Microstructure and Mechanical Properties of Austenitic Steel EK-164 After Thermomechanical Treatments

Abstract

The influence of thermomechanical treatments, including low-temperature and subsequent warm deformation, on the microstructure and mechanical properties of an austenitic reactor steel (Russian Grade EK-164) is investigated. It is shown that low-temperature plastic deformation (after cooling in liquid nitrogen) gives rise to the formation of a high density of microtwins. In the course of subsequent warm deformation (at T = 600 or 700° C) the localized deformation bands, having an internal fragmented nano-sized structure, propagate in the microtwin structure. It is demonstrated that these microstructure characteristics ensure a multiple (by 3–5 factors) yield strength increase at 20 and 650°C.