Mechanical allowing 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 allowing 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 intermatallic phases are dependent on the chemical campositions of the starting powders.