Solid state synthesis of nanocrystalline and/or amorphous 50Ni–50Ti alloy

A nanocrystalline/amorphous 50Ni–50Ti alloy was produced by solid state synthesis via mechanical alloying from elemental Ti and Ni powders. Using X-ray diffraction analysis and transmission electron microscopy techniques, a mechanically induced solid state reaction of 50Ni–50Ti was investigated. Results showed that nanocrystalline and amorphous Ni–Ti phases were obtained after mechanical alloying. The mechanical alloying of 50Ni–50Ti for 270 ks led to the formation of f.c.c. Ni(Ti) solid solution, characterized by a lattice parameter of 0.3558 nm, crystallite size of 14 nm and lattice strain of 0.98%. The particle size decreased with increasing milling time. The crystallite size of mechanically alloyed 50Ni–50Ti powders was substantially refined as the milling proceeded and the lattice strain increased with the milling time. The steady-state crystallite size was approximately 10–15 nm. The internal lattice strain in Ni–Ti alloy led to the disordering and the subsequent formation of amorphous alloy during mechanical alloying. After heat treatment at 1100 °C, the as-milled powders transformed into B2-NiTi phase and a small amount of Ti2Ni phase.