CRYSTALLIZATION BEHAVIORS OF THE HYDROGENATED ZR-RICH AMORPHOUS ZRXNI1-X - H ALLOYS AND THE EFFECTS OF TITANIUM SUBSTITUTION

Abstract

In order to investigate the effect of hydrogen on the thermal stability of the amorphous ZrxNi1-x alloys, the crystallization of the hydrogenated alloys is examined using differential scanning calorimetry. By hydrogenation, the crystallization reaction is accelerated and the cubic ZrH2 phase is formed at first. At the next step, cubic ZrH2 is further transformed to the tetragonal structure. The corresponding mechanism is different from that of the as-received state and it is proposed to be related to the motion of nickel atoms, these having smaller atomic radius. When partially substituting titanium, the crystallization temperature and activation energy are greatly increased for both the as-received and the hydrogenated systems. This is thought to be caused by the retardation of the nickel diffusion and by hardening of the amorphous structure elastically, due to the presence of titanium atoms.