Effects of the Chromium Content in (TiVNb)100−xCrx Body-Centered Cubic High Entropy Alloys Designed for Hydrogen Storage Applications
Renato Belli Strozi, Daniel Rodrigo Leiva, Guilherme Zepon, Walter José Botta Filho, Jacques Huot
Abstract
In this paper, we report an investigation of adding a non-hydride forming element in the multicomponent Ti-V-Nb-M system. By the Calculation of Phase Diagrams approach (CALPHAD), the thermodynamic phase stability of the TiVNbT (T = Cr, Mn, Fe, Co, and Ni) was investigated, and Cr was selected as the fourth alloying element due its high tendency to stabilize body-centered cubic solid solutions (BCC). The (TiVNb)100−xCrx alloys (with x = 15, 25, and 35 at.% Cr) were synthesized by arc-melting. The structural characterization reveals that the three alloys were composed of a major BCC phase, which agrees with the thermodynamic calculations. The three alloys absorb hydrogen at room temperature without any activation treatment, achieving a hydrogen uptake of about H/M = 2. The Pressure-Composition-Isotherms curves (PCI) has shown that increasing the Cr amount increases the equilibrium pressures, indicating that tunable H storage properties can be achieved by controlling the alloys’ Cr content.