表层组织状态对6005A铝合金MIG焊接头液化裂纹及疲劳性能的影响  

Effects of surface layer microstructure on liquation crack and fatigue properties of 6005A aluminum alloy MIG joints

作　　者：韩晓辉 李帅贞 吴来军 檀财旺[2,3] 李刚卿 宋晓国 HAN Xiaohui;LI Shuaizhen;WU Laijun;TAN Caiwang;LI Gangqing;SONG Xiaoguo(CRCC Qingdao Sifang Co.,Ltd.,Qingdao,266111,China;State Key Laboratory of Advanced Welding and Joining,Harbin,150001,China;Shandong Provincial Key Laboratory of Special Welding Technology,Harbin Institute of Technology at Weihai,Weihai,264209,China)

机构地区：[1]中车青岛四方机车车辆股份有限公司,青岛266111 [2]哈尔滨工业大学,先进焊接与连接国家重点实验室,哈尔滨150001 [3]哈尔滨工业大学(威海),山东省特种焊接技术重点实验室,威海264209

出　　处：《焊接学报》2022年第5期14-20,I0004,共8页Transactions of The China Welding Institution

基　　金：国家自然科学基金资助项目(52074097,52005132);山东省重点研发计划(重大科技创新工程)(2021ZLGX01).

摘　　要：采用扫描电镜、透射电镜、电子背散射衍射和高周疲劳试验,研究了表层组织状态对轨道交通用6005A铝合金MIG焊接头液化裂纹及疲劳性能的影响.结果表明,粗晶组织晶界附近第二相粗大,导致热影响区晶界液膜厚度达到8~10μm,使得液化晶界抵抗拉应力的能力降低,从而对液化裂纹缺陷更敏感.因表层粗晶组织形成的液化裂纹成为疲劳过程中可能的裂纹源,对接头疲劳性能产生不利影响.改善母材表层粗晶组织可以抑制液化裂纹的形成,提高接头疲劳性能.在1×10^(7)循环周次下,表层粗晶接头疲劳强度为93 MPa,表层细晶接头疲劳强度为107 MPa.The effects of surface microstructure on liquation cracks and fatigue properties of 6005A aluminum alloy MIG joints used in high-speed train bodies were comparatively studied. The results showed that the second phase near the grain boundary of the coarse-grained microstructure was coarse, resulting in larger thickness of the grain boundary liquid film in the heat-affected zone reaching 8~10 μm, which made the liquefied grain boundary less resistant to tensile stress and more sensitive to liquation cracks. The liquation cracks formed by the surface coarse-grained microstructure become possible crack sources during the fatigue process, which adversely affect the fatigue properties of the joints. Improving the surface microstructure of the base metal could suppress the formation of liquation cracks and improve the fatigue performance of the joint. The fatigue strength of the surface coarse-grained joint was 93 MPa under 1 ×10^(7) cycles, while that of the surface finegrained joint was 107 MPa.

关 键 词：6005A铝合金 粗晶组织 MIG焊接头 液化裂纹 疲劳性能 

分 类 号：TG444.7[金属学及工艺—焊接]