Interdiffusion and Atomic Mobility in BCC-A2 Mo-Zr and Mo-Nb-Zr Alloys with Very Steep Composition Profiles

Abstract

Combination of the experimental measurements of diffusion behavior and kinetic computational simulation provides a unique tool to probe the design of multi-component refractory alloys with excellent properties. In this work, for the first time, the determination of the interdiffusion coefficients of bcc phase in Mo-Zr system and Mo-Nb-Zr ternary system as well as the relevant atomic mobility parameters of Mo, Nb and Zr in BCC phase are investigated systematically. The interdiffusion coefficients of bcc phase in Mo-Zr binary alloys and Mo-Nb-Zr ternary alloys at 1423-1523 K were measured by solid-phase diffusion couple method combined with Boltzmann-Matano method and Matano-Kirkaldy method, respectively. Simultaneously, the quite steep Mo concentration gradients of the corresponding ternary diffusion couples in the Mo-Nb-Zr system are observed in this study, and the contributions of which are carefully evaluated in the subsequent extraction of the ternary interdiffusion coefficients for the Mo-Nb-Zr system. On the basis of the determined interdiffusion coefficients of Mo-Zr system and Mo-Nb-Zr system in this work, along with the relevant thermodynamic parameters, the atomic mobility parameters of Mo, Nb and Zr in BCC phase were evaluated, which are incorporated into the atomic mobility database of bcc phase in Nb-Mo-Ti-Zr multi-component system. In addition, the component distance curves of a series of diffusion couples are simulated by applying the established atomic mobility database. The consistency between the simulated results and the measured values further verifies the reliability of the work.