Effect of trace Ce and B additions on the microstructure of Nb-3Si-22Ti alloys

The effects of trace Ce and B additions on the microstructure Nb-22Ti-3Si alloys were studied.The microstructure of the alloys was observed by scanning electron microscope（SEM）,and their phase compositions were analyzed with X-ray diffraction（XRD） and Electro-Probe micro-analyzer（EPMA）.The distributions of the elements were detected by Spectrum analyzer.The interface of the phases in the alloys was investigated by transmission electron microscopy（TEM）.The results indicated that two phases of Nbss and Nb3Si presented in Nb-22Ti-3Si,Nb-22Ti-3Si-0.2Ce and Nb-22Ti-3Si-0.2B alloys.The segregation of Ti at the interface between Nbss and Nb3Si was promoted and the volume fraction of silicides in the alloy increased with the trace B and Ce addition to the Nb-22Ti-3Si alloy respectively.And there was no single and definite orientation relationship between Nb3Si and Nbss in Nb-22Ti-3Si,Nb-22Ti-3Si-0.2Ce and Nb-22Ti-3Si-0.2B alloys.Compared with the Nb-22Ti-3Si alloy,the Nbss superlattice structure was found in Nb-22Ti-3Si-0.2Ce and Nb-22Ti-3Si-0.2B alloys.