Deformation and Ductility of Low-Carbon Steel with Different Magnitudes of Strain Aging Effect. I. Formation of Band Nucleus and Strain Sources

The mechanical properties and deformation characteristics of steel 08Mn2Nb manifesting different magnitudes of the effect of strain aging after the heat treatments with heating at 250°C (τ = 30 min) and air cooling and heating at 680°C (τ = 30 min) and water cooling are studied. It is shown that despite the significantly different strength and ductility properties of the steel after the two treatment modes, it is deformed in the yield plateau according to the same Luders mechanism. The mechanism involves emergence and growth of nucleating centers and nuclei of localized strain bands, their intersection at the center of the sample and formation of initiating centers. Tracing of the parameters that determine the initiating stress of the sources emitting dislocations of planar series, which form the growing nucleus of the band, has made it possible to explain the influence of various factors on the top and bottom yield points in the region of the yield drop. The conditions of implementation of the band deformation mechanism and its combination with distributed deformation, in which dislocations propagate simultaneously in different slip systems, are analyzed.