Atomic-scale deformation mechanism of nano Cu precipitate along the rolling process of ferritic steel

The deformation behavior of nanoscale precipitates and their interaction with the matrix in the alloys have been rarely explored. In this study, the deformation mechanism of nanoscale soft Cu precipitates and its interaction with ferritic matrix during rolling deformation were studied at the atomic scale. The ellipsoidal Cu precipitates with an average diameter of about 34 nm are flattened into slender rods under rolling reduction of about 70% and are elongated along the rolling direction. The initial K-S orientation relationship was transformed into N-W orientation relationship after rolling deformation. The shear deformations are induced in Cu precipitate near the interface and the serrated boundary are formed combined with the plastic flow of the matrix. A successive lattice torsion band with a width of 1.5 similar to 10 nm was formed at the serrated interface, while there is only local lattice distortion at the smooth interface. The Cu precipitates maintained good deformability and excellent strain coordination ability under severe deformations. These results have important value for understanding the deformation mechanism of Cu precipitates.