Effect of High-Temperature Thermomechanical Treatment on Microstructure and Mechanical Properties of an Austenitic Steel with Dispersed Particles

The features of microstructure and mechanical properties of an austenitic reactor steel with dispersed particles after high-temperature thermomechanical treatment with plastic deformation after heating to T=1100 and 600 degrees C are investigated. It is shown that as a result of processing with heating to T = 1100 degrees C, plastic deformation develops in localized regions of the material and a fragmented microstructure with predominantly low-angle misorientation boundaries is formed. After deformation with heating to T = 600 degrees C, fragmentation develops more intensively with the formation of both low- and high-angle misorientation boundaries. The elemental composition of dispersed carbide particles of the MC type in steel is studied. It is shown that these particles have a complex composition based on Ti, Nb, and Mo. The elemental composition of the matrix after the treatments corresponds to the nominal one, which indicates that a significant proportion of carbide-forming elements remains in the solid solution and does not participate in the formation of dispersed particles. These structural states provide an increase in the yield strength of steel up to approximate to 550-740 MPa compared to the initial values with a relative elongation of approximate to 7-12.5%. It should be noted that the main contribution to strengthening (Delta sigma approximate to 350-540 MPa) is provided by the fragmented structure, while the contribution of dispersed particle hardening is Delta sigma(disp) <= 35 MPa.