Comparative studies of grain refinement of commercial purity Mg by CaO and Ca addition |
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| Authors: | YC Gu GS Song J Huang Y Wang SY Chen |
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| Affiliation: | 1. Key Laboratory of Green Manufacturing and Surface Technology of Advanced Metal Materials, Ministry of Education, School of Materials Science and Engineering, Anhui University of Technology, Ma’anshan, P. R. China;2. The EPSRC Centre-LiME, BCAST, Brunel University, Uxbridge, UK;3. State Key Laboratory of High Performance Complex Manufacturing, Central South University, Changsha, China |
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| Abstract: | ABSTRACTThe comparative studies of grain refinement of commercial purity Mg by CaO/Ca addition have been investigated by using TP-1 tests, optical microscope, XRD characterisation and TEM (STEM) observation along with EDX analysis. Experimental results showed that Ca/CaO addition significantly refines the grain structure of commercial purity Mg. Compared with Ca addition, CaO exhibits finer grain size and the average grain size remains invariable with further CaO addition. CaO addition is readily reduced to Ca by Mg melt and forms Mg2Ca on the surface of MgO particles. First-principle calculations were used to understand the nucleation of Mg2Ca layer by a coherent interface model calculating the work of adhesion and the interface energy between Mg2Ca and α-Mg. The combination of experiments and calculations showed that the formation of Mg2Ca layer on MgO facilitates the nucleation of α-Mg and then refines the grain structure by Ca or CaO addition. |
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| Keywords: | Heterogeneous nucleation magnesium grain refinement Ca CaO |
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