Influence of Heat Treatment on Fatigue Resistance of Electron Beam Welded Dissimilar Titanium Alloy Joints

Abstract

The purpose of this study was to evaluate the influence of heat treatment on the microstructural change and low cycle fatigue (LCF) resistance of an electron beam welded (EBWed) dissimilar joint between Ti-6Al-4V and Ti17 alloys. The aging with solution (STA) had a more significant effect on the microstructure and hardness than aging, compared to the as-welded joint. The post-welded joints in both aging and STA conditions were basically cyclic stable at low strain amplitudes up to 0.6%, while cyclic softening occurred at higher strain amplitudes. The fatigue life in the aging condition was slightly longer than that in the STA condition at the lower strain amplitudes. Fatigue crack initiation occurred from the specimen surface or near-surface defect, and fatigue crack propagation was characterized mainly by the fatigue striations coupled with secondary cracks in both aging and STA conditions.

Effect of Microstructure Transformations on Fatigue Properties of Laser Beam Welded Ti‐6Al‐4V Butt Joints Subjected to Postweld Heat Treatment

“…The hardening efect observed in the FZ after SRA1 annealing can be atributed to tempering of the martensitic structure. This efect at relatively low temperatures has already been observed by a number of researchers [6,30,31]. Because metastable ' martensite is supersaturated in stabilizers owing to the difusionless transformation → ', upon annealing, it decomposes into + by precipitation of incoherent particles at dislocations or phase layers at plate boundaries [28].…”