Solute-homogenization model and its experimental verification in Mg-Gd-based alloys

• 来源期刊: 材料科学技术（英文版）
• 年，卷（期）: 2018,（7）
• 页码范围: 1132-1141
• 页数: 10页
• 语种: 英文

摘要

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-Mg12]Mg6,where one solute Gd is nearest-neighbored with twelve Mg atoms to form the characteristic hcp cluster [Gd-Mg12] and this cluster is matched with six Mg glue atoms.Such a local unit is then mixed with [Mg-Mg12]Mg3,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-6Gd-3Y-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.