TC17合金电子束焊接接头高周疲劳失效行为研究

电子束焊接构件广泛应用于航空发动机关键部位,其需要满足长寿命与高可靠性的设计要求.针对TC17合金电子束焊接接头,采用旋转弯曲疲劳试验方法,获得焊接接头的高周疲劳性能,同时利用电子扫描电镜对疲劳断口进行微观观察,探明焊接接头的高周疲劳裂纹萌生和扩展机理.结果表明,TC17合金电子束焊接接头在10~7周次的疲劳强度为450 MPa,约为母材强度的81%,试样失效位置均位于焊缝区;试样表面最大应力与内部气孔缺陷处应力集中形成竞争机制,在10~5~10~7周次内,裂纹萌生于内部气孔,在10~7周次后,裂纹萌生于试件表面;试样断口显示出明显的穿晶断裂区和沿晶断裂区,疲劳寿命随沿晶断裂区的应力强度因子下降而增加;气孔面积及真实应力为影响疲劳寿命的主要因素,气孔处应力强度因子与疲劳寿命呈线性下降关系.

Study on High Cycle Fatigue Failure Behavior of TC17 Titanium Alloy Electron Beam Welded Joint

Electron beam welding(EBW)components are widely used in key parts of aeroengine,which need to attain the design requirements of long lifespan and high reliability.In this paper,high-cycle fatigue property of TC17 alloy EBW joint was obtained by rotate bending fatigue test method,and fatigue crack initiation and propagation mechanisms were explored on fracture surface by scanning electron microscope(SEM).The results showed the fatigue strength of TC17 EBW joint at 107 cycles was 450 MPa,which was about 81%of the base metal.Fatigue failure all occurred at the welded zone.The competition between the maximum stress on surface and the stress concentration at internal pore defect resulted in cracks initiated at internal pore within 105-107 cycles and at surface over 107 cycles.Fracture surface showed obvious transgranular and intergranular fracture zones,and the fatigue life increased with the decrease of the stress intensity factor at the intergranular fracture zone.The fatigue lifespan was mainly affected by both the area and the real stress of the pore.The stress intensity factor at the pore and the fatigue lifespan showed a linear descent relationship.