Quantitative characterization of microtextured regions in Ti6242 billets and its impact on dwell fatigue performance

Abstract

Quantitative characterization of microtextured regions (MTRs) in Ti6242 billets and understanding their correlation with thermal processing are crucial for predicting dwell fatigue performance in aeroengine components. Three industrial-grade Ti6242 billets with 2, 5 and 8 α/β processing cycles were prepared. MTR characteristics—content, size, morphology, and orientation—were analyzed across radial locations (center, mid-radius, edge) using a novel MTR segmentation technique. Results show MTRs diminish with increased α/β processing cycle. In the billet with 2 cycles, MTR content decreases from center to edge, with average MTR size increasing gradually and maximum size rising sharply due to a few large MTRs at the edge. Variations in MTR characteristics across radial locations are linked to differing strain paths and levels. As the α/β processing cycles increase, MTR elimination at the edge relies on maximum cumulative effective strain, while at the center it relies on combined strain path effects of upsetting and cogging processes. MTRs at the mid-radius are the most difficult to eliminate. Low-cycle fatigue life is comparable among billets, but dwell fatigue is significantly poorer in the billet with 2 cycles, where the MTR morphologies are observed in the crack propagation region with sizes comparable to the average MTR size.