Phase equilibria, crystal structure of δ1-MnZn9 and thermodynamic re-assessment of the Zn-Mn system

Highlights: • The phase equilibria of the Zn-Mn system in the Zn-rich side Zn-rich at 400 °C was obtained. • The space group of the δ₁-MnZn₉ phase was determined to be P6₃/mmc. • A set of self-consistent thermodynamic parameters for the Zn-Mn system was obtained by the CALPHAD approach. • The reliability of the thermodynamic parameters was verified by the Scheil solidification simulation. -- Abstract: The phase relationship of the Zn-Mn system in the range of 0–12 at% Mn at 400 °C was experimentally investigated. Four phases, viz, ε, δ₁-MnZn₉, ζ-MnZn₁₃ and (Zn) were observed in the present work. The δ₁-MnZn₉ phase was determined to be a hexagonal structure (space group P6₃/mmc, No. 194, lattice parameters: = b = 1.2771 Å, c = 5.7069 Å) based on the single-phase X-ray diffraction data and confirmed by the analysis of the high-resolution image and selected area electron diffraction. Presently obtained experimental results, combined with the reliable literature data, were used to develop a refined thermodynamic description of the Zn-Mn system utilizing the CALPHAD (CALculation of PHAse Diagram) method. The present calculated results can reproduce the experimental data well. The reliability of the presently obtained thermodynamic parameters was also verified by the Scheil solidification simulation and phase analysis of the as-cast alloys.