PhD Thesis Colloquium: Mr. Sureddy Tejanath Reddy (06/04/26)
Thesis title:
Microstructural Origin Of Dwell Fatigue In α Titanium And Near - α Titanium Alloys.
Faculty advisor(s):
Prof. Satyam Suwas
When?
06th April, 2026 (Monday), 03:30 PM (India Standard Time)
Where
KPA Auditorium, Department of Materials Engineering
Abstract:
Titanium and its alloys owing to their high specific strength, excellent high temperature properties, and favourable fatigue and creep performance form a key class of structural materials used in aerospace applications. At the same time, the dwell fatigue behaviour of these alloys critically limits the service life of rotating aero-engine components, with dwell loading often reducing life by more than an order of magnitude relative to conventional cyclic fatigue. This degradation arises primarily from two coupled effects: progressive plastic strain accumulation and the associated damage, and the early onset of faceted crack nucleation that sharply reduces the component life. The present thesis is aimed at examining the elastic-plastic anisotropy, specially its dependence on crystallographic texture which plays a central role in governing deformation behaviour.
The present study develops a detailed understanding of the role of crystallographic texture towards anisotropic micromechanical response and dwell fatigue in commercially pure (cp) titanium. The study uses, apart from rigorous experimental investigations using electron back-scattered diffraction (EBSD), the crystal plasticity fast Fourier transform (CPFFT). The study establishes EBSD-informed CPFFT as an effective route to correlate texture, heterogeneous stress distribution, and dwell fatigue anisotropy in cp-Ti.
Further the role of macrozone (microtextured region, MTR) on dwell fatigue behaviour of the near‑α titanium alloy IMI 834 is discussed. The samples were extracted from a forged billet from the centre and periphery and were loaded along axial (AD) and transverse (TD) directions. Fractography reveals faceted crack‑initiation regions whose scale matches macrozone dimensions, directly implicating MTRs in dwell crack nucleation. Crystal plasticity FFT simulations was employed to understand the deformation behaviour.
This study further delves into examining three-dimensional microstructure and correlating with dwell fatigue crack initiation in IMI 834 and establishes an integrated 3D characterization simulation framework that links microtexture, 3D grain connectivity and facet crystallography to dwell fatigue crack initiation in near‑α titanium alloys.