In-situ high temperature XRD studies and crystallization behavior of a Ti-rich Ti-Ni-Cu ribbon

Abstract

Structure evolution and crystallization behavior of initially amorphous Ti52Ni23Cu25 alloy ribbon were investigated by means of in-situ high temperature X-ray diffraction and DSC. The structure of crystallization products and the texture of B2 phase vary with annealing temperature increasing from 350 to 650°C. B2 crystalline phase was formed initially at 400°C from the amorphous ribbon, while a Ti2(Ni+Cu) type of precipitates were developed at the temperature above 550 °C. The texture of B2 phase has a transition from B2-(200) to B2-(011), and then keeps stable as the annealing temperature increases. Continuous DSC measurements with different heating rates were performed to determine crystallization activation energy and Avrami exponent for the alloy ribbon. The activation energy determined by Kissinger's equation was 372kJ/mol. The Avrami exponent values (n=2) obtained from the basis analysis of Johnson-Mehl-Avrami equation are consistent with diffusion controlled crystallization processes with decreasing nucleation rate.