Shear deformation determined by short-range configuration of atoms in topologically close-packed crystal

Abstract Dislocation behaviors, which determine mechanical properties of materials, are generally believed to be controlled by long-range lattice translational order. For intermetallic compounds, however, their structures are often closely related to atomic environments, with the short-range configurations possibly deviating from the long-range translational order. Thus, how dislocations move in these crystals is obscure. Here, we resolve the shear deformation, dominated by atomic-environment polyhedra, in a representative topologically close-packed phase with (Cr,Ni,Al)2Nb stoichiometry, using aberration-corrected scanning transmission electron microscopy combining with atomic-resolution energy dispersive X-ray spectroscopy. Dislocations there have Burgers vectors deviating from slip planes and surprisingly move by switching between two different slip planes. Long-range diffusion and local composition variation assist the dislocation motion, as demonstrated by high temperature quasi-static and room temperature impact deformations. These discoveries demonstrate the defining role of short-range configuration in the deformation of complex structured intermetallics and shed light on the novel behavior of dislocations.