添加Si和Zn对VW75镁合金显微组织、力学性能和弹性模量的影响  

Microstructure,Mechanical Properties and Elastic Modulus of VW75 Magnesium Alloy with Si and Zn Addition

作　　者：张驰 石国梁 张奎[1,2,3] 李兴刚 李永军[1,2,3] 马鸣龙 Zhang Chi;Shi Guoliang;Zhang Kui;Li Xinggang;Li Yongjun;Ma Minglong(State Key Laboratory of Nonferrous Metals and Processes,China GRINM Group Co.,Ltd.,Beijing 100088,China;GRIMAT Engineering Institute Co.,Ltd.,Beijing 100088,China;General Research Institute for Nonferrous Met-als,Beijing 100088,China)

机构地区：[1]中国有研科技集团有限公司有色金属材料制备加工国家重点实验室,北京100088 [2]有研工程技术研究院有限公司,北京101407 [3]北京有色金属研究总院,北京100088

出　　处：《稀有金属》2024年第6期796-807,共12页Chinese Journal of Rare Metals

基　　金：江苏省科技厅项目(BA2017044);有研集团科技创新基金战略研究项目(2019DY01050)资助。

摘　　要：Mg-7Gd-5Y-1Nd-0.5Zr (%,质量分数;VW75)是一种获得批量应用的超高强耐热镁合金,但其弹性模量仅约为45 GPa,制约了其减重效果的充分发挥。以提升该合金弹性模量为目的设计了3种成分合金:VW75+1Si, VW75+2Si和VW75+2Si+2Zn(%,质量分数),利用光学显微镜(OM)、扫描电镜(SEM)、 X射线衍射(XRD)等研究了“铸锭→均匀化→挤压”过程的显微组织演变,研究了3种合金在200℃的时效硬化行为,并对挤压态和T5态合金的室温拉伸性能和动态弹性模量进行了测试。结果表明:VW75合金添加Si后在熔体中形成高熔点自生增强相颗粒,增强相存在严重的沉降现象。XRD分析表明增强相为Gd_(5)Si_(3), YSi和Zr_(5)Si_(3),并且多数RE-Si(RE:稀土元素)增强相颗粒同时具有两个成分迥异的区域,即心部的富Y区和外层的富Gd区,暗示熔体降温过程中YSi先形核,Gd_(5)Si_(3)随后以YSi为异质核心析出,添加Zn元素加重了沉降。3种铸态合金中增强相平均粒径位于3.8~5.5μm区间,挤压后被破碎细化至3.4~3.7μm,且分布更加均匀。制备的3种合金中,VW75+2Si+2Zn合金铸态、挤压态和T5态弹性模量最高;挤压态VW75+2Si+2Zn合金具有最大的增强相面积分数(~9.4%)且增强相平均粒径仅~3.5μm,其T5(挤压+人工时效)态弹性模量最高,达到53.4 GPa,但由于RE-Si增强相的出现严重弱化了稀土元素的固溶强化作用,造成抗拉强度和屈服强度大幅降低,同时造成该合金没有时效硬化效应。Magnesium alloys are the smallest density metal structural materials in the world today.They have great application pros⁃pects in the fields of aerospace weapons and equipment.In recent years,the speed of aerospace weapons and equipment is higher and higher and the range is longer and longer.Therefore,higher requirements are put forward for the stability and lightweight of load-bear⁃ing parts.At present,Mg-RE-Zn(RE:rare earth)magnesium alloy has excellent mechanical properties at room temperature and high temperature,and the tensile strength at room temperature can reach more than 450 MPa,and it is one of the most potential materials for manufacturing missile cabin and rudder wing surface.However,the elastic modulus of Mg-RE-Zn alloy is very low,only 40~45 GPa,far lower than that of aluminium alloy(70 GPa),titanium alloy(110 GPa)and steel(206 GPa),and the problem of"strength modu⁃lus"mismatch appears in the service state of high stress.In order to improve the anti-elastic deformation ability of missile cabin and rudder wing surface,the commonly used method is to increase the section thickness,but this method increases the overall weight of the equipment and seriously restricts the improvement of flight speed and range of aerospace weapon equipment.Therefore,the de⁃mand for high elastic modulus magnesium alloy is becoming more and more urgent.This paper took Mg-7Gd-5Y-1Nd-0.5Zr(%,mass fraction;VW75)magnesium alloy as the research object,and studied the microstructure changes,mechanical properties and elastic modulus of three alloys with different contents,revealing the influence of Si and Zn contents of three alloys.The microstructure of as cast,homogenized and extruded phases were observed and analyzed by metallographic microscope(OM)and scanning electron micro⁃scope(SEM),and the chemical composition of various phases was analyzed by energy dispersive spectrometer(EDS)attached to SEM.Xpert Pro MPD polycrystalline X-ray diffractometer(XRD)was used to analyze the as cast and homogeneous microstructure at

关 键 词：镁合金 增强相 显微组织 力学性能 弹性模量 

分 类 号：TG146.2[一般工业技术—材料科学与工程]