Solid State Amorphization Reaction in Cold-Rolled Ni/Ti Multilayers. 2. A Constant-Heating-Rate Annealing Treatment.

摘要

The Ni/Ti multilayers were produced through repeated cold rolling of coated Ni/Ti powder. The solid state amorphization reactions induced by a constant-heating-rate annealing in the multilayers were studied by means of X Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Differential Scanning Calorimetry (DSC) and magnetic analysis. Upon annealing at a constant heating rate, an amorphous phase initially forms in the multilayers. As the amorphous layer thickness exceeds a critical value, the intermetallic Ni3Ti and NiTi phases appear through the interdiffusion of elements. Finally, the formed amorphous phase crystallizes into the intermetallic compounds, Ni3Ti and Ti2Ni. A diffusion-controlled layer growth mechanism and a transient-nucleation model were used to calculate, for the first time, the grown amorphous layer thickness and the temperature of formation of intermetallic compounds for the Ni/Ti multilayers utilizing constant-heating-rate annealing.