Physical Mesomechanics | 2021
Very High Cycle Fatigue Failure of Near β Titanium\n Alloy
Abstract
Abstract Fracture behavior of VT22 near β titanium alloy produced by radial shear rolling and subsequent aging was studied in very high cycle fatigue tests with ultrasonic vibration frequency. This type of processing was shown to significantly increase the static and fatigue strengths of the alloy. According to fractographic analysis, the transition from very high cycle to high cycle fatigue failure occurs in the stress amplitude range of 850–900 MPa, which is almost two times higher than the fatigue limit of the conventionally produced VT22 titanium alloy. It was found that fatigue crack initiation in the very high cycle fatigue region is associated with the formation of a fracture facet inclined at an angle of less than 90° to the specimen axis. The facet exhibits a higher local concentration of interstitial impurities (carbon and oxygen) compared to the chemical composition of the surrounding material, which is due to diffusion mass transfer from the adjacent regions to the zone of highest compressive-tensile stresses.