Effect of Cr and Co additives on microstructure and electrochemical performance of Zr(NiVMn)2M0.1 alloys

Abstract Zr-based Laves alloys of Zr(NiVMn) 2 M 0.1 (M=Cr or Co) were prepared by an arc melting process. The effect of the Cr or Co additive on the microstructure and electrochemical performance of the Zr(NiVMn) 2 M 0.1 Laves phase hydride electrode alloys was investigated. Microstructure observation showed that the morphology of the Zr(NiVMn) 2 Cr 0.1 alloy was dendritic, while the morphology of the Zr(NiVMn) 2 Co 0.1 alloy was of equiaxial grains. The XRD results showed that both alloys consisted of the predominant C14 and C15 Laves phases, and the minor Zr 7 Ni 10 , Zr 9 Ni 11 non-Laves phases. There is no big difference in the amount of Laves phase in these two alloys as they were prepared under the same solidification conditions. The effect of the Cr or Co additive on phase composition and phase abundance of the obtained Zr(NiVMn) 2 M 0.1 alloys was quite similar. The electrochemical properties of the Zr(NiVMn) 2 M 0.1 alloys were dependent on the microstructures obtained. The electrode prepared from the alloy with equiaxial grain showed less activation cycles, higher discharge capacity and poorer cycle stability than those prepared from the alloy with dendrite structure. The microstructure-dependent electrochemical properties are also discussed.