Quantitative Study of Microstructure-Dependent Thermal Conductivity in Mg-4Ce-xAl-0.5Mn Alloys
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The effect of microstructure on thermal conductivity was investigated for Mg-4Ce-xAl-0.5Mn (x = 0 to 6 wt pct) alloys produced by gravity casting and high-pressure die casting. The solidification microstructure of the alloys was quantitatively studied using CALculation of PHase Diagrams (CALPHAD) modeling and experimental characterization. The lattice volume of Mg solid solution was measured via X-ray diffraction (XRD) method. The results show that the thermal conductivity is influenced mostly by lattice volume, and, to a lesser extent, by intermetallic compounds. Also, thermal conductivity has a strong negative correlation with the concentration of total solute atoms. When the addition of Al is less than 3 wt pct, the thermal conductivity of die casting alloys with higher cooling rate and solute concentration is lower than that of gravity casting alloys. However, their thermal conductivities tend to be equal when the Al addition exceeds about 3 wt pct, as the concentration of solute atom is approaching the solid solubility limit. Two methods (structural model and Wiedemann–Franz law) were proposed and modified to predict their thermal conductivities, respectively. Both can provide a good prediction of thermal conductivity values.
The authors acknowledge the funding for the National Key R&D Program (No. 2016YFB0301002) supported by the Ministry of Science and Technology of China and the Major Science and Technology projects in Qinghai province (2018-GX-A1). This work was co-funded by the National Natural Science Foundation of China (Nos. 51301107, 51601111). C. Su would also like to express his gratitude to China Scholarship Council for supporting his stay at The Ohio State University as a visiting scholar. D. Li acknowledges the financial support received from Shanghai Jiao Tong University through SMC-Young scholar program.
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