Fig. 1 a Complete production process for IF steels in two distinct routes, b heat treatment schedule for simulated annealing in dilatometer

Fig. 2 Pre-annealed microstructures of a the Normal-IF and b the RE-IF steel, c, d correspond to pole figures of these two microstructures, respectively

Fig. 3 Microstructures of a the Normal-IF steel and b the RE-IF steel samples from a1, b1 cold-rolled states to various interrupted annealed states of different holding times: a2, b2 0 s; a3, b3 3 s; a4, b4 10 s; a5, b5 50 s; a6, b6 80 s; a7, b7 90 s; a8, b8 210 s and a9, b9 690 s, wherein the microstructure evolution is divided into two major stages separated by the critical holding time of around 20 s encountering the recrystallization fraction of more than 96%

Fig. 4 Statistics of microstructural fraction and grain size of the investigated steels during static recrystallization: a area percentage of microstructure groups at the nucleation stage, b average grain size of top five largest grains at the nucleation stage, c average grain size of fully recrystallized IF steel samples during grain growth and coarsening stage

Fig. 5 φ2 = 45° ODF sections of a the cold-rolled Normal-IF steel, b the cold-rolled RE-IF steel, c the fully recrystallized Normal-IF steel, d the fully recrystallized RE-IF steel and their corresponding standard φ2 = 45° section with typical orientation fibres and textures of cubic system

Fig. 6 a Volume fraction Δg, b orientation distribution density f(g) of typical textures in the Normal-IF steel and the RE-IF steel, in which the volume fraction is calculated with the tolerance of 15°

Fig. 7 GNDs density of experimental steels at a cold-rolled state and annealed states with different holding times: b 0 s, c 3 s, d 7 s and e 10 s, wherein the local enlarged drawings a1, b1 and e1 correspond to selected areas in a, b and e, respectively

Fig. 8 a, b Simulated ODFs calculated by the VPSC model, c, d experimental ODFs restructured from the EBSD maps of a, c Normal-IF steel and b, d RE-IF steel

Fig. 9 Calculated a relative activities of {110}6<111>2, {112}12<111>1 and {123}24<111>1 slip systems in IF steels undergoing rolling deformation, and the b schematic diagram of orientation relationships among {112}, {110} and {111} slip planes, as well as c thermodynamic calculation of interaction behaviour among steelmaking elements for IF steels before and after RE addition

Fig. 10 GNDs statistics within typical textures of investigated IF steels from a cold-rolled states to annealed states with holding times of b 0 s and c 3 s, respectively, in which the selected area marked with dashed rectangle is locally enlarged in picture d

Fig. 11 Local enlargements of selected areas A-B from Fig. 3a2, b2 and oriented nucleation behaviours of a the Normal-IF steel and b the RE-IF steel, c simultaneous nucleation morphology of the Normal-IF steel but in RD-TD plane. These special regions marked as Ai=1,2,3,4, Bi=1,2,3, and Ci=1,2,3 were traced to typical crystallographic orientations of {111}<uvw>/{554}<225>, {001}<110> and {112}<110> respectively, in which the rod-like subgrains in Ai=4 originated from shear bands composed of several microbands illustrated in d

Fig. 12 Misorientation variation of the shear bands within γ-fibre textures: (L1) shear bands in RD-TD plane of the Normal-IF steel; (L2) shear bands in RD-TD plane of the RE-IF steel, where the selected shear bands were marked by yellow arrows in Fig. 11a, b

Fig. 13 Different nucleation paths of γ-fibre orientation grains from deformed Fe-matrix: a RD-TD midplane, b RD-ND plane of the Normal-IF steel with 7 s holding time

Fig. 14 a, b Volume fraction of γ-fibre orientations within coarse grains, c, d number fraction of grain boundaries within γ-fibre grains, e, f morphology of orientation clusters in a, c, e the Normal-IF steel and b, d, f the RE-IF steel