HYDROGEN IN HFTI2 ALLOY - A FORMATION OF THE HYDROGEN-STABILIZED HFTI2HX PHASE WITH THE C15-TYPE HOST LATTICE

X-ray diffraction study of the HfTi2Hx samples (0.5 less than or equal to x less than or equal to 5.95) obtained by hydrogenation of the dis ordered h.c.p. HfTi2 alloy has revealed the hydrogen-stabilized lambda phase with the ordered C15-type host lattice. The HfTi2Hx samples wit h x=4.0 and 4.5 are found to contain a single lambda phase. In the sam ples with 1.5 less than or equal to x less than or equal to 3.5 and 5. 0 less than or equal to x less than or equal to 5.95 the lambda phase coexists with the solid solution (alpha) and the dihydride (gamma, del ta) phases. The order parameter of the host-metal lattice in the lambd a phase is found to increase with increasing H content. (C) 1998 Elsev ier Science S.A.