Slip-stimulated grain boundary sliding in Ti-6Al-4 V at room temperature

Abstract

Grain boundary sliding has a substantial contribution to high temperature deformation of α/β titanium alloys. Despite the low homologous temperature, the operation of grain boundary sliding is presently reported at room temperature using a pre-deformed Ti-6Al-4 V specimen. Scanning electron microscopy and atomic force microscopy observations were combined with electron back-scattered diffraction characterization in order to clarify the underlying mechanisms. Intragranular prismatic slip seemingly triggers grain boundary sliding. The analysis of activated slip systems while accounting for crystallographic aspects unveiled several highly influential parameters. Notably, strain partitioning, as a result of plastic anisotropy and microstructural heterogeneities, promotes grain boundary sliding. The orientation of the incident slip band relative to the boundary plane was also found correlated with the occurrence of grain boundary sliding. These findings lay the foundations for identification of conditions favoring grain boundary sliding in titanium alloys and highlight an enriched panel of possible interactions between slip bands and grain boundaries that is likely to play a critical role in crack initiation processes.