MECHANICAL ALLOYING OF THE TI-NI SYSTEM

There kinds of Ti-Ni elemental powders, Ti45Ni55, Ti50Ni50 and Ti55Ni4 5, were mechanically alloyed by a planetary ball mill for alloying tim es up to 10 h, and the alloying process and the microstructures after heating at temperature of 1273 K were investigated by powder X-ray dif fractometry. The Ti55Ni45 powder formed an amorphous phase after mecha nical alloying for 10 h, while the Ti50Ni50 powders formed a disordere d 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 tu rned to an amorphous state with increasing alloying time. After heatin g at 1273 K, the Ti2Ni phase has been formed in all powders, and the o rdered 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 TiNi; phase has been formed. The amou nts of these intermetallic phases are dependent on the chemical compos itions of the starting powders.