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-p hase TiAl microstructures, respectively, were measured at temperatures up to 923 K in high pressure hydrogen, up to 10 MPa. The total hydrog en uptakes during: heating to 923 K at constant hydrogen pressures and during increasing the hydrogen pressure to 10 MPa at constant tempera tures increased with increasing amounts of the Ti3Al in the alloys. Th e Ti-25Al alloy cracked and then spontaneously disintegrated at high-h ydrogen pressures. A ternary (Ti-Al-H) hydride then formed, whose crys tal structure is the same as that of the gamma 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 th e Ti-45Al and Ti-53Al alloys during heating and during pressure increa se was released during cooling to room temperature or during pressure decrease to 0 MPa. (C) 1997 Elsevier Science S.A.