Measurement of Diffusion Coefficients in the bcc Phase of the Ti-Sn and Zr-Sn Binary Systems

Abstract

Sn and Zr are two important alloying elements in low-modulus biomedical titanium alloys, yet experimental data on Sn diffusion in bcc Ti and bcc Zr are still very limited in the literature, and thus were systematically measured in the present study using solid–solid diffusion couples (SSDCs) and novel liquid–solid diffusion couples (LSDCs). Both interdiffusion and impurity diffusion coefficients in the bcc phase of the Ti-Sn and Zr-Sn systems were extracted with forward-simulation analysis (FSA), and show good agreement with existing literature. The interdiffusion coefficients in the Ti-Sn system at six temperatures, from 950 °C to 1200 °C, extend experimental measurements to a much wider composition range, and the interdiffusion coefficients in the Zr-Sn system at 1200 °C, 1150 °C, and 1100 °C are the first such data experimentally measured. The data obtained from this study, together with our previous data for the Ti-X (X = Cr, Hf, Mo, Nb, V, Zr) systems, provide reliable experimental inputs to improve the mobility databases for advanced Ti alloys development. In addition, the excellent agreement between the LSDCs and SSDCs results validates the reliability of this novel approach by combining LSDC experiments and FSA in evaluating diffusion coefficients at elevated temperatures.