Effect of heat treatment on microstructure and thermal stability of Ti19Hf4V40Mn35Cr2 hydrogen storage alloy

In order to improve the hydrogen storage capacity, Ti19Hf4V40Mn35Cr2 alloy was prepared with low-temperature heat treatment (973 K, 2 h/8 h/72 h, water quenching). Microstructure, hydrogen storage properties and hydrogen absorption/ desorption mechanism have been investigated. The results show that ascast and heat treated Ti19Hf4V40Mn35Cr2 alloys consist of BCC phase, C14 Laves phase and Hf-rich phase. Large amounts of equiaxed dendrite BCC phase and eutectic structure (BCC phase + C14 Laves phase) were formed after heat treatment. The hydrogen storage capacity at the room temperature comes the highest up to 2.34 wt% for holding 72 h, which is 12% points higher than the as-cast alloy. The activation energy of as cast Ti19Hf4V40Mn35Cr2 alloy was about 83.30 kJ/mol, and the activation energies of heat treated alloys decreased to 66.26 kJ/mol, which is caused by the decreasing stability of hydride after heat treatment. (c) 2022 Elsevier B.V. All rights reserved.

Automated summary

Ti19Hf4V40Mn35Cr2 alloy with improved hydrogen storage capacity was prepared through low-temperature heat treatment. The microstructure, hydrogen storage properties, and absorption/desorption mechanism were investigated. The results showed that heat treatment resulted in the formation of a large amount of equiaxed dendrite BCC phase and eutectic structure, leading to higher hydrogen storage capacity and lower activation energy.