Hydrogen uptake in titanium aluminides in high pressure hydrogen

The weight gains of Ti-25Al, Ti-45Al and Ti-53Al alloys, with typical single-phase Ti₃Al, two-phase Ti₃Al/TiAl (fully lamellar) and single-phase TiAl microstractures, respectively, were measured at temperatures up to 923 K in high pressure hydrogen, up to 10 MPa. The total hydrogen uptakes during heating to 923 K at constant hydrogen pressures and during increasing the hydrogen pressure to 10 MPa at constant temperatures increased with increasing amounts of the Ti₃Al in the alloys. The Ti-25Al alloy cracked and then spontaneously disintegrated at high-hydrogen pressures. A ternary (Ti-Al-H) hydride then formed, whose crystal structure is the same as that of the y hydride (f.c.c.), known in the titanium-hydrogen binary system. No hydride could be detected in the Ti-45Al and Ti-53Al alloys. Most of the hydrogen taken up in the Ti-45Al and Ti-53Al alloys during heating and during pressure increase was released during cooling to room temperature or during pressure decrease to 0 MPa.