EFFECT OF 0.037%H ON HIGH TEMPERATURE DEFORMATION BEHAVIOR OF A CAST Ti-45Al-5Nb-0.8Mo-0.3Y ALLOY

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 prop- erties 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 hydro- gen 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 microstruc- tures 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, ap- proximately 25% when deformed at 1200 and strain rate of 0.01 s 1 . The lamellar spacing of