Atomic Mobilities and Diffusivities in the Bcc Phase of Ti-Nb-Sn Systems

Abstract

Accurate interdiffusion information is essential to control the phase transformation process in metastable β-type titanium alloys. In this work, diffusion behavior in ternary Ti-Nb-Sn system at 1373K and 1473K was experimentally investigated. The ternary interdiffusion coefficients and impurity diffusion coefficients in bcc Ti-Nb-Sn alloys were determined using the diffusion couple technique, along with the Whittle-Green ang Hall methods. Based on the obtained diffusion coefficients, an atomic mobility database for bcc Ti-Nb-Sn system was established via CALPHAD (CALculation of PHAse Diagrams) method. In the optimizing procedure, the end member and the binary parameters for bcc-Ti-Sn system were reassessed. The calculated results using the obtained database were compared with the experimental diffusion properties (i.e., interdiffusion, composition-distance profiles and diffusion paths), demonstrating the accuracy and effectiveness of the database developed in this work.

Keywords: atomic mobility, diffusion coefficient, bcc Ti-Nb-Sn alloys, CALPHAD modeling