Micropillar compression of single crystal tungsten carbide, part 2: Lattice rotation axis to identify deformation slip mechanisms

Abstract

The plastic deformation mechanisms of tungsten carbide at room and elevated temperatures influence the wear and fracture properties of WC-Co hardmetal composite materials. The relationship between residual defect structures, including glissile and sessile dislocations and stacking faults, and the slip deformation activity, which produce slip traces, is not clear. Part 1 of this study showed that 101¯0 was the primary slip plane at all measured temperatures and orientations, but secondary slip on the basal plane was activated at 600 °C, which suggests that 〈a〉 dislocations can cross-slip onto the basal plane at 600 °C. In the present work, Part 2, lattice rotation axis analysis of deformed WC micropillar mid-sections has been used to discriminate 〈a〉 prismatic slip from multiple 〈c + a〉 prismatic slip in WC, which has enabled the dislocation types contributing to plastic slip to be distinguished, independently of TEM residual defect analysis. Prismatic-oriented micropillars deformed primarily by multiple 〈c + a〉 prismatic slip at room temperature, but by 〈a〉 prismatic slip at 600 °C. Deformation in the near-basal oriented pillar at 600 °C can be modelled as prismatic slip along 〈c〉 constrained by the indenter face and pillar base. Secondary 〈a〉 basal slip, which was observed near the top of the pillar, was activated to maintain deformation compatibility with the indenter face. The experimentally observed lattice rotations, buckled pillar shape, mechanical data, and slip traces are all consistent with this model.