On the Temperature Sensitivity of Dwell Fatigue of a Near Alpha Titanium Alloy: Role of Strain Hardening and Strain Rate Sensitivity

Excerpt

In the present work, the temperature sensitivity of dwell fatigue of a near alpha titanium alloy IMI 834 is investigated. The time-dependent plastic strain accumulation during dwell fatigue loading is used to assess the temperature sensitivity of dwell fatigue. The plastic strain accumulation was considerably high at room temperature and very low at 360 °C. This decades old phenomenon is given a revitalized perspective in the current study. Phenomenological modeling using the Kocks–Mecking approach is used to obtain microstructure-based explanations for this observed difference in dwell strain accumulation. Using this approach, dwell sensitivity is correlated with the monotonic strain-hardening behavior and strain rate sensitivity for the first time. Insights into the role of solutes in the form of dynamic strain aging (DSA) on dwell fatigue are also thoroughly explained. A simple model considering the combined effects of strain hardening and strain rate sensitivity (SRS) on dwell fatigue is used to predict the dwell fatigue strain evolution at different temperatures. Consequently, a much simpler way of predicting the dwell fatigue response is also demonstrated. Based on these results, some recommendations for developing dwell fatigue-resistant materials are also made. …