Measurement of the Interdiffusion Coefficients in Mo-Ti and Mo-Ti-Zr Beta Phase Alloys from 1273 to 1473 K

Abstract

Accurate interdiffusion information is not only useful to determine alloy stability under long-term service conditions but also valuable in dealing with processing design. The work entailed an initial preparation of four beta phase Mo-Ti diffusion couples, which were used to determine the composition-dependent interdiffusivities at 1273, 1373, 1423 and 1473 K to validate the literature data and provide new experimental data over the whole composition range. Besides, utilizing 18 groups of bulk diffusion couples applied to EPMA technique, the composition dependence of ternary interdiffusion coefficients were obtained by using Whittle–Green method along with the uncertainty analysis for the obtained interdiffusion coefficients. The reliability of the experimental interdiffusivities is validated via thermodynamic constraints. Taking Ti as the solvent element, the present work indicates that in the temperature range between 1273 and 1473 K, the ternary interdiffusion coefficients increase by one order of magnitude per 100 K, and the diffusion of Zr is generally faster than that of Mo. The ternary main interdiffusion coefficients D~MoMoTi with different compositions of Zr at 1273, 1373, and 1473 K were compared with the values obtained for the boundary binary Mo-Ti system in both present experimental work and the literature. A composition-dependent decreasing-increasing tendency is observed for D~MoMoTi.