Composition design, synthesis and hydrogen storage ability of multi-principal-component alloy TiVZrNbTa.

• Thermodynamic model of single-phase high entropy alloys formation was developed. • Single-phase TiVZrNbTa equiatomic alloy was synthesized by various techniques. • Effect of synthesis method on alloy hydrogenation behavior was examined. • Alloy synthesis from melt results in improved stability upon hydrogenation. A thermodynamic model was proposed to assess the feasibility of the synthesis of single-phase multi-principal-component alloy. Based on this model, single-phase TiVZrNbTa equiatomic alloys with body centered cubic (BCC) structure were obtained by arc melting (AM), electron beam melting with pendant drop melt extraction (EBM-PDME) and mechanical alloying (MA). The alloys were characterized by powder X-ray diffraction, scanning and transmission electron microscopy, thermal analysis and mechanical testing. The hydrogenation behavior of the synthesized materials was studied by a volumetric method. It was found that for AM and EBM-PDME alloys a complete BCC-to-FCC structure transformation occurs upon hydrogenation, and hydrogen concentration in the hydrides formed reaches 1.5 H/M (1.6 wt%). MA alloy undergoes partial amorphization with maximum hydrogen absorption capacity of 0.9 wt%. [ABSTRACT FROM AUTHOR]