GH909合金激光焊接接头的微观组织特征  

Microstructural Characteristics of Laser Welded Joints of GH909 Alloy

作　　者：张良[1] 闫飞 Zhang Liang;Yan Fei(School of Mechanical and Electrical Engineering,Suzhou Vocational University,Suzhou,Jiangsu 215104,China;School of Automobile Engineering,Wuhan University of Technology,Wuhan,Hubei 430070,China)

机构地区：[1]苏州市职业大学机电工程学院,江苏苏州215104 [2]武汉理工大学汽车工程学院,湖北武汉430070

出　　处：《中国激光》2022年第8期34-42,共9页Chinese Journal of Lasers

基　　金：湖北省自然科学基金(2019CFB210)。

摘　　要：采用光纤激光器对2mm厚GH909合金进行焊接实验,探究了焊缝横截面宏/微观成形、外延生长组织演变和接头典型位置的晶体分布特征。研究结果表明:GH909合金焊缝呈典型的沙漏形,焊缝区晶粒尺寸明显大于母材和热影响区的晶粒尺寸;典型的柱状晶析出在焊缝中部和下部,少量等轴晶在焊缝顶部形成;平面生长的针状晶优先在上部近焊缝区形成,并通过竞争淘汰转变为稳定生长的细长柱状树枝晶,与此同时,中部近缝区发生胞状晶、胞状树枝晶向柱状树枝晶的转变;迁移晶界出现在热影响区,焊缝中靠近熔合线的位置存在外延生长和非外延生长两种生长模式;焊缝中部晶粒呈现为典型的非连续生长特征,晶粒宽度由小变大,但立即被新晶粒代替;焊缝上部晶粒的生长方向一致,呈现聚集特征,连续生长的γ柱状晶最终形成贯穿的巨大晶粒。Objective Owing to the excellent performance and the low coefficient of thermal expansion at high temperatures,Fe-Co-Ni-based superalloys have been widely used in the precision structural components of aerospace.As these alloys lack a Cr element,there is no volume expansion effect caused due to solid-phase transformation.Meanwhile,the presence of Nb,Ti,and Al makes these alloys prone to element segregation and cracking during solidification.Certain products will be discontinued,and flight safety may be seriously affected.Based on this,laser welding was performed on GH909 alloy to investigate the microstructure evolution and the orientation characteristics of the joints.Many studies have been published on the relationship between the weldability,the microstructure,and the joint properties of 900 series superalloys.However,there have been few studies on the joint evolution of microstructures and crystal orientation properties.As a result,we investigated the macroscopic forming,microstructure,and crystal orientation properties of laser-welded joints made of the GH909 alloy to rich related therory of GH909 superalloy welding metallurgy and expand application field of laser welding.Methods This study conducted experimental investigations on 2 mm thickness GH909 alloy plates.The welded article was transversely sectioned with a line cut machine into three samples for microstructural examination.Samples were fabricated via a series of rough grinding,fine grinding,and mechanical polishing.The electrolyte and aqua regia diluent were used to remove the stress on the surface and display the partition and the microstructural characteristics of the joints using the scanning electron microscopy in backscattered electron mode and electron backscattered diffraction technique.Results and Discussions The weld of GH909 alloy presented a typical“hourglass shape”and the weld-zone grain size was larger than that of the base metal and heat-affected zone(Fig.3).Typical columnar grains precipitated in the middle and the lower parts of

关 键 词：激光技术 激光焊接 GH909合金 微观组织 晶体取向 

分 类 号：TG456.7[金属学及工艺—焊接]