Slip Behavior at Grain Boundaries Assessed with Nanoindentation Hardness TaNbTiV Refractory High Entropy Alloy

Preparation of refractory high entropy alloys by melt solidification led to dendritic segregation, which provides different compositions that can be used to assess the mechanical properties as a function of composition using nanoindentation arrays. EBSD orientation maps combined with backscattered electron images show that each grain consists of its own dendrite, and grain boundaries are usually along inter-dendritic zones. Hardness values track with local composition, with softer values in Ta dendrite cores and harder values in the interdendritic regions, but hardness also depended on grain orientation and grain boundaries. Relatively few indents exhibited obvious shear bands, which were usually correlated with {112} slip planes, and more often observed in the softer high-Ta dendrite cores. AFM characterization of selected indents on grain boundaries suggests uniform deformation on both sides of the boundary such that quantifying effects related to slip transfer is difficult.