*3.2. Q&P Experiments, Steel A*

Figure 5 shows examples of the obtained XRD spectra for the quenched and partitioned specimens. There is clearly an appreciable amount of retained austenite following quenching and partitioning. The peaks corresponding to the ferrite phase coincide almost exactly among Steels A, B and C, while a slight scatter in the locations of the austenite peaks can be detected between the Steels. This is an indication that the lattice parameters of austenite in the Steels are affected by carbon partitioned from supersaturated martensite, each Steel having received a different amount of carbon in the austenite phase after quenching to the temperatures indicated in the figure.

**Figure 5.** The observed XRD spectra for Steel A, quenched to 175 ◦C, Steel B, quenched to 300 ◦C and Steel C, quenched to 100 ◦C. All specimens were annealed at 850 ◦C for 4 min and partitioned at 450 ◦C for 100 s.

Figure 6 shows the measured retained austenite fraction and the calculated austenite carbon content with respect to the initial quench temperature for Steel A. As can be seen from the figure, the quench temperature correlates with the amount of retained austenite in the final microstructure. The carbon content of the retained austenite drops as the initial quench temperature is raised.

**Figure 6.** (**a**) The retained austenite fraction of Steel A with respect to initial quench temperature *QT*. (**b**) The carbon content of the retained austenite with respect to *QT*. Specimens annealed at 850 ◦C, quenched to *QT* and partitioned at 450 ◦C for 100 s.

Figure 7 shows the measured 0.5% proof strength (denoted *Rp*<sup>05</sup> in the Figures), ultimate tensile strength *Rm*, uniform elongation *Ag* and the total elongation *A* with respect to the initial quench temperature. Figure 6b shows that *Ag* correlates with the initial quench temperature. There is a slight inverse correlation with the total elongation. It is to be noted that the *Rm* practically stays at about 1000 MP irrespective of the quench temperature.

**Figure 7.** (**a**) The measured 0.5% proof strength and *Rm* values for Steel A with respect to *QT*. (**b**) The uniform elongation *Ag* and total elongation *A* for Steel A with respect to *QT*. Specimens annealed at 850 ◦C, quenched to *QT* and partitioned at 450 ◦C for 100 s.
