Gd对Mg-5Si合金组织和力学性能的影响  

Effect of Gd Modification on Microstructure and Mechanical Properties of Hypereutectic Mg-5Si Alloy

作　　者：刘辉[1] 尧军平[1] 张磊[1] 

机构地区：[1]南昌航空大学航空制造工程学院

出　　处：《特种铸造及有色合金》2015年第9期999-1002,共4页Special Casting & Nonferrous Alloys

基　　金：国家自然科学基金资助项目(51164027);江西省教育厅2012年度科技计划资助项目(GJJ12432);南昌航空大学第八届"三小"科技创新基金资助项目

摘　　要：采用Mg-30Gd中间合金对过共晶Mg-5Si合金进行变质处理,考察了Gd对合金组织与力学性能的影响,并讨论了其变质机理。结果表明,Gd对过共晶Mg-5Si合金中初生Mg2Si相具有良好的变质作用。当加入2.0%的Mg-30Gd时,变质效果最佳,初生Mg2Si相的平均尺寸减小到25μm以下,其形态大部分为近球状,并且分布均匀,合金的抗拉强度和伸长率也达到了最大值,分别为105 MPa和3.1%。但是,当Mg-30Gd增加到3.0%时,初生Mg2Si相又转变为粗大的树枝晶形态。变质机理与稀土元素富集于初生Mg2Si相生长表面抑制优先生长晶向的生长,以及金属间化合物GdxSiy为初生Mg2Si相生长提供了异质形核核心有关。The modification effect of rare earth Gd on primary Mg2Si in hypereutectic Mg-5Si alloy was analyzed, meanwhile, effects of Gd on microstructure and mechanical properties of the alloy were presented, and modification mechanism was described. The results reveal that Gd exhibits desirable modification effects on primary Mg2Si phase in the hypereutectic Mg-5Si alloy, especially 2.0% Mg-30Gd addition. The average size of primary Mg2Si phase can be decreased to less than 25 tam, and the morphology of primary Mg2 Si phase is transformed from the coarse dendrite into fine polyhedron particle with more uniform distribution. The tensile strength and elongation of the alloy reach 105 MPa and 3.1%, respectively. However, with the Mg-30Gd content more than 3.0%, the primary Mg2Si phase in the hypereutectic Mg-5Si alloy is coarsen again. The refinement of Gd is mainly associated with the enrichment of Gd on the growth facets of the primary Mg2Si crystals to depress the preferred crystal growth. In addition, intermetallic compound GdxSiy can be taken as heterogeneous nuclei of the primary Mg2Si phase growth.

关 键 词：稀土Gd 过共晶Mg-5Si合金 初生Mg2Si 变质处理 

分 类 号：TG146.22[一般工业技术—材料科学与工程] TG113.25[金属学及工艺—金属材料]