Correlation between hydrogen distribution in V–4Cr–4Ti alloy and impact strength

Distribution of hydrogen isotopes was examined by tritium radioluminography using imaging plates for specimens of a V–4Cr–4Ti alloy prepared from two different plates fabricated with cold rolling under two different conditions (93% and 96% reduction in thickness) and recrystallization annealing. Influence of hydrogen on impact strength was also studied. Radioluminographs showed that tritium was concentrated in band-like regions where Ti(C,N,O) precipitates were densely distributed. The extent of tritium accumulation in the band-like regions and their shapes, however, were different between the two types of specimens; the band-like regions were thinner and more elongated, and the trapping effects of precipitates was smaller for the specimen prepared with higher extent of cold working. On the other hand, this type of specimen showed lower susceptibility to hydrogen embrittlement. These observations indicated that precipitate distribution prepared with higher extent of cold working is preferable to provide better durability against hydrogen embrittlement.