Abstract
Abstract Based on as-cast high-entropy CrFeMnTiVZr alloy, this study changes the amount of Cr and Mn contents in the formula, and thus derives several equal- and non-equal-molar six-component (both x and y ≠ 0), and two equal-molar five-component (one of x and y = 0) CrxFeMnyTiVZr (Crx and Mny) alloys. It aims to investigate how Cr and Mn contents influence the hydrogen absorption and desorption behaviors of the as-cast high-entropy CrFeMnTiVZr alloy. In experiments, vacuum arc remelter made the as-cast samples; XRD and SEM analyzed their microstructure; EDS identified chemical compositions of the concerned phases and the alloys; hydrogen absorption kinetic curves identified hydrogen absorption mechanisms; and PCI curves elucidated hydrogen absorption and desorption behaviors; as well as DSC measured hydrogen desorption temperatures of alloy hydrides. CrxFeMnyTiVZr alloys are of a “pseudo-AB2” (A = Ti, Zr; B = Cr, Fe, Mn, V) C14 Laves phase structure. SEM BEI showed that their structure possesses dendrite, interdendrite, and little amount of V-rich precipitate in the interdendrite. Their XRD peaks shift to large angles, as x and y increase. Multi-component mixing effect and off-stoichiometry in AB2 of the alloys generate anti-site substitution between ‘A’ and ‘B’ atoms, make the C14 lattice distorted, and thus cause the peak broadening in their XRD patterns. The 90%-to-the-saturation time for the alloys, t90, shown in hydrogen absorption kinetic curves, is within 60 s. The long, steep PCI curves are due to the “disordering” effect caused by the multi-component mixing in the alloys. The value of the maximum hydrogen absorption of the alloys, (H/alloy)max, reaches 2 wt% in this experiment. As the Cr and Mn contents increase, their hydrogen absorption decreases, mainly influenced by the related formation enthalpy of the alloys, and their hydrogen absorption pressure increases principally affected by the size of Cr and Mn atoms. Keywords: CrxFeMnyTiVZr hydrogen storage alloys, anti-site substitution, C14 Laves phase, pseudo-AB2