OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 2 2025 Fig. 5. Microhardness distribution in the crosssection of rods after various degrees of CRF 600 HV0.2 and becomes even more pronounced. In this case, the highest overall level of microhardness is observed – 500-600 HV0.2. Fig. 6 and Table 1 show the tensile stress-strain diagrams and mechanical properties of Fe-21Mn-6Al1C steel in the initial state (after preliminary quenching to the austenite structure) and after CRF with different degrees. In the initial state, the steel under study demonstrates pronounced strain hardening, as well as a high level of ductility (elongation to failure (δ) = 56-58 %; uniform elongation (δu) = 48-50 %) and good strength properties (ultimate tensile strength (σu) = 830 MPa; yield strength (σ0.2) = 460 MPa). Tensile testing of the cold-forged Fe-21Mn-6Al-1C steel specimens showed that the material of the center and edge of the rod demonstrates significantly different mechanical behavior (Fig. 6) and, consequently, mechanical properties (Table). Thus, the specimen cut from the center of the rod subjected to 20 % CRF possesses high ductility (δ = 51.4 %; δu = 37.9 %) along with pronounced strain hardening (Fig. 6). At a b c d e Fig. 6. Uniaxial tensile stress-strain curves of Fe-21Mn-6Al-1C steel in the initial state (a) and after CRF with ε = 20% (b), ε = 40% (c), ε = 60% (d), and ε = 80% (e)
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