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Indexed by:期刊论文

Date of Publication:2018-07-01

Journal:JOURNAL OF MATERIALS SCIENCE & TECHNOLOGY

Included Journals:SCIE

Volume:34

Issue:7

Page Number:1132-1141

ISSN No.:1005-0302

Key Words:Mg-Gd solid solution; Cluster-plus-glue-atom model; Solute-homogenization model; Mg-Gd-Y-Zr cast alloys

Abstract:Composition homogenization in solid solution is important for industrial alloys. In the present work, a solute homogenization model is proposed based on the chemical short-range-order tendency in Mg-Gd-based alloys. After a calculation using the cluster-plus-glue-atom model, the stable Mg-Gd structural unit is derived, [Gd-Mg-12]Mg-6, where one solute Gd is nearest-neighbored with twelve Mg atoms to form the characteristic hcp cluster [Gd-Mg-12] and this cluster is matched with six Mg glue atoms. Such a local unit is then mixed with [Mg-Mg-12]Mg-3, the stable unit for pure Mg. Assuming that the Gd-containing units are arranged in fcc- or bcc-like lattice points and the Mg units in their octahedral interstices, three proportions between the two units are obtained, 1:1, 2:3, and 1:3, which constitute three solute homogenization modes. The prevailing Mg-Gd-based alloys are consequently classified into three groups, respectively exemplified by GW103 K (Mg-10Gd-3Y-0.4Zr, wt%), GW83 K (Mg-8Gd-3Y-0.4Zr), and GW63 K (Mg-6Gd3Y-0.4Zr). Mg-Gd-Y-Zr alloys were designed following the model (where Y and Zr were also added in substitution for Gd) and prepared by permanent-mould casting. According to their mechanical properties, the 1:3 alloy (Mg-5.9Gd-1.6Y-0.4Zr) shows the best comprehensive properties (ultimate tensile strength 305 MPa, yield strength 186 MPa, elongation 9.0%) in solution plus ageing state. (C) 2017 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.