Mechanical Alloying of the Ti–Ni System

There kinds of Ti–Ni elemental powders, Ti45Ni55, Ti50Ni50 and Ti55Ni45, were mechanically alloyed by a planetary ball mill for alloying times up to 10 h, and the alloying process and the microstructures after heating at temperature of 1273 K were investigated by powder X-ray diffractometry. The Ti55Ni45 powder formed an amorphous phase after mechanical alloying for 10 h, while the Ti50Ni50 powders formed a disordered b.c.c.-TiNi phase. The Ti45Ni55 powder also formed the disordered b.c.c.-TiNi phase at an intermediate stage of mechanical alloying but turned to an amorphous state with increasing alloying time. After heating at 1273 K, the Ti2Ni phase has been formed in all powders, and the ordered B2-TiNi (CsCl structure) phase was observed in the Ti50Ni50 and Ti45Ni55 powders, but a monoclinic TiNi phase in the Ti55Ni45 powder. In the Ti45Ni55 powder also the TiNi3 phase has been formed. The amounts of these intermetallic phases are dependent on the chemical compositions of the starting powders.