Effect of the microstructure on the corrosion resistance of ZIRLO alloy

The specimens of ZIRLO alloy were treated in different ways at 1000°C-0.5 h, 1000°C-0.5 h/560°C-10 h, 1000°C-0.5 h/C.R.(cold rolling)/560°C-10 h and 750°C-0.5 h, 750°C-0.5 h/560°C-10 h, 750°C-0.5 h/C.R/560°C-10 h respectively, and their microstructure was examined by transmission electron microscopy (TEM). At lastl, the corrosion characteristics were investigated with autoclave tests in 0.04M LiOH aqueous solution at 350°C, 16.8 MPa. It has been found that the corrosion resistance of specimens treated at 750°C-0.5 h/C.R/560°C-10 h is the best among all specimens treated in different ways in this work. It is concluded that a lower niobium concentration in solid solution in αZr matrix and a uniform distribution of nanoscale β Nb(containing iron) particles, especially the later one, are important factors for improving the corrosion resistance significantly. The cold deformation before the final annealing at 560°C plays an important role in obtaining nanoscale β Nb particles because it can promote the nucleation during the βZr decomposition.