Chemical inhomogeneity inhibits grain boundary fracture: A comparative study in CrCoNi medium entropy alloy

Grain boundary (GB) fracture is arguably one of the most important reasons for the catastrophic failure of ductile polycrystalline materials. It is of interest to explore the role of chemical distribution on GB defor-mation and fracture, as GB segregation becomes a key strategy for tailoring GB properties. Here we report that the inhomogeneous chemical distribution effectively inhibits GB fracture in a model CoCrNi medium entropy alloy compared to a so-called 'average-atom' sample. Atomic deformation kinematics combined with electronic behavior analysis reveals that the strong charge redistribution ability in chemical disor-dered CrCoNi GBs enhances shear deformation and thus prevents GB crack formation and propagation. Inspects on the GBs with different chemical components and chemical distributions suggest that not only disordered chemical distribution but also sufficient "harmonic elements" with large electronic flexibility contribute to improving the GB fracture resistance. This study provides new insight into the influence mechanism of GB chemistry on fracture behavior, and yields a systematic strategy and criterion, from the atoms and electrons level, forward in the design of high-performance materials with enhanced GB fracture resistance.(c) 2023 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.