## 3 Results and Discussion
### Identification of Serrations
Serrations diminished as the temperature increased further, resulting in smooth stress-strain curves, as shown in Figure 4. Based on a comprehensive analysis of the evolution of serration types with deformation temperature, along with changes in strength, ductility, and strain-hardening exponent across different temperatures, it is evident that the serration temperature range for the current Fe-13 Cr-4 Al alloy lies between 300 and 400 \({}^{\circ}\)C. The interaction between mobile dislocations and diffused solute atoms gives rise to serrations, which in turn leads to a rise in the flow stress and postpones the reduction in stress with an increase in deformation temperature. Consequently, within this temperature range (300 to 400 \({}^{\circ}\)C), notable plateaus in yield strength and ultimate tensile strength were observed. Additionally, the peak values of both the strain-hardening exponent and the strain intensity coefficient were also recorded within this temperature interval. Although DSA enhances the flow stress of the material, it concurrently reduces its ductility, as demonstrated by the minima observed in ductility parameters in Figure 5, such as the elongation and reduction in area. Prior studies [29,30] have documented comparable characteristics in FeCrAl alloys, specifically the DSA-induced plateaus and peaks in yield strength and ultimate tensile  
Figure 10: Representative engineering stress–strain curves under four deformation conditions showing different serration types: (**a**) 300 \({}^{\circ}\)C and (**b**) 400 \({}^{\circ}\)C.  
strength as a function of temperature. Given that the reduced ductility of the FeCrAl alloy constrains its formability, the DSA phenomenon warrants serious consideration and should be avoided. Furthermore, recent research has also highlighted that the cyclic hardening attributed to the DSA effect adversely impacts the low-cycle fatigue life of steels, which poses a significant concern for their structural applications [39, 40]. Consequently, there is a pressing need to conduct a comprehensive investigation into the effects of DSA on the mechanical properties of FeCrAl alloys. To further investigate the influence of deformation temperature on serration behavior, a statistical analysis of the stress drop magnitude was conducted. The magnitude of the stress decrease (\(\Delta\sigma\)) represents the difference between the maximum and minimum stresses within each serration, as shown in Figure 10. Previous studies have demonstrated that the statistical analysis of stress drop magnitudes is a valuable tool for comprehending the serrated flow phenomenon [25, 41, 42, 43]. Figure 11 shows the distribution of stress drop magnitudes at temperatures of 300 and 400 \({}^{\circ}\)C. To ensure the precision of the statistical results and mitigate any potential deviations due to testing system noise, a threshold value of 0.5 MPa was established for calculating the magnitude of stress drops. As depicted in Figure 11a, the distribution of stress drop magnitudes at 300 \({}^{\circ}\)C exhibited two distinct peaks. One peak corresponded to small stress drop magnitudes, indicative of type-B serrations, while the other peak corresponded to high stress drop magnitudes, associated with type-A serrations. This suggests the coexistence of power law and peak-shaped distributions. When the temperature was increased to 400 \({}^{\circ}\)C, a similar two-peak distribution pattern was observed. One peak, representing small stress drop magnitudes, continued to correspond to type-B serrations, while the other peak, at high stress drop magnitudes, was associated with type-C serrations.