0(Nb) and Burgers vector 1/21 (1) over bar0(Nb), was observed at the interface.