## 2 Materials and Methods
### Material Characterization  
After heat treatment, microstructural parameters were measured using multiple material characterization techniques. The experimental procedure is explained in more detail in [21; 43].  
Volume fractions of each phase were measured using a combination of back-scatter-electron (BSE) images, electron backscatter diffraction (EBSD) and X-ray diffraction (XRD). Samples of the produced materials were analyzed using a Scanning Electron Microscope (SEM) FEI* SEM-Quanta FEG 450 equipped with an EBSD detector. Specim surfaces were prepared by the conventional procedure of metallographic sample preparation: grinding, diamond polishing and final polishing with colloidal SiO\({}_{2}\). EBSD measurements were carried out with a step size of 0.05 um in the conventional configuration of 70\({}^{\circ}\) inclined samples. The EBSD measurements were then post processed with the EDAX-OIM AnalysisTM software. The EBSD diffraction pattern sharpness--quantified by the Image Quality (IQ) factor averaged over each grain--was used to distinguish bainite from martensite. The volume fraction of martensite measured by this method in fact refers to two different kinds of martensite, namely martensite-austenite (MA) islands and low-carbon-martensite (LCM), which, similar to bainite, contains carbides. Combining Klemm etchant and back-scatter electron (BSE) images allows distinguishing the MA islands and measuring their volume fraction. The amount of LCM was obtained by subtracting the MA fraction from the total martensite fraction obtained from EBSD. Additionally, the X-ray diffraction technique (Bruker-D8) was used to quantify the fraction of RA according to ASTM E975-13. The \(\{200\}_{\alpha}\), \(\{211\}_{\alpha}\), \(\{200\}_{\gamma}\) and \(\{220\}_{\gamma}\) diffraction peaks were taken into account.  
During heat treatment, the carbon becomes unevenly distributed between the different phases. A significant portion of this carbon is consumed in the formation of carbides in the bainite and LCM phases. The fraction and size of these carbides were measured using a JEOL FEG-SEM and LePera etched samples. The carbon in solid solution in bainite was determined through the lattice parameter according to the Ruhl and [PERSON] equation [44], while the martensite carbon fraction was calculated on the basis of nano-hardness measurements. Other elements were assumed to be homogeneously distributed along the bainite and martensite phases according to the composition given in Table 1.  
The EBSD data were also used to measure the crystallographic texture, grain morphology and dislocation densities. With the OIM software, the data were partitioned into grains with 5\({}^{\circ}\) boundaries, and an equivalent ellipsoid and the average orientation were calculated for each grain. The aspect ratio and orientation of the axes of these ellipsoids were used to describe grain shape in the model. Average grain orientations were used to calculate orientation distribution functions (ODFs) using the harmonic method [45]. ODFs were calculated for the bainite and martensite phases with series order \(L=22\) and applying a Gaussian scatter of 7\({}^{\circ}\). Dislocation densities were measured using the kernel average misorientation (KAM) and averaging for bainite and martensite.