Structure, phase composition after the mechanical activation of powder TiNi and its interaction with hydrogen

The interaction of hydrogen with multiphase system near the equiatomic composition of the Ti-Ni after high-energy mechanical activation in a planetary ball mill with an acceleration of 60g was studied. It is shown that mechanical activation leads to non-monotonic change in the average particle size due to destruction and subsequent agglomeration of particle. The widths of the X-ray lines of all phases begin to change after 10 seconds of mechanical activation. The lattice parameters of the TiNi (austenite) and TiNi₃ phases do not change after hydrogenation, while the lattice parameter of the Ti₂Ni phase increases by 2,5 %. Therefore, it can be assumed that the main interaction in the Ti - Ni system near the equiatomic composition occurs with the Ti₂Ni phase. Hydrogenation of a multiphase TiNi powder after 30 s of mechanical activation leads to a change in the Ti₂Ni lattice parameter, which corresponds to the Ti₂NiH_0,5 hydride parameter, and after 300 s, to Ti₂NiH_0,8. It is shown that there is a critical time for the accumulation of defects at high-energy mechanical activation and the destruction of oxide layers occurs with increasing hydrogenation time that facilitating the penetration of hydrogen into powders.

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