Chemical decomposition along dislocations during plastic deformation

Chemical decomposition of compound phases has been observed in many engineering alloys subjected to plastic deformation. However, little is known about the role of dislocations moving within compounds in their deformation-induced chemical decomposition. We report observations of chemical decomposition of compound crystals along dislocations with atomic resolution, which is inconsistent with the well-established dislocation theory. Transition-metal (TM) and rare-earth element (RE) atoms in the wake of moving partial dislocations are removed out of Mg-TM-RE compounds in magnesium alloys, producing magnesium nanoslices inside. Glide of partial dislocations forces local transformation from face-centered cubic to hexagonal structures with supersaturated TM and RE in Mg-TM-RE compounds. TM and RE atoms behind moving partial dislocations are then relocated into adjacent magnesium grains through pipe diffusion, under the driving force of supersaturated chemical potential. Our observations demonstrate atomically spatial coupling of individual moving dislocations and chemical decomposition within bulk crystals during plastic deformation, providing insights into dislocations and their roles in materials.