Microstructure and corrosion behavior of Zr–1.0Cr–0.4Fe–xMo alloys

Abstract

Possibility of using Mo as an alloying element in Zr-based alloys was attractive in terms of microstructure refinement and mechanical properties strengthening. In this research, Zr–1.0Cr–0.4Fe–xMo (0, 0.2, 0.4, and 0.6) alloys with different Mo contents were prepared by vacuum arc-melting method, the microstructure and the corrosion resistance of these alloys were investigated. Addition of Mo has a refinement effect on the microstructure; with the increase of Mo content, the α-laths in the as-cast samples and the grain size in the annealed samples decrease. Zr–1.0Cr–0.4Fe–xMo alloys have large numbers of fine second-phase particles (SPPs) in the matrix, the area fraction of the SPPs is more than 10 %. With the increase of Mo content, the population density of the SPPs increases significantly, while the average diameter of the SPPs decreases. Mo addition also affects the texture; the intensity of basal pole texture aligning normal direction decreases with the increase of Mo content in the alloys. Compared with Zr-4 and Zr–1Nb, Zr–1.0Cr–0.4Fe–xMo alloys have excellent corrosion resistance in 500 °C/10.3 MPa steam. The corrosion rates of Mo-containing alloys are higher than that of Mo-free alloy, which is mainly attributed to the solute Mo atoms in the Zr matrix. Change of the SPPs features due to the increase of Mo content alleviates the degradation of corrosion resistance in some degree, but it is not the dominant factor.