## 3 Results and Discussion
### Mechanical Properties  
Figure 4 presents the engineering stress-strain curves of the Fe-13 Cr-4 Al alloy, which were recorded over a wide temperature range of 200 to 800 \({}^{\circ}\)C at a constant strain rate  
Figure 3: (**a,b**) SEM images of the Fe-13 Cr-4 Al alloy. (**c**) EDS results of area (**b**) showing the distribution of alloy constituent. Figure 2: (**a,b**) Optical images of the Fe-13 Cr-4 Al alloy. of 10\({}^{-3}\) s\({}^{-1}\). In all instances, a distinctive two-stage characteristic is evident, comprising an elastic deformation phase followed by a plastic deformation phase for all specimens. This suggests that the fracture modes of the FeCrAl alloy specimens inherently possess ductile characteristics. The alloy exhibits prominent strain hardening from 200 to 500 \({}^{\circ}\)C, while strain softening dominates over 600 \({}^{\circ}\)C. Strain hardening only occurs briefly on the stress-strain curve, at 600 \({}^{\circ}\)C, before the softening process takes control and continues until fracture, indicating that 600 \({}^{\circ}\)C is a transition point in terms of the dominant deformation mechanisms at work. Notably, serrations emerge on the stress-strain curves only at the intermediate temperatures of 300 and 400 \({}^{\circ}\)C. In addition, the single spike or drop in stress occurs at the early stage of stress-strain curves at 600-800 \({}^{\circ}\)C, caused by the change in the control mode from the straining control to displacement control, and therefore is unrelated to the serration behaviors. Mechanical properties, such as the ultimate tensile strength, yield strength, elongation, and reduction in area, were determined, with temperature dependencies of these mechanical properties shown in Figure 5. The yield strength was determined at a 0.2% offset from the plastic strain on the stress-strain curve, while ductility was evaluated by measuring the total plastic elongation until fracture. Notably, as the temperature increased, the yield strength generally decreased, reaching a plateau between 200 and 300 \({}^{\circ}\)C. However, a rapid reduction in yield strength was observed above 600 \({}^{\circ}\)C, which was attributed to the intensified strain-softening effect. Similarly, the ultimate tensile strength reached a plateau in the range of 200 to 400 \({}^{\circ}\)C, with a peak value at 400 \({}^{\circ}\)C. Above 500 \({}^{\circ}\)C, a significant reduction in ultimate tensile strength was evident due to the enhanced strain-softening effect. The reduction in area decreased as the temperature increased from 200 to 300 \({}^{\circ}\)C and then stayed low until 400 \({}^{\circ}\)C, before increasing rapidly with the temperature. In the 300-400 \({}^{\circ}\)C temperature range, the reduction in area parameter plateaued where serrated flow took place. Elongation also reached a minimum at 300 \({}^{\circ}\)C, with its second lowest at 400 \({}^{\circ}\)C. The statistical results, including the mean values and standard deviations of yield strength, tensile strength, elongation, reduction in area, strain-hardening exponent, and strain intensity coefficient, are presented in Table 1.  
To further quantify the degree of strain-hardening under different deformation conditions, the strain-hardening exponent was obtained from the log plots of the true stress-strain curves of the FeCrAl alloy until necking. The strain-hardening exponent \(n\) was calculated according to the equation [35]  
Figure 4: Typical engineering stress–strain curves of the Fe-13 Cr-4 Al alloy at various temperatures under a constant strain rate of 10\({}^{-3}\) s\({}^{-1}\). \[\sigma_{t}=K\varepsilon_{t}n, \tag{1}\]  
where \(\sigma_{t}\) denotes the true stress, \(\varepsilon_{t}\) denotes the true strain, and \(K\) denotes the strain intensity coefficient.