Online Lecture by prof. Satyam Suwas

Understanding microstructural dependence of dwell fatigue in titanium alloys

Speaker: prof. Satyam Suwas, Department of Materials Engineering, Indian Institute of Science, Bangalore, India.

Title:
Understanding microstructural dependence of dwell fatigue in titanium alloys.

Abstract:
The failure of the fan blades of the Rolls Royce gas turbine engine that powered the Lockheed Martin tristar aircraft in 1972, has drawn considerable attention on ambient temperature dwell fatigue (DF) in titanium alloys.

Now, it is well known that titanium alloys (α, near- α, and a few α+β alloys) are sensitive to a dwell period at the peak load of an otherwise normal fatigue loading cycle.
Many industrially relevant α and near α Ti alloys are susceptible to this rather unusual phenomenon. The phenomenon is very interesting in the sense that it is most pronounced at ambient temperature (~25 °C) and vanishes above 200 °C.

Recent investigations have led to an understanding that the phenomenon is strongly dependent on micro-texture. Moreover, the phenomenon is highly anisotropic.

EBSD based investigations have led to the understanding that the difference in texture along different directions leads to the deformation heterogeneities during the deformation.
These heterogeneities could be a possible cause for the anisotropy of dwell fatigue behaviour of titanium alloys along axial and transverse directions.

In this colloquium, a comprehensive understanding of the effect of microstructure and texture on the dwell fatigue of α and near-α titanium alloys will be presented.
The role of strain hardening and strain rate sensitivity of the material on dwell fatigue as well as the role of texture on the anisotropy of dwell fatigue response will be elucidated.

This session was chaired by prof. Leo Kestens (Ghent University).