Effects of strain waveform on low cycle fatigue behaviour of near α Timetal 834 titanium alloy

The low cycle fatigue (LCF) behaviour of a near alpha Timetal 834 titanium alloy has been studied under fast-slow and slow-fast waveforms at peak dynamic strain aging (DSA) temperature (450 degrees C). The alloy exhibits inferior fatigue life under slow-fast waveform as compared to fast-slow waveform. This is attributed to slow rate of straining in tensile direction under slow-fast waveform which allows more interaction between mobile dislocations with solute atoms thereby enhancing the strength of DSA. A life prediction model based on the dynamic viscosity with waiting time correction as per dislocation kinetics predicts fatigue lives reasonably well under pronounced DSA effect. (C) 2010 Elsevier Ltd. All rights reserved.