Effect of composition on hydrogen absorbing properties in binary TiMn₂ based alloys

The hydrogen absorbing properties of binary TiMn₂ based alloys have been investigated as a function of composition in the range between Ti-56.4 and -66.8 at% Mn. The volume fraction of TiMn₂ phase increases with increasing Mn content. The Mn content of TiMn₂ phase is almost constant at compositions between Ti-56.4 and -59.4 at% Mn, while it increases with increasing Mn content at compositions between Ti-59.4 and -66.8 at% Mn. Ti-59.4 at% Mn containing TiMn₂ phase with 60 at% Mn exhibits the superior hydrogen absorption capacity and the least degradation of capacity during repeated hydrogen absorption and desorption. It is concluded that both hydrogen absorbing capacity and cyclic property in binary TiMn₂ based alloy are improved by increasing the volume fraction of TiMn₂ phase with keeping Mn content as low as possible.