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

Abstract

The Σ = 2 twist carbide grain boundary with a (100) 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⟨23⟩ 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.

Keywords:

• tungsten carbide
• grain boundary structure
• dislocations

Acknowledgments

Jany, what a great energy and scientific impulsion you gave to the community of people working in the field of grain boundaries and especially during our French meetings “J2im.” We keep in mind your vivacious face and smiling eyes.

We thank P. Bayle from CEA Grenoble for availability of the JEOL 4000EX microscope and Pr. G. Wahnström for fruitful discussion on WC/Co interface energetics. The authors are also grateful to the Sandvik Company to provide them the possibility of developing basic research on cemented carbides.