Effect of 0.770wt%H addition on the microstructure of Ti–6Al–4V alloy and mechanism of δ hydride formation

Effect of temperature on hydrogen absorption characteristic and microstructural evolution of TC21 alloy

“…According to the previous analysis of the effect of temperature on hydrogen absorption characteristic in the present work, the most appropriate temperature is about 600 C. At this most appropriate temperature, titanium atoms have the maximal affinity with hydrogen atoms. When hydrogenation temperature is lower than 600 C, hydrides grow up slowly, so acicular and fragmentary hydrides precipitate in the specimen hydrogenated at 550 C. In addition, the solubility of hydrogen in the alloy decreases when temperature drops, so acicular hydrides precipitate at phase/grain boundaries owing to the hydrogen diffusion during cooling, which have been described in detail by Zhu et al [27] and Liu et al [28].…”

“…Fig. 8hej shows more morphologies of the microstructures in the specimen hydrogenated at 550 C. Generally, the grain/phase boundary is rich in defects and benefit to the nucleation [27,28], therefore it can be seen from Fig. 8hei that acicular d hydride precipitates at grain/phase boundary and grows up into the interior of grain/phase.…”

“…Hydrides are not found in the specimen hydrogenated at 750 C, it is because that b phase becomes the main phase owing to the decrease of a / b phase transformation temperature. The amount of stable elements for b phase (Mo, Cr and Nb) in TC21 alloy is larger comparing with that in TC4 alloy, and hydrogen concentration can exceed 2 wt.% without hydride formation in stable b-Ti alloys [29], moreover, the air-cooling rate is rapid, therefore the eutectoid transformation b H / a þ d cannot occur during air-cooling [27].…”

An Investigation of Phase Transformation in (Ti‐6Al‐4V)‐H Using in Situ High‐Energy Synchrotron XRD

“…In fact, since the early 1980s and well before the invention of HSPT, hydrogen was investigated for its ability to refine microstructure and improve mechanical properties for cast, wrought and PM Ti materials [7][8][9][10][11][12][13][14][15][16][17]. This method is referred to as thermohydrogen processing (THP).…”

Effect of hydrogen addition on the microstructure of TC21 alloy

“…Ultrafine grained titanium alloys were obtained through thermohydrogen treatment, and its refined microstructure benefits the superplasticity. Recently, Liu et al [17], Zhu and Li [18], Shan et al [19] and Luo et al [20] have studied the influence of hydrogen on the microstructural evolution and phase transformations of Ti-6Al-4V alloy and the mechanisms of ␦ hydride precipitation in both ␣ and ␤ phases. Since hydrogen has so many positive effects on titanium and titanium alloys, it is significant to study the influence of hydrogen on TC21 alloy as a candidate material for the structural parts of advanced aircraft.…”