Atomic structure of the Σ = 2 twist carbide grain boundary in WC-Co alloys

摘要

The Σ = 2 twist carbide grain boundary with a (10 0) habit plane was investigated by high resolution transmission electron microscopy in a WC-Co alloy. The atomic structure at the boundary was determined by comparing experimental images and simulations. It corresponds to the boundary model with the lowest energy according to atomistic calculations. Periodic monolayer interfacial steps, compensating for the parametric misfit at the boundary were studied. The displacement field around the defects was simulated and corresponds to a dislocation with a mixed character and a Burgers vectors equal to 1/6 2 3 lying in the boundary plane. Another step with a larger height and connected to a stacking fault was analyzed. It likely arises from the interaction of a matrix dislocation with the boundary. The observations suggest that the migration of Σ = 2 grain boundaries can be induced by the glide of the monolayer steps along the grain boundary.