EW75镁合金高温扩散动力学研究  

High Temperature Diffusion Dynamics of EW75 Magnesium Alloy

作　　者：黄未华[1] 李兴刚[1] 张奎[1] 李永军[1] 马鸣龙[1] 张玉春 

机构地区：[1]北京有色金属研究总院有色金属材料制备加工国家重点实验室,北京100088 [2]西南铝业有限责任公司,重庆401326

出　　处：《稀有金属》2012年第1期13-18,共6页Chinese Journal of Rare Metals

基　　金：国家科技部十二五科技支撑项目(2011BAE22B01)资助

摘　　要：采用光学显微镜(OM)、扫描电子显微镜(SEM)和能谱分析(XRD),观察EW75合金大型铸锭原始态及高温热处理之后的组织及成分分布,以进行稀土元素在EW75合金中高温扩散动力学的研究。结果表明:EW75铸态合金中存在较为严重的局部偏析,大量非平衡凝固共晶组织在晶界处富集,Gd,Y,Nd在合金中的分布很不均匀,铸态组织呈大块的骨骼状,由α-Mg基体、Mg24Y5、Mg5Gd和Mg41Nd5非平衡凝固相组成,铸态合金晶粒尺寸约为100μm;在505及520℃保温24 h之后依然有较多未溶相残留在晶界上,由于温度稍微偏低,共晶组织未能完全溶解并分散到基体中;经过535℃,20 h高温热处理之后,共晶组织基本分解完全,稀土元素较为均匀地分布在基体中,晶粒长大非常明显;采用(EDS)分析测得各合金元素在EW75中的浓度分布,发现合金元素在EW75中成一定的规律分布,通过动力学方程计算得出了Y,Gd,Nd元素在不同温度下的lnδ-t关系曲线并进行线性拟合,最终得出Gd,Y,Nd在不同温度下的扩散系数。The microstructure evolution and composition of EW75 cast and homogenized alloy were studied by optical microscopy,scanning electron microcopy,energy dispersive spectrometer,to study the high temperature diffusion of rare earth elements in EW75 alloy.The results showed that serious dendrite segregation existed in the EW75 alloy ingot,and many non-equilibrium solidification eutectics enriched in the grain boundary.Gd,Y,Nd,elements distributed unevenly from the grain boundary to the side of the alloy,large as-cast organizations with skeletal shape were constituted by α-Mg,Mg24Y5,Mg5Gd and Mg41Nd5,and the grain size of as-cast alloy was about 100 μm.Many eutectics still exited in the grain boundary after HTT at 505,520 ℃ for 24 h as the temperature was too low.Most of the non-equilibrium eutectic phases dissolved after high temperature treatment（HTT） at 535 ℃ for 20 h,and all elements became more homogenized,but the grain size became large.The concentration distribution of all elements which distributed regularly were studied by EDS,and the relation curves of lnδ-t for Gd,Y,Nd in different temperature were calculated by using kinetic equation.Diffusion parameters were obtained by linear fitting finally.

关 键 词：EW75镁合金 高温热处理 扩散 动力学方程 

分 类 号：TG146.22[一般工业技术—材料科学与工程]