Phase equilibria and diffusion coefficients in the Fe-Zn binary system. (March 2020)

• Record Type: Journal Article
• Authors: Zhu, Lilong; Honrao, Shreyas; Rijal, Biswas; Hennig, Richard G.; Manuel, Michele V.
• Is Part Of: Materials & design. Volume 188(2020)
• Publication Date: 2020-03
• Subjects: Fe-Zn system -- Coating -- Fe/Zn LSDCs -- Phase equilibria -- Diffusion coefficients -- DFT calculations; Materials -- Periodicals; Engineering design -- Periodicals; Matériaux -- Périodiques; Conception technique -- Périodiques; Electronic journals; 620.11
• DOI: 10.1016/j.matdes.2019.108437
• Languages: English
• ISSNs: 0264-1275

Abstract

Abstract: Phase diagram and diffusion coefficients of the Fe-Zn binary system are required to predict and control the microstructure of galvanized zinc coatings and thus were systematically investigated in the temperature range from 700 to 1100 °C using nine novel Fe/Zn liquid-solid diffusion couples (LSDCs). The equilibrium compositions of the α and Γ phases of the Fe-Zn system were determined and agree well with the recently established Fe-Zn phase diagram. The extracted interdiffusion coefficients in α-Fe at temperatures between 700 and 1100 °C and in Γ at 750 and 700 °C using the forward-simulation analysis (FSA) extend the experimental interdiffusivity measurements to the whole solubility range of these two phases. Three impurity diffusion coefficients of Zn in paramagnetic α-Fe were also determined by the FSA and show good agreement with the literature data. The temperature dependence of the Zn impurity diffusion coefficients in both the paramagnetic and ferromagnetic α-Fe phases across the Curie temperature T C was established by analyzing the reliable experimental results as well as by density functional theory (DFT) calculations. The newly measured phase equilibrium and diffusivity data provide reliable inputs for future thermodynamic and kinetic modeling of the Fe-Zn system. Graphical abstract: Unlabelled Image Highlights: Phase equilibria and diffusion coefficients in the Fe-Zn system were investigated using Fe/Zn liquid-solid diffusion couples. Seventeen reliable equilibrium compositions of the α-Fe and Γ phases between 700 and 1100 °C were determined. Interdiffusion coefficients in α and Γ were extracted over the entire solubility range using forward-simulation analysis. Temperature dependence of Zn impurity diffusion coefficients in both ferromagnetic and paramagnetic α-Fe was established. DFT calculations using different exchange-correlation functionals were performed to study Zn impurity diffusion in α-Fe.