Spatial distribution of HfBi in metallurgically and electrochemically formed Bi-Hf alloy

Abstract

This study presents the spatial distribution of HfBi intermetallic compound in Bi-Hf alloy formed by potentiostatic electrodeposition to investigate the feasibility of density-based separation between Zr and Hf in liquid Bi phase. Prior to electrochemical alloy formation, four Bi-Hf alloys were produced metallurgically with the consideration of the Hf concentration in the alloy and the mixing effect on the liquid Bi. Then electrochemical behaviors of HfCl4 in LiCl-KCl were investigated by cyclic voltammetry (CV) using tungsten and Bi coated electrode at 500 °C. The apparent reduction potential and diffusion coefficient were calculated by determination of reversibility for single redox reaction of Hf4+/Hf. Two Bi-Hf alloys were produced by potentiostatic electrodeposition in LiCl-KCl-HfCl4/Bi system at 500 °C. Applied cathodic potential of −1.1 V vs. Ag/AgCl 1 wt % was determined from the CV results. The spatial distribution of intermetallic compound was obtained on the vertical cross section of Bi-Hf alloys. HfBi phase was characterized by SEM-EDS and XRD analysis. It is identified that HfBi was clearly formed and precipitated in the bottom of the Bi-Hf alloy during the electrodeposition, supporting the possibility of the separation of Hf from Zr by their density differences.