Microstructure of Bi-containing zirconium alloys

The effect of Bi addition(0.05 wt%-0.50 wt%)on the microstructure of zirconium alloys,including T5(Zr-0.7 S n-1.0 Nb-0.3 Fe-0.1 Cr),S5(Zr-0.8 Sn-0.35 Nb-0.4 Fe-0.1 Cr),Zr-4(Zr-1.5 Sn-0.2 Fe-0.1 Cr) and Zr-1 Nb,was investigated by transmission electron microscopy(TEM),energy-dispersive spectroscopy(EDS) and selected area electron diffraction(SAED).Results show that with the increase in Bi content,h-Zr(Fe,Cr,Nb)2,o-Zr(Fe,Sn,Bi)_(2) and Zr-Fe-Cr-Nb-Sn-Bi second-phase particles(SPPs) precipitate successively in the T5+xBi and S5+xBi alloys;in the Zr-4+xBi alloys,h-Zr(Fe,Cr)2,o-Zr(Fe,Sn,Bi)2,Zr-Fe-Cr-Sn-Bi and Zr-Fe-Cr-Bi SPPs are detected successively.While as for Zr-1 Nb+xBi alloys,Bi-free SPPs appear.The addition of Bi promotes the precipitation of SPPs with Sn in the alloys.The concentration of Bi dissolved in α-Zr matrix increases with the decrease in Sn content in the alloys.Adding reasonable Bi has little influence on the solid solution content of Nb in α-Zr matrix.