Solidification Behavior of Mg-Zn and Mg-Zn-Zr Alloys Using In-Situ Neutron Diffraction

In-situ neutron diffraction was used to examine the solidification behaviors of Mg-Zn and Mg-Zn-Zr alloys by melting the alloy in a graphite crucible and irradiating the sample using monochromatic neutrons at 25 different temperatures as it solidified and cooled from 650 to 300 °C. The microstructure of the solidified Mg-Zn sample after in-situ neutron diffraction consisted of Zn-enriched Mg matrix and had an average grain size of ~1500 μm. The Mg-Zn-Zr alloy had a grain size of ~240 μm. The coarse grain size of the Mg-Zn alloy resulted in a large variation in neutron-scattering intensities between the (101¯0)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ ( 1 0 {{\bar{1}0)}} $$\end{document} and (101¯1)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ ( 1 0 {{\bar{1}1)}} $$\end{document} planes with the (0002)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ ( 0 0 0 2 ) $$\end{document} plane being absent, while the Mg-Zn-Zr alloy had the planes (101¯0)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ ( 1 0 {{\bar{1}0)}} $$\end{document}, (101¯1)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ ( 1 0 {{\bar{1}1)}} $$\end{document}, and (0002)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ ( 0 0 0 2 ) $$\end{document} which are all clearly represented. The authors determined that finer grain sizes improved counting statistics and that increasing sample dimensions or sample oscillation could further improve the diffraction results.