Direct Observation of Matrix‐to‐Precipitate Elemental Diffusion in Severe Plastic Deformation

ABSTRACT Elemental redistribution, particularly the solute exchange between the matrix and precipitates, is a central issue in alloys subjected to severe plastic deformation (SPD). To elucidate this behavior, a nickel–aluminum bronze (NAB) alloy was processed by high‐pressure torsion (HPT), and its microstructural evolution was systematically investigated using multiscale characterization techniques. A dynamic competition between precipitate dissolution and reprecipitation was identified during SPD. More notably, direct evidence was provided for the diffusion of the matrix element Cu into κ precipitates under heavy deformation, leading to the formation of high‐density Cu‐rich AlCu 3 nanoparticles embedded within the κ precipitate. This unusual elemental redistribution was shown to be thermodynamically favorable under the nonequilibrium conditions induced by SPD. By extending a classical size concentration model based on Fick's second law to a multicomponent alloy system, the coupled growth behavior of AlCu 3 nanoparticles and the κ precipitate is successfully rationalized. These results provide new insight into elemental diffusion pathways and microstructural evolution in complex alloys subjected to SPD.