铸造Al-Zn-Mg-Cu-Zr-Sc合金热处理析出相转变及其对力学性能的影响  

Transformation of Precipitates in the As-cast Al-Zn-Mg-Cu-Zr-Sc Alloys during Heat Treatment and Their Effects on Mechanical Properties

作　　者：周殿买 范军 韩庆利 李家衡 张英波[2] 徐彬[3] ZHOU Dian-mai;FAN Jun;HAN Qing-li;LI Jia-heng;ZHANG Ying-bo;XU Bin(CRRC Changchun Railway Vehicle Co.,Ltd.,Changchun 130051,China;Key Laboratory of Advanced Technology for Materials,Ministry of Education,Southwest Jiaotong University,Chengdu 610031,China;Changchun Automobile Industry Institute,Changchun 130013,China)

机构地区：[1]中车长春轨道客车股份有限公司,长春130051 [2]西南交通大学材料先进技术教育部重点实验室,成都610031 [3]长春汽车工业高等专科学校,长春130013

出　　处：《精密成形工程》2022年第4期146-153,共8页Journal of Netshape Forming Engineering

基　　金：中国国家铁路集团系统性重大项目(P2020J04)。

摘　　要：目的为满足高速列车关键部件的轻量化需求,开发高性能铸造铝合金。方法熔炼铸造了低锌、低镁且含微量钪的Al-5.78Zn-1.63Mg-1.75Cu-0.17Zr-0.22Sc(质量分数)合金,对合金实施了双级均匀化处理及“固溶+时效”(T6)工艺,结合光镜(OM)、X射线衍射仪(XRD)、扫描电镜(SEM)、能谱仪(EDS)及透射电镜(TEM)多种分析测试手段,对比研究合金在铸态、均匀化态及T6处理态下的微观组织特征,重点关注了析出相的演变,并通过室温拉伸性能实验测试合金的力学性能。结果铸态合金中的析出相以粗大的Mg(Zn,Cu,Al)_(2)相为主,且分布于晶界或枝晶界,在室温拉伸过程中粗大的Mg(Zn,Cu,Al)_(2)相割裂基体,造成合金在弹性变形阶段的脆断,基本无伸长率;双级均匀化处理后,晶界及枝晶间的第二相明显减少,晶内析出了大量的针状相Mg(Zn,Cu,Al)_(2),而T6处理后,晶内针状相基本消失,时效过程中析出以η’-MgZn_(2)相为主的高密度弥散分布纳米析出相,其平均尺寸为(9.2±0.9)nm,相比于铸态,T6处理后合金的抗拉强度从417 MPa提高到577 MPa,且展现出一定的伸长率。结论T6处理后合金中析出相由粗大的针状相转变为高密度弥散分布纳米析出相,该析出相可在变形过程中有效钉扎位错,从而提高合金力学性能。The work aims to develop a high-performance cast aluminum alloy,so as to meet the further lightweight requirement of key components of high-speed train.An as-cast Al-5.78Zn-1.63Mg-1.75Cu-0.17Zr-0.22Sc(wt.%)alloy with low zinc(Zn),low magnesium(Mg)and scandium(Sc)was melted.The alloy was engaged in the treatment of the two-stage homogenization and"solution+aging"(T6).The optical microscope(OM),X-ray diffraction(XRD),scanning electron microscopy(SEM),energy spectrometer(EDS),transmission electron microscopy(TEM)and tensile test were used to investigate the microstructure characteristics of as-cast,as-homogenized and as-T6-treated alloy,focusing on the evolution of precipitates,and the mechanical properties of the alloy were tested by tensile test at room temperature.The major precipitates in the as-cast alloy were coarse Mg(Zn,Cu,Al);,which distributed along the grain boundaries or dendritic grain boundaries and split the as-cast matrix during the tensile test,causing the brittle fracture in the elastic deformation stage with almost no elongation.After two-stage homogenization,the second phase in grain boundary and interdendrite decreased significantly,and amounts of needle-like Mg(Zn,Cu,Al);were precipitated inside the grains.After T6 treatment,the needle-like precipitates inside the grains disappeared and high-density dispersed nanoscale precipitates dominated byη’-MgZn;phase with an average size of(9.2±0.9)nm appeared during aging.Then,compared with the as-cast alloy,the as-T6-treated alloy exhibited an improved tensile strength from 417 MPa to 577 MPa,and possessed a certain elongation as well.After T6 treatment,the precipitates transform from coarse needle-like phase to high-density dispersed nanoscale phase,which can effectively pin the dislocations during the deformation process,thus improving the mechanical properties of the alloy.

关 键 词：Al-Zn-Mg-Cu-Zr-Sc合金 热处理 析出相 力学性能 

分 类 号：TG146.21[一般工业技术—材料科学与工程]