薄板5B70铝合金TIG焊缝熔池组织细化特征  

Micro-structure Refine Characteristics of 5B70 Al Alloy Sheet Welded Joints by TIG Welding

作　　者：田志杰 刘焱 尚傲霜 杜晗 郝双喜 TIAN Zhijie;LIU Yan;SHANG Aoshuang;DU Han;HAO Shuangxi(Capital Aerospace Machinery Co.,Ltd.,Beijing,100076)

机构地区：[1]首都航天机械有限公司,北京100076

出　　处：《导弹与航天运载技术(中英文)》2025年第1期85-90,共6页Missiles and Space Vehicles

基　　金：国防基础科研计划项目(JCKY2023903A001);湖南省科技重大专项(2021GK10402)。

摘　　要：以5B71合金焊丝为填充材料,采用钨极惰性气体(Tungsten Inert Gas,TIG)保护焊接工艺对1.5 mm厚5B70铝合金板材进行焊接,对焊接接头进行显微组织演变及细化特征的研究。结果表明:采用合理的焊接参数,可得到成形优良的焊接接头,焊缝内部组织显示,焊缝区主要是由等轴晶组成的铸造组织,晶粒组织大小不均匀,广泛存在着40~50μm大小的晶粒,也存在着以细条状和小块状分布、直径大小约20μm的超细晶区,超细晶区域面积明显小于其他区域,主要沿着平行于熔合线的方向分布,少量分布在焊缝表面。熔池凝固过程中,钪(Sc)和锆(Zr)元素对晶粒细化作用明显,Sc元素富集的区域,晶粒细化程度愈高。在熔合线及焊缝表面,Sc和Zr作为生成变质剂元素,可析出第二相粒子,起到非均匀形核质点的作用,降低形核功,增加晶粒数量,Sc元素富集的区域,晶粒细化程度愈高。固液界面前沿形成“过冷区”,促进等轴晶形成,晶粒进一步细化,晶粒尺寸减小约一半。A 5B70 aluminum alloy sheet with 1.5 mm thickness is welded by tungsten inert gas(TIG)welding with 5B71 filler wire.The micro-structure evolution and refinement characteristics of the welded joints are investigated.The research results indicated that weld joints with excellent formation can be obtained by adopting reasonable welding parameters.The internal structure of the weld seam shows that the weld zone is mainly composed of equiaxed crystals forming a cast structure,the size of the grain structure is uneven,there are widely larger grains with a diameter of 40~50μm,as well as ultrafine grain areas with a diameter of about 20μm which distributes in fine strips and small blocks.The area of the ultrafine grain region is obviously smaller than other areas.It mainly distributes in the direction parallel to the fusion line,with a few distributed on the weld surface.Sc and Zr were used as modificator to refine the grains.The Al3(Sc,Zr)second phase particles are precipitated in the welding pool during solidification.The function of such particle is to form heterogeneous nucleation particles,reduce nucleation power and increase the number of crystal nuclei.The area where Sc elements are enriched had a higher degree of grain refinement.The"undercooling"zone is formed along the front of the solid-liquid boundary,which promotes the formation of equiaxed grains.It results in a higher degree of grain refinement,which size is only about one half of other zones.

关 键 词：5B70铝合金 钨极惰性气体 微观组织 晶粒 焊接 

分 类 号：TG442[金属学及工艺—焊接] V46[航空宇航科学与技术—航空宇航制造工程]