摘要
采用静轴肩搅拌摩擦焊技术实现了8.5 mm厚2A14-T4铝合金T形接头的焊接,研究了接头的宏观成型、显微组织及力学性能。结果表明:焊缝表面呈现光滑无弧纹特征,焊缝外部和内部未发现焊接缺陷;SSFSW T形接头截面焊接区域形貌整体呈现两头宽、中间窄的“开口哑铃”状,焊核区晶粒表现为取向随机的等轴晶,焊核区平均晶粒尺寸表现为第二次焊核区最大,焊接重合区次之,第一次焊核区最小。焊核区再结晶机制以几何动态再结晶为主并伴随有部分连续动态再结晶;热机影响区较窄且晶粒被拉长变形,热影响区组织晶粒长大粗化;焊接过程中第二相粒子的析出粗化造成焊核区硬度降低,硬度最低点出现在第一道焊缝热影响区与热机影响区的交界处;接头的硬度较低区域和结构尺寸引起的应力集中导致T形接头底板与筋板容易萌生裂纹、发生断裂;断口中存在较多的撕裂棱以及大小不一的韧窝,在韧窝中存在尺寸不均匀的第二相颗粒,断口呈现韧性断裂特征。
2A14-T4 aluminum alloy T joint with a thickness of 8.5 mm was connected by stationary shoulder friction stir welding(SSFSW).The weld formability,microstructures and mechanical properties of T joint were studied.The results showed that the smooth surface with small flash could be obtained and no defects were found in SSFSW welds.The cross section morphology of SSFSW-T joint presents an“open dumbbell”with both ends wide and middle narrow.Recrystallization occurred and the grain size decreased obviously in the weld nugget zone(WNZ).The average grain size was the largest in the second weld nugget zone(WNZ2),followed by the weld nugget overlap zone(WNOZ)and the smallest grains were in the first weld nugget zone(WNZ1).The recrystallization mechanism in WNZ is mainly geometric dynamic recrystallization(GDRX)and partially continuous dynamic recrystallization(CDRX).The thermo-mechanically affected zone(TMAZ)is narrow and the grains were elongated.And the grain coarsening occurred in heat affected zone(HAZ).During the welding process,the second phase particles were precipitated and coarsened,resulting in the decreasing hardness of WNZ.The fracture locations of T joint bottom plate and reinforcement plate were in the lowest hardness zone located in the borderline between TMAZ and HAZ and stress concentration locations in tensile test,respectively.Tear ridge and deformation dimples of different sizes could be observed in the fracture surface.And the second phase particles appear in the dimples,showing the characteristics of ductile fracture.
作者
杨海峰
赵洪运
许欣欣
孙广达
周利
赵慧慧
刘会杰
YANG Haifeng;ZHAO Hongyun;XU Xinxin;SUN Guangda;ZHOU Li;ZHAO Huihui;LIU Huijie(State Key Laboratory of Advanced Welding and Joining,Harbin Institute of Technology,Harbin 150001,China;Key Laboratory of Special Welding Technology Shandong Province,Harbin Institute of Technology(Weihai),Weihai 264209,China;Shanghai Aerospace Equipments Manufacturer Co.,Ltd.,Shanghai 200245,China)
出处
《材料导报》
EI
CAS
CSCD
北大核心
2021年第20期20045-20051,共7页
Materials Reports
基金
国防基础科研重点项目(JCKY2017203B066)。
