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

We have investigated the hydrogen absorbing properties of binary TiMn ₂ based alloys with the compositions ranging from Ti-56.4 to 66.8 at% Mn, which were prepared by rapid solidification and subsequent annealing. All the alloys are composed of the TiMn₂ and TiMn phases, where the volume fraction of the TiMn₂ Laves phase increases with increasing Mn content. In the annealed alloys with Ti-56.4 to -59.4 at% Mn, the Mn content of the TiMn₂ phase is about 60 at.%; whereas in the alloys with 59.4 to 66.8 at.%, it increases with increasing the Mn content of the alloys. Correspondingly, the hydrogen absorbing capacity of the alloys increases with increasing the Mn content up to 59.4 at.%, but rapidly decreases with a further increase of the Mn content These observations suggested that the alloy composition exhibiting the maximum hydrogen absorbing capacity is determined by a compromise of a high volume fraction and a low Mn content of the TiMn ₂ phase.-In addition, we found that rapidly solidified alloys exhibited poor hydrogenation behavior. Therefore, it is concluded that the hydrogen absorbing capacity of the binary TiMn₂ based alloys is mainly governed by the composition of alloy and possibility by the atomic arrangement of excess Ti atoms within the TiMn₂ phase.