Formation and evolution process of needle hydride of BT16 alloy after hydrogenation

To understand deeply the influence of hydrogenation on the BT16 alloy microstructure and obtain a microstructure with good properties of cold heading, optical microscopy (OM), and X-ray diffractometry (XRD) are used to analyze the microstructure and phase composition of BT16 alloy after hydrogenation. The results show that the BT16 alloy phase transforms froms α+β to β at 780°C in the process of hydrogenation, and Widmanstatten structure is generated after cooling. The α phase can be found in all samples with different hydrogenation time, and its content decreases as the hydrogenation time increases; hydrides appear in the process of hydrogenation. This suggests that because of hydrogenation, the transition temperature at which the BT16 alloy phase transforms from α+β to β drops below 800°C, and the hydrogen content influences the existing form of hydrides. As the hydrogen content increases, the TiH phase appears earlier, the TiH_1.5 phase and TiH₂ phase appear later, all of which are needle hydrides.