5%Al合金化对Mg-6Zn镁合金非枝晶组织演变的影响  

Effects of 5%Al alloying on non-dendritic microstructure evolution of Mg-6Zn magnesium alloy

作　　者：张玉 李明 杨文龙 王宗刚[1,2] 王学志[1,2] 王琦山 ZHANG Yu;LI Ming;YANG Wen-long;WANG Zong-gang;WANG Xue-zhi;WANG Qi-shan(College of Physics and Electromechanical Engineering,Hexi University,Zhangye 734000,China;Institute of Advanced Material Forming Technology,Hexi University,Zhangye 734000,China)

机构地区：[1]河西学院物理与机电工程学院,甘肃张掖734000 [2]河西学院先进材料成形技术研究所,甘肃张掖734000

出　　处：《材料热处理学报》2020年第6期7-14,共8页Transactions of Materials and Heat Treatment

基　　金：河西学院博士科研启动基金;河西学院校长基金(XZ2018014)。

摘　　要：利用光学显微镜(OM)、扫描电镜(SEM)和X射线衍射仪(XRD)研究了Mg-6Zn和Mg-6Zn-5Al合金(质量分数)的铸态组织和等温热处理后非枝晶组织的演变规律。结果表明:Mg-6Zn合金的铸态组织主要由α-Mg和MgZn2相组成;Mg-6Zn-5Al合金铸态组织主要由α-Mg、Mg2Zn3、Mg17Al12和Mg32(Al,Zn)49相组成,其共晶组织形貌演变成粗大连续,且晶内颗粒状的第二相粒子数量增加。Mg-6Zn-5Al合金经600℃保温30 min后获得了细小圆整、均匀分布的近球状颗粒,其平均尺寸和圆整度分别为75μm和1.09。非枝晶组织演变的主要机制包括共晶组织熔化,溶质原子扩散,枝晶组织的粗化、分离、球化和颗粒的合并与长大。5%Al合金化促进了Mg-6Zn合金的非枝晶组织演变,主要归于合金化使铸态组织中析出了亚晶界,其为溶质原子的扩散提供便捷通道和润湿驱动力,同时降低了体系的总自由能和异质形核功,使合金在成分起伏和能量起伏作用下加快了枝晶组织的熔断、分离和球化。The as-cast microstructure of Mg-6 Zn and Mg-6 Zn-5 Al alloys(mass%),and their non-dendritic microstructure evolution during isothermal heat treatment were studied by means of optical microscope(OM),scanning electron microscopy(SEM)and X-ray diffractometer(XRD).The results show that the as-cast microstructure of the Mg-6 Zn alloy is mainly composed ofα-Mg and MgZn2 phases,and the as-cast microstructure of the Mg-6 Zn-5 Al alloy is mainly composed ofα-Mg,Mg2Zn3,Mg17Al12 and Mg32(Al,Zn)49 phases,the morphology of eutectic microstructure of the Mg-6 Zn-5 Al alloy evolves into coarse and continuous,and the number of granular second phase particles in the grain increases.The fine,round and evenly distributed near-spherical particles with average size of 75μm and roundness of 1.09 of the Mg-6 Zn-5 Al alloy are obtained after isothermal heat treatment at 600℃ for 30 min.The main mechanisms of non-dendrite microstructure evolution include eutectic microstructure melting,solute atom diffusion,coarsening,separating and spheroidization of dendrite microstructure,and particles merging and growth.5%Al alloying promotes the non-dendritic microstructure evolution of the Mg-6 Zn alloy,which is mainly attributed to the precipitation of sub-boundary in the as-cast microstructure,which provides convenient channel and wetting driving force for the diffusion of solute atoms,and reduces the total free energy and heterogeneous nucleation work of the system,and then accelerates the fusing,separation and spheroidization of the dendrite structure under the action of component fluctuation and energy fluctuation.

关 键 词：Mg-6Zn镁合金 Al合金化 等温热处理 演变机制 亚晶界 

分 类 号：TG146.2[一般工业技术—材料科学与工程]