电磁耦合处理对Ti2AlNb合金电子束焊缝疲劳寿命的影响

Effect of Electromagnetic Coupling Treatment on Fatigue Lifetime of Ti 2AlNb Electron Beam Welding Joint

在航空发动机机匣的焊接过程中,焊缝作为薄弱部位,将直接影响整个机匣的疲劳性能及服役寿命。通常采用焊后热处理消除焊接热应力,均匀焊缝组织,提高焊缝性能,但对于疲劳寿命的改善效果不明显。本研究创新性地提出电磁耦合处理技术,对热处理后的Ti2AlNb合金电子束焊缝进行调控,提升焊接接头的疲劳寿命,同时研究了在电磁耦合作用下焊缝区材料组织演变规律。结果表明,焊缝疲劳极限由134.2MPa增至159.4MPa,提升18.8%。经电磁耦合处理后,焊缝区域的残余压应力最高提升128.7%。同时,在不改变材料组织和相成分的情况下,在材料内部生成位错墙与位错纠缠,疲劳裂纹源由表层移至次表层,疲劳裂纹扩展速度降低,使得疲劳性能提升。焦耳热效应、电子风力效应与磁致塑性效应的耦合作用促进了位错运动,同时增强了疲劳裂纹扩展障碍。本研究为提升焊缝疲劳寿命提供了一种新方法,并为电磁耦合处理提升焊缝疲劳性能提供了可行性依据。

During the welding process of the aero-engine magazine,the weld will directly affect the fatigue performance a nd service life of the whole magazine as a weak part.The post-weld heat treatment is normally used to eliminate the welding thermal stress,uniform the structure of weld joint and improve the performance;however the improvement effect on fatigue life is insufficient.This research innovatively proposes the electromagnetic coupling treatment technology to regulate the heat treated Ti2AlNb electron beam welds to improve the fatigue life of welded joints and at the same time investigates the evolution of the material structure in the weld joints after electromagnetic coupling treatment.The results show that the fatigue limit of th e weld joint is increased from 134.2 MPa to 159.4 MPa,an improvement of 18.8%.After the electromagnetic coupling treatment,the residual compressive stress is increased by up to 128.7%.Meanwhile,without changing the material structure and phase composition,dislocation walls and dislocation entanglement are generated within the material without changing the microstruc ture and phase composition,and the fatigue crack source is moved from the surface to the subsurface,thus reducing fatigue crack expansion rate,resulting in the improvement of fatigue performance.The coupling effect of Joule heat effect,electron wind effect and magnetoplastic effect promotes the dislocation movement and enhances the fatigue crack expansion.This study provides a new method to enhance the fatigue life of welds and provides a feasibility basis for electromagnetic coupling treatment to enhanc e the fatigue performance of welds.