On the origin of amorphous nanobridge formation behind the crack tip in an fcc-structured high-entropy alloy: A molecular dynamics simulation study

The Cantor high-entropy alloy (HEA) is a concentered solid solution alloy with a face-centered cubic structure. While plastic deformation in Cantor HEA is usually dominated by deformation twinning and dislocation slip, the recent in situ straining transmission electron microscopy studies reported a crystalline to amorphous phase transformation behind crack tips for ultrafine-grained Cantor HEAs. To reveal the origin of the experimentally observed amorphization behind the crack tip, in this study, molecular dynamics (MD) simulations are performed. MD results reveal that the solid-state amorphization originates from the pinning of high density of wavy dislocations which have jerky motions due to the high lattice resistance to dislocation glide. Moreover, calculated Peierls stress using generalized stacking fault energy curve by nudged elastic band method demonstrates that the high lattice distortion in the modeled HEA leads to significant high stresses that can impede the gliding of dislocations. Graphical abstract