Mechanical alloying and subsequent annealing effects on evolution of microstructure and morphology of TiH2-Ni powders

Mechanical alloying and subsequent annealing treatment were carried out to investigate the evolution of the microstructure and morphology of the TiH2-Ni system. The Ni(Ti) solid solution was formed in the initial milling process. When the milling time was 60 h, the alloy with uniform elemental distribution showed an amorphous structure containing a small amount of TiH2 nanocrystalline phase. The annealing treatment at 693 K contributed to a completion of amorphization for the alloy milled for 60 h. For the treatment at 1 073 K, a crystallization reaction for the amorphous phase occurred, leading to the formation of Ti2Ni, TiNi, and TiNi3 compounds by a short time treatment. Moreover, a separation of Ni-rich phases from the matrix and a phase transition among these three compounds occur by a long time treatment.