Grain growth and dislocation density evolution in a nanocrystalline Ni–Fe alloy induced by high-pressure torsion

The structural evolution of a nanocrystalline Ni–Fe alloy induced by high-pressure torsion (HPT) was investigated. HPT-induced grain growth occurred via grain rotation and coalescence, forming three-dimensional small-angle sub-grain boundaries. Further deformation eliminates the sub-grain boundaries from which dislocations glide away on different {1 1 1} planes. A significant number of these dislocations come together to form Lomer–Cottrell locks that effectively increase the dislocation storage capacity of the nanocrystalline material. These observations may help with developing strong and ductile nanocrystalline materials.