The mechanistic link between macrozones and dwell fatigue in titanium alloys

This paper addresses the role of macrozone crystallography and morphology in dwell fatigue in titanium alloy Ti-6Al-4V. Until now, the relationship between macrozones and dwell fatigue damage has remained mechanistically uncertain, but this paper establishes a mechanistic link between macrozones and dwell fatigue damage, and explains the preference for dwell facets to be sub-surface. It also outlines the criteria which are important in a potential definition of a macrozone (or microtextured region). High aspect ratio (>similar to 4) macrozones are particularly damaging when their long-axes are orientated near-normal to the principal loading direction, such that their basal planes are oriented to within similar to 15 degrees to the principal stress direction. These criteria may be useful in guiding the development of a diagnostic experimental measurement tool (based on EBSD or ultrasonics for example) for macrozone detection in components.

Automated summary

This study establishes a mechanistic link between macrozones and dwell fatigue damage, and outlines important criteria for the definition of macrozones in titanium alloy Ti-6Al-4V.