Atomic mobilities and diffusivities in the bcc phase of Ti–Nb–Sn system

Abstract

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