【摘要】 研究了TC4钛合金薄板激光焊接接头及母材的疲劳性能,并对其疲劳断口进行了观察.结果表明,接头的疲劳寿命在低应力水平时高于母材,在高应力水平时低于母材.母材疲劳裂纹萌生于试样表面;在裂纹扩展区有平行排列的弯曲的二次裂纹和期间更细的疲劳辉纹,瞬断区为细小的等轴韧窝.焊缝疲劳裂纹起源于表面的气孔,源区有笔直且平行排列的二次裂纹;在裂纹扩展区,断口形貌与组织有关,细晶区为韧窝,在细晶与柱状晶交界处为敞口浅韧窝,柱状晶和粗晶区为晶粒大小的刻面,上有大量的微剪切滑移带,断裂机理为滑移带形成及开裂.更多还原

【Abstract】 The fatigue property and fracture mechanism of TC4 titanium alloy joint during laser welding was investigated.It was found that the fatigue life of laser weld was longer than that of the base metal under low stress levels.However,the fatigue life of laser weld was shorter than that of the base metal under high stress levels.Fatigue cracks originated in the surface for base metal specimen.In the fatigue crack expansion zone,numerous curving secondary cracks and fatigue striations were found perpendicular to the direction of crack propagation.Fissures at the root of some fatigue striations were also observed.The fatigue cracks of the weld originated in the pores in the weld surface,and numerous secondary cracks were straight and parallel near the fatigue resource.In the fatigue crack propagation area of the weld,small dimples were found in fine-grain zone and became shallow near the columnar crystal.Mass of micro-shear sliding bands and shallow dimples were found in the weld center.The fracture mechanism of the weld was formation of shear sliding bands and rupture.更多还原