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 microstructures, 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 γ 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.