Speaker
Description
High-entropy alloys based on Ti, V, Nb, Cr and Mn have attracted interest as potential hydrogen storage materials due to the possibility of tailoring their structural and hydrogen sorption properties through compositional and processing modifications. In this study, the phase composition, microstructure and hydrogen absorption behaviour of TiVNbCrMn and TiVNbCrMnFe alloys prepared by arc melting were investigated using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and transmission electron microscopy (TEM) combined with selected-area electron diffraction (SAED).
The TiVNbCrMn alloy exhibited a predominantly body-centred cubic (bcc) structure with the Im-3m space group, confirmed by XRD and TEM/SAED. Its microstructure showed a pronounced dendritic morphology with a relatively homogeneous elemental distribution. In contrast, TiVNbCrMnFe exhibited a multiphase structure dominated by a hexagonal phase (P6₃/mmc) accompanied by a minor bcc phase (Im-3m). TEM/SAED confirmed the coexistence of these phases, with the dendritic regions associated mainly with the hexagonal phase and the interdendritic regions with the bcc phase and Ti-V enrichment.
Hydrogen absorption measurements at 35 °C revealed substantially different behaviour. TiVNbCrMn showed rapid initial hydrogen uptake, reaching approximately 1.9 wt.% within 100 min, followed by slower absorption and a final hydrogen content of approximately 2.55-2.6 wt.%. TiVNbCrMnFe exhibited lower hydrogen uptake, reaching approximately 0.9 wt.% within the investigated pressure range, without a distinct plateau region.
The results demonstrate a strong relationship between phase composition, microstructure and hydrogen absorption behaviour. The predominantly bcc TiVNbCrMn alloy exhibited substantially higher hydrogen uptake than the multiphase TiVNbCrMnFe alloy. The obtained results provide a basis for further investigation of thermal treatment as a means of modifying the structural state and hydrogen storage properties of high-entropy alloys.
Acknowledgment.
This work has been supported by the grants EU NextGenerationEU through the Recovery and Resilience Plan for Slovakia under the project No. 09I03-03-V04-00264.
