T6态7A09铝合金搅拌摩擦焊接接头的疲劳性能及组织

摘要

The 7A09-T6 aluminum alloy was welded by the FSW. The fatigue property of joints prepared by different processes was tested by high frequency fatigue testing machine and the S-N curves were obtained. In addition, the fatigue fracture of welding joints were studied by OM and SEM. The results show that fatigue life was shorter with the increase of the stress amplitude, and the fatigue life of welded joints was the longest when welding speed was 37. 5 mm ? Min-1. The fracture of the joints was located in the juncture of the heat affected zone and the nugget, the obvious plastic deformation was not found in this area. Moreover, the joints fatigue fracture existed at the bottom of the welding sample and the fatigue striations were found in expansion area, the instantaneous break area showed a dimple morphology. All of the above were the typical tear characteristics of static load.%用搅拌摩擦焊工艺对T6态7A09铝合金进行了焊接，用程控高频万能疲劳试验机测试了不同工艺焊接接头的疲劳性能，并得出S-N曲线，用光学显微镜及扫描电镜对焊接接头的疲劳断口进行了研究。结果表明：应力幅值越大，焊接接头的疲劳寿命越短；焊接速度为37.5 mm·min-1时的接头疲劳寿命最高；接头断裂位置在前进边的热力影响区与焊核交界处，未发生明显的塑性变形；接头疲劳断口起裂于接头底部，在扩展区出现疲劳辉纹，瞬断区呈韧窝状，具有典型的静载撕裂特征。