Microstructural evolution of nanostructured Ti0.7Ni0.3N prepared by reactive ball-milling

Nanocrystalline stoichiometric Ti0.7Ni0.3N powder has been synthesized by ball-milling the α-Ti (hcp) and Ni (fcc) powders under N2 gas at room temperature. The α-Ti phase partially transforms to the transient (-Ti phase after 1 h of milling. After 5.5 h of milling, very broad reflections of Ti0.7Ni0.3N phase is noticed. Complete formation of Ti0.7Ni0.3N phase is observed after 9 h of milling. Microstructure in terms of lattice imperfections of unmilled and all ball-milled powder mixtures are primarily characterized by analyzing the X-ray powder diffraction patterns employing the Rietveld structure refinement procedure. It clearly reveals the presence of Ti0.7Ni0.3N phase and inclusion of nitrogen atoms into the α-Ti–Ni matrix on the way to formation of nitride phase. Microstructure of the ball milled nitride powders is also characterized by HRTEM. Particle size of Ti0.7Ni0.3N phase obtained from XRD method of characterization is ∼5 nm which is very close to that obtained from HRTEM.