高速列车用高强A7N01铝合金焊接接头的组织与性能  

Microstructure and Performance of A7N01 Al Alloy Welding Joint Used in Automotive High-strength

作　　者：倪维源 杨尚磊[1,2] 贾进[1] 白建颍 丁波[1] 

机构地区：[1]上海工程技术大学材料工程学院,上海201620 [2]上海交通大学上海市激光制造与材料改性重点实验室,上海200240

出　　处：《热加工工艺》2014年第19期22-25,共4页Hot Working Technology

基　　金：国家自然科学基金资助项目(51075256);上海市教育委员会科研创新重点项目(11ZZ177)

摘　　要：通过维氏硬度计、扫描电镜、能谱仪对高速列车用A7N01铝合金MIG焊接接头的显微硬度、微观组织、疲劳断口形貌及组织成分进行试验分析。结果表明,焊接接头热影响区淬火区晶粒细小,晶内有很多细小的强化相;软化区晶粒粗大,晶内细小强化相较少,强化相在晶界处聚集长大。热影响区晶内有很多粗大化合物Al8Fe2Si,这些粗大化合物中杂质元素Fe、Si含量较高,容易导致疲劳裂纹的萌生。在粗大化合物的边界部位有强化相MgZn2析出。焊接接头硬度分布不均匀,软化区硬度明显低于淬火区,焊缝硬度最低,为72.1 HV,母材硬度最高,为135 HV。疲劳模拟试验表明,在靠近熔合线的热影响区产生了疲劳裂纹,并在淬火区扩展至试样最终断裂。疲劳裂纹倾向于沿晶扩展,疲劳断口上有很多沿晶二次裂纹。The microhardness, microstructure, fatigue fracture morphology and the microstructure element of A7N01 aluminum alloy MIG welding joints used in automotive high-strength was observed by microhardness testers, SEM, EDS. The results show that the grain size in softened zone is much larger than in quenched zone. While small strengthening phase in grain of softened zone is obvious less than that of quenched zone. Strengthening phase in grain boundary grows up in softened zone. There are many coarse compounds Al8Fe2 Si in HAZ. The coarse compounds are rich in Fe and Si. Thus, they are easy to cause the initiation of fatigue crack. Strengthening phases MgZn2 are observed to be precipitated around the coarse compounds. The microhardness of the welding joint distributes uneven, the highest is in BM which is 135 HV and the lowest is in WZ which is 72.1HV. Through fatigue simulation test, the fatigue fracture generates in the HAZ near FZ. Then, the crack propagates in quenched zone until the final rupture of the sample, and the crack tends to propagate in grain boundary. There are many secondary intergranular cracks in the fracture.

关 键 词：A7N01铝合金 焊接接头 微观组织 显微硬度 疲劳性能 

分 类 号：TG146.2[一般工业技术—材料科学与工程] TG407[金属学及工艺—金属材料]