Mg-xZn-1Mn镁合金均匀化热处理及扩散动力学研究  

Homogenizing Heat Treatment and Diffusion Kinetics of Mg-xZn-1Mn Magnesium Alloy

作　　者：袁家伟[1] 李婷[1] 李兴刚[1] 张奎[1] 郝永辉[2] 罗广求[2] 

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]中国电子科技集团公司第十八研究所,天津300381

出　　处：《稀有金属》2012年第3期373-379,共7页Chinese Journal of Rare Metals

基　　金：国家"十二五"课题支撑计划(2011DAE22B01)资助项目

摘　　要：采用光学显微镜、扫描电镜、能谱分析、X射线衍射、布氏硬度测试等材料方法,研究了新型变形镁合金Mg-xZn-1Mn(x=4%,5%,6%,质量分数)的铸态合金以及均匀化热处理T4和时效处理T6后合金的显微组织、成分以及硬度的演变规律,建立ZM合金的热处理制度。并以空位扩散机制为基础,研究均匀化扩散动力学过程,建立ZM合金的均匀化扩散方程。结果表明:在ZM系列合金中,铸态组织枝晶偏析严重,晶界上有许多粗大的Mg-Zn共晶组织,Mn主要以单质形式存在于合金中。随着Zn含量的增加,合金的化合物体积分数增加,枝晶明显细化。得出3种合金合理的均匀化处理工艺分别是:ZM41为370℃×12 h;ZM51为390℃×12 h;ZM61为390℃×20 h。随着Zn含量的增加,热处理的温度和时间增加。在均匀化过程中,随均匀化处理温度提高,均匀化程度越高,时效硬化效果越好。经均匀化热处理后,大部分的Mg7Zn3相溶入基体。通过扩散动力学计算得到ZM41合金的均匀化处理温度与时间的关系为0.0008/t=exp(- 1160T9.5/T),570 K<T<670K,由此经验公式计算得出的均匀化处理制度与实验所得结果基本吻合。The microstructure,composition distribution and micro hardness of as-cast,homogenized（T4） and aged（T6） Mg-xZn-1Mn（x=4%,5%,6%,mass fraction） magnesium alloy were investigated by optical microscopy,hardness measurement,scanning electron microscopy,energy dispersive and X-ray diffraction,thus the homogenization parameters of ZM alloys were determined.Based on the vacancy diffusion mechanism,the diffusion kinetics and kinetic equations during the homogenizing heat treatment were investigated.The results indicated that the serious dendrite segregation existed in the as-cast ZM magnesium alloys,numerous coarse unequilibrium Mg-Zn eutectic microstructures existed in the grain boundary.The element Mn distributed mainly as pure Mn particles.With the Zn content increasing,the Mg-Zn phase volume fraction increased,and dendrite size decreased.The proper parameters of the alloys during homogenizing heat treatment were： ZM41：370 ℃×12 h,ZM51：390 ℃×12 h,ZM61：390 ℃×20 h,respectively.With the Zn content increasing,the homogenization temperature and time increased.Age hardening efficiency was better when homogenization temperature was higher.Most of the Mg7Zn3 phase dissolved after the alloy was homogenized.The kinetic equation of ZM41 alloy was 0.0008/t=exp（- 11609.5/T）in the temperature range from 570K to 670K.It had good agreement between the experiment results and the calculated one.

关 键 词：Mg-Zn-Mn镁合金 均匀化热处理 扩散动力学 

分 类 号：TG166.4[金属学及工艺—热处理]