为了研究热氢处理技术对TiAl基金属间化合物Ti－45Al－5Nb－0.8Mo－0.3Y合金高温变形行为的影响规律,对未置氢和H含量为0.037% (质量分数)的铸态合金进行了等温热压缩实验,并利用SEM和TEM观察了合金压缩后的微观组织．结果表明,H可以降低合金的高温变形流动应力, 细化微观组织,提高合金的热加工性能．与未置氢合金相比, 在1200℃, 应变速率0.01 s^-1变形条件下,H可使合金的峰值流动应力下降25%左右．置氢处理促进了位错运动、动态再结晶和孪生变形, 并提高了β相的含量,这是置氢合金高温变形流动应力下降的主要原因．

TiAl－based alloys have been regarded as potential structural materials for the aerospace industry because of their high specific strength at elevated temperature, good creep properties and excellent resistance to oxidation. However, their low room temperature ductility and bad high temperature deformability are the considerable barriers to wide application of such alloys. It has been reported that thermo hydrogen treatment (THT) was an effective way to improve the formability of Ti－Al binary alloys. However, up to now few works have been done about the effect of THT on the mechanical properties of utilizable TiAl－based intermetallic compounds. So, the effect of hydrogen on high temperature deformation behaviors of a utilizable TiAl－based intermetallic compound, Ti－45Al－5Nb－0.8Mo－0.3Y alloy, was investigated. Isothermal hot compression tests of the cast Ti－45Al－5Nb－0.8Mo－0.3Y alloy containing 0 and 0.037%H (mass fraction) were carried out by use of a hot simulator at 1150 and 1200℃, with strain rates of 0.1 and 0.01 s^-1, and their microstructures were studied using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that hydrogen was able to decrease high temperature deformation flow stress and refine microstructure, which led to an improvement of the hot formability. Comparing with the unhydrogenated alloy, the hydrogenated alloy presented a reduction of peak flow stress, approximately 25% when deformed at 1200℃ and strain rate of 0.01 s^-1.The lamellar spacing of Hydrogenated Ti－45Al－5Nb－0.8Mo－0.3Y alloy was 265 nm, 77 nm less than that of the unhydrogenated alloy, which was mainly owing to hydrogen－increased β phase content. Besides, the increase of β phase with good high temperature plasticity was one of the main reasons for the decrease of flow stress of the hydrogenated alloy. Hydrogen made the peak strain of true stress and strain curves of the hydrogenated alloy occur earlier than that of the unhydrogenated alloy, which indicated that hydrogen promoted dynamic recrystallization of the hydrogenated alloy to decrease the flow stress. The dynamic recrystallization of β phase was found in the hydrogenated alloy, but not in the unhydrogenated alloy. Comparing with the unhydrogenated alloy, the density of dislocation of the hydrogenated alloy was lower because hydrogen induced the movement of dislocation. More twinning of γ phase occurred in the hydrogenated alloy, which assisted the alloy in high temperature deformation to some extent. In summary, hydrogen－induced dislocation movement, hydrogen－promoted dynamic recrystallization and twinning, and hydrogen－increased β phase content were the main reasons for the decrease of high temperature deformation flow stress of the hydrogenated Ti－45Al－5Nb－0.8Mo－0.3Y alloy.