A new experimental result indicating 3 separate phase fields of ε, ε1, ε2 and the estimation of diffusion coefficients in the Mn–Zn system

Abstract

The Mn–Zn system, technologically crucial for galvanized Mn–containing steels and potential ZnMn–based biomaterials, has been studied using the conventional diffusion couple technique. The first experimental evidence has been presented to indicate the presence of 3 separate phases, as $\epsilon$, $\epsilon$₁ and $\epsilon$₂, together in the interdiffusion zone. By taking advantage of local equilibrium present at interphase interfaces in a diffusion couple, the controversial $\epsilon$–phase region has been resolved after almost more than 6 decades. Incorporating new experimental results of 3 separate phases could be beneficial in refining the present thermodynamic optimization of the Mn–Zn system. Furthermore, MnZn₉ and MnZn₁₃ have also grown in the Mn/Zn diffusion couple, such that there are 5 distinct phase layers, including $\epsilon$, $\epsilon$₁ and $\epsilon$₂. Diffusion parameters such as integrated diffusion coefficients and the ratio of tracer diffusivities, which are currently unavailable, are also determined considering ideal molar volumes. It helps to understand the atomic mechanism of diffusion and the probable defects present in phase(s).