(1. 沈阳航空航天大学 机电工程学院，沈阳 110136；
2. 沈阳航空航天大学 航空制造工艺数字化国防重点学科实验室，沈阳 110136)
摘 要: 针对典型高速列车车体用6N01铝合金，对十字角接接头的显微组织和疲劳性能进行研究。结果表明：十字角接接头的焊缝组织为等轴状铸态组织；在热影响区，与淬火区晶粒尺寸相比，过时效区晶粒尺寸增大，同时析出大量Mg2Si相。显微硬度试验结果表明，十字角接接头的焊缝显微硬度最低，平均值为94.2 HV；热影响区的显微硬度平均值为111.6 HV，但在距离热影响区中心0.25 mm左右的区域，显微硬度下降至108.5 HV，形成软化区。室温环境下，获得应力比为0.5和-1的疲劳S-N曲线，与母材相比，十字角接接头的室温疲劳强度分别降低了75.1%和64.4%。应力集中程度较高的焊趾导致疲劳裂纹易于萌生，同时接头处强化相聚集长大，导致焊缝强度降低，合金疲劳极限降低。
关键字: 6N01铝合金；十字角接接头；显微结构；疲劳性能
（1. School of Mechatronics Engineering, Shenyang Aerospace University, Shenyang 110136, China;
2. Key Laboratory of Fundamental Science for National Defense of Aeronautical Digital Manufacturing Process, Shenyang Aerospace University, Shenyang 110136, China）
Abstract:Aiming at a typical 6N01 aluminum alloy used in high-speed train bodies, the microstructure and fatigue performance of the cross angle joints were studied. The results show that the weld zone consists of equiaxed grains which is a typical as-cast structure. In the heat-affected zone, the size of equiaxed grains in the over-aged zone is bigger than that of the quenched zone due to the welding heat. Meanwhile, a large amount of Mg2Si particals can be found inside the heat-affected zone. The lowest microhardness position locates inside the weld zone , with an average value of 94.2 HV. The average microhardness of the heat-affected zone is 111.6 HV, but the value decreases to 108.5 HV in the area about 0.25 mm away from the center of the heat affected zone, forming a softened zone. At room temperature, fatigue S-N curves are obtained. The analysis shows that the fatigue strength of the cross angle joint decreases by 75.1% and 64.4%, respectively, with stress ratios of 0.5 and -1 compared with the base metal. The weld toes with high stress concentration cause fatigue cracks to easily initiate, and at the same time, the aggregating and growing up of the strengthening phase at the joint results in the strength and fatigue limit decrement of the 6N01 aluminum alloy weld.
Key words: 6N01 aluminum alloy; cross angle joint; microstructure; fatigue performance
