Scenario for the formation of fretting obtained TTS in TA6V from detailed microstructural analysis

Fretting is defined as surface degradation caused by small oscillatory movements. Fretting in the gross slip regime produces high local stresses at the surface. This results in wear and subsurface plastic deformation, which can create a nanosized-grained structure known as a Tribologically Transformed Structure (TTS). If the condition of TTS formation in the fretted interface is well documented in the literature, the metallurgical transformation leading to this structure is not well known. This article aims to study this phenomenon thanks to an innovative in-depth texture analysis of the TTS which is carried out using a TEM crystal plane indexing technique. Several TTS from different steps in the TTS formation are studied. Special care is taken in determining their texture, and chemical analysis is carried out. Considering the temperatures involved and the successive structures analyzed, a new model of continuous dynamic recrystallization via the apparition of shear bands is proposed to explain the heterogeneity of TTS and its microstructural characteristics.