Improvement of cyclic durability of BCC structured Ti-Cr-V alloys

Durabilities of Ti-Cr-V alloys were investigated using the cyclic hydrogen absorption-desorption test. The XRD pattern obtained for Ti24Cr36V40 alloy after 100 cycles suggested the production of a highly distorted secondary phase. A temperature swing cyclic test was conducted and it became clear that the degradation of hydrogen transfer was caused by the decrease of total hydrogen content in the alloy. Vanadium content is an important factor in improving durability. High vanadium content prevents rapid degradation in the initial cycles. Floating zone melting is effective also for improving durability and the effect is remarkable for alloys with high vanadium content. Highly homogenized Ti8Cr12V80 alloy made by floating zone melting shows only 1.4% degradation from the initial hydrogen capacity after 500 cycles. As a behavior different from other Ti-Cr-V alloys, the floating zone melted Ti8Cr12V80 alloy shows an increase of the hydrogen absorption plateau pressure with the progression of cycles.