## 4 Discussion  
In this work, the Fe-Mn-5 Si alloy, with chemical composition close to the alloys of the Fe-Mn-Si system, was studied. This system has a useful set of properties: an increased rate of degradation [13], high mechanical characteristics [6] and the maximum shape memory effect, which is ensured by the optimal content of \(\sim\)5% Si and \(\sim\)30% Mn in the composition of the alloy [47]. It is also important to note that the temperature of the martensitic transformation is close to the temperature of the human body [18]. In this work, we planned to use severe plastic deformation by the method of equal-channel angular pressing in order to increase the strength characteristics and the corrosion rate of this alloy [48; 49]. In addition, strengthening and refinement of the structure could increase the shape memory effect of the alloy [50; 51; 52]. To obtain the initial coarse-grained state of Fe-Mn-5 Si, the alloy was annealed for 12 h at a temperature of 1100 \({}^{\circ}\)C. During long-term annealing, a coarse-grained structure with a large number of annealing-twins was formed (Figure 1). The high density of twin boundaries in the Fe-Mn-5 Si alloy and the absence of \(\varepsilon\)-martensite apparently led to a corrosion rate much lower than 0.8 mm/year, obtained in [13] for the Fe-30 Mn-5 Si alloy annealed at a temperature of 900 \({}^{\circ}\)C in an hour. After ECAP, the austenitic state of the Fe-Mn-5 Si alloy was retained due to the deformation temperature of 400 \({}^{\circ}\)C, which is much higher than the range of possible martensitic transformation. The austenitic state of Fe-based alloys for medical use is the most acceptable because of the possibility to use MRI as a control for the implantable device. It should be noted that 5.12% Si decreases significantly stacking fault energy (SFE) of the alloy, since twinning in Fe-Mn alloys with a similar Mn content is not typical for high-temperature deformation [42; 43]. However, the fact that twinning played a decisive role in the formation of the structure during deformation (Figure 4) resulted in the fact that the corrosion rate remained practically unchanged. The high density of defects in the crystal structure (Table 1) was compensated by an increase in corrosion resistance due to low energy boundaries in the fcc iron-based alloy. Apparently, the resulting structural state affected the decreasing of the Young's modulus. In our work, by dynamic indentation, we obtained a decrease in [PERSON]'s modulus by a factor of 2.6 from 173.3 GPa to 65.9 \(\pm\) 2 GPa (Figure 3b, Table 3). This result is important in the development of alloys for bioresorbable implants, since an important factor for the use of the material is the biomechanical compatibility of the implant and bone. According to the results of the study of hemolytic and cytotoxic activity in vitro, as well as local and systemic reactions of laboratory animals to implants, the Fe-Mn-5 Si alloy after ECAP is deemed biocompatible. Good biocompatibility, high strength and low modulus of elasticity open up excellent prospects for using the alloy in the resulting structural phase state as a material for implantable orthopedic constructions capable of providing stable osteosynthesis during the period of bone defect repair. It is worth mentioning that, due to the high strength characteristics of the Fe-Mn-5 Si alloy after ECAP, it can be used to obtain miniature implants that are nevertheless capable of effectively providing the fastening function during osteoreconstructive surgery (Figure 3a, Table 2). The high specific strength of the alloy obtained by ECAP makes it possible to vary the dimensions of the implant over a wide range. This, in turn, provides additional opportunities to control the degradation time of the implant. It should be noted that ECAP has established itself as an effective tool for structural and phase regulation. Encouraging results have been obtained that require further research.