Fig. 1 APT reconstructed 3D distribution map of CRPs delineated by 10 at.% Cu isoconcentration surfaces in the steel samples isothermally aged at 500 °C for a 1 h, b 4 h, c 16 h, d 64 h. The CRPs marked by arrow are selected for further composition analysis

Fig. 2 Size distribution integrated with the average diameter (D p), number density (N v) of the CRPs in the steel samples quenched and aged at 500 °C for a 1 h, b 4 h, c 16 h,d 64 h

Fig. 3 Proxigram concentration profiles for Fe, Cu, Ni, and Mn with respect to 10 at.% Cu isoconcentration surfaces of the selected CRPs marked by arrow in Fig. 1, integrated with the APT reconstructed 3D atom maps, equivalent diameters, Dp, and composition of the separate CRPs. Steel samples aged at 500 °C for a 1 h, b 4 h, c 16 h, d 64 h

Fig. 4 a APT reconstructed 3D atom distribution map of Cu, Ni, Mn, C, Cr, Mo, Si, and Fe atoms in and around a selected CRP with elongated rod-shaped marked green rectangle in Fig. 1d. b Composition profile of the CRP along Z direction (blue line) in a, showing the redistribution behavior of the solute atoms across the precipitate. Sample tempered at 500 °C for 64 h

Fig. 5 Schematic illustration of compositional evolution of CRPs showing the distribution of Cu (red), Fe (gray), Ni (green), and Mn (blue) in the CRPs approaching their equilibrium composition