7050铝合金FSW接头微区低周疲劳裂纹扩展行为  

Fatigue crack growth behavior of 7050 aluminum alloy friction stir welded joint

作　　者：金玉花[1,2] 张林[1] 张亮亮[1] 王希靖[1] JIN Yuhua;ZHANG Lin;ZHANG Liangliang;WANG Xijing(Lanzhou University of Technology,Lanzhou,730050,China;State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals,Lanzhou University of Technology,Lanzhou,730050,China)

机构地区：[1]兰州理工大学,兰州730050 [2]兰州理工大学,省部共建有色金属先进加工与再利用国家重点实验室,兰州730050

出　　处：《焊接学报》2020年第10期11-16,I0001,I0002,共8页Transactions of The China Welding Institution

基　　金：国家自然科学基金资助项目(51865028);甘肃省高等学校基本科研业务费(01-0071).

摘　　要：对5 mm厚铝合金7050搅拌摩擦焊接头微区进行了低周疲劳裂纹扩展试验,研究了焊核区、前进侧及后退侧热力影响区的疲劳裂纹扩展行为.结果表明,焊核区的疲劳裂纹扩展速率最快,前进侧热力影响区次之,后退侧热力影响区最慢.焊核区疲劳裂纹呈沿晶与穿晶混合方式扩展,热力影响区的裂纹主要以穿晶方式进行扩展.裂纹偏转或裂纹产生分支是热力影响区疲劳裂纹扩展速率降低的原因.疲劳裂纹扩展初期,焊核区断口有疲劳辉纹出现;热力影响区断口并没有找到疲劳辉纹,而是出现了轮胎压痕花样.疲劳裂纹稳态扩展期,焊核区和热力影响区断口均有疲劳辉纹.The fatigue crack growth behavior of 5 mm thick 7050 aluminum alloy friction stir welding joints in different areas was analyzed and studied.The results show that the fatigue crack growth rate is the fastest in the weld nugget zone.The second is the position of the thermo-mechanically affected zone of advancing side.The fatigue crack growth rate is the slowest in the thermo-mechanically affected zone of retreating side.The fatigue crack is propagated by intergranular and transgranular mixing in the weld nugget zone,while the crack is propagated by transgranular in the thermomechanically affected zone.The deflection of the crack and the generation of the crack branch will reduce the fatigue crack growth rate.In the initial stage of fatigue crack growth,the fracture surface of the weld nugget zone is distributed with grain size fracture planes,and fatigue striations are generated;fatigue striations did not occur in the thermo-mechanically affected zone,but tire indentation patterns appear here.During the steady-state propagation of fatigue crack,the crack growth rate increased,and fatigue striations appeared in the weld nugget zone and the thermo-mechanically affected zone,and secondary cracks were generated.

关 键 词：7050铝合金 搅拌摩擦焊 疲劳裂纹扩展速率 疲劳断口 

分 类 号：TG453[金属学及工艺—焊接]