Влияние исходного состояния низкоуглеродистых сталей на структуру и механические свойства, формируемые при равноканальном угловом прессовании

Fe-Mn-V-Ti-C and Fe-Mo-Nb-V-C subjected to severe plastic deformation by equal-channel angular pressing from various initial states (after normalization, quenching, quenching and the subsequent tempering) were studied using the methods of optical metallography, transmission electron microscopy and X-ray diffraction analysis. The ultrafine-grained structures with the average size of structural elements about 300 nm (ferrite) stabilized by disperse particles were formed under equal-channel angular pressing independently on the initial structural and phase states of steels. The investigated states with the close size of structural elements after equal-channel angular pressing are characterized by various levels of strength properties: the structure formed from initial quenched state possesses the greatest values of 0,2 pct offset yield strength and microhardness (σ 0,2=1125 MPa, H μ=3,7 GPa) in comparison with two other states (σ 0,2 =960-990 MPa, H μ =3,1-3,3 GPa). The authors have analyzed the major physical factors defining a character of ultrafine-grained structure of low-carbon steels after severe plastic deformation and have estimated the contribution of the main hardening mechanisms into steel yield strength. Key words: Low-carbon steel, equal-channel angular pressing, ferrite, pearlite, martensite, particle strengthening, ultrafine-grained structure, «stress-strain» curves, microhardness.