77A09铝合金电子束焊接接头的显微组织与力学性能

Microstructure and Mechanical Properties of 7A09 Aluminum Alloy Electron Beam Welded Joint

采用电子束焊方法对7A09铝合金进行焊接,分析不同焊接工艺对接头显微组织与力学性能的影响,获得了焊缝表面成形良好的焊接接头。为了进一步改善接头区域的显微组织,以提高接头的力学性能,对接头进行焊后热处理。接头微观分析显示,焊态下接头熔合区由柱状晶和等轴状枝晶组成,初生相在晶界处聚集,形成共晶组织。在焊接过程中添加圆形电子束扫描,可改善接头焊缝成形,细化焊缝晶粒。接头经过焊后热处理,晶界初生相减少,较多的强化相η′(MgZn2)等在接头焊缝区析出。力学性能测试表明,热处理后接头的拉伸强度达400.6 MPa,为母材拉伸强度的80.8%。拉伸断口扫描观察显示,接头断口表面分布有许多大且深的韧窝,呈明显的韧性断裂特征。

7A09 aluminum alloy is welded by using electron beam welding.The effects of different welding processes on the microstructure and mechanical properties of the welded joints are investigated,and a well-formed joint is obtained.In order to further improve the microstructure of the weld zone and improve the mechanical properties of the welded joint,post-weld heat treatment(PWHT)is carried out.The microstructure analysis of the welded joint shows that in as-welded(AW)condition,the fusion zone(FZ)is composed of columnar crystal and equiaxed grains,and the primary phases aggregate at the grain boundary to form eutectic structure.During welding,adding circular electron beam scanning can improve the weld the formation and refine the grains in the weldment.After PWHT,the primary phases at the grain boundary are decreased,and many strengthening phases such asη('MgZn2)are precipitated in the weld zone.The mechanical property test shows that the tensile strength of the welded joint reaches 400.6 MPa after PWHT,which is 80.8%of that of the base metal.SEM images of tensile fracture demonstrate that there are many large and deep dimples on the fracture surface,and the joint obviously presents the characteristics of ductile fracture.