High-resolution electron microscopy characterization of 2H and 9R variant in the ferritic steels containing copper

►The crystal structures of the copper precipitates in aged reactor pressure vessel model steel were studied by high-resolution electron microscopy (HRTEM). ►Besides the 9R structure, there exist also 2H structure and stacking faults within a copper precipitate in aged samples (2000 h at 400 °C). ►The (001) plane of the 2H structure copper phase is perpendicular to the (010) plane. ►The 2H variant has a hexagonal unit cell with lattice parameters a = b = 0.254 nm and c = 0.417 nm and axial ratio c/a = 1.642.