The Influence of Deformation and Short-Term Hightemperature Annealing on the Microstructure and Mechanical Properties of Austenitic Steel 17Cr-14Ni-3Mo (316 Type)

Resumo

The deformation and thermal action on the microstructure and mechanical properties of a stable austenitic Cr-Ni stainless steel is investigated. It is shown that under deformation conditions packets of microtwins and bands of localized deformation with the inner fragmented structure are formed, where the fragments are of the submicro- and nanocrystaalline scales with low- and high-angle misorientation boundaries. These features of microstructure ensure high yield-point values ≈1100 MPa at a relative elongation of ≈6–7%. Short-term (to 150 s) high-temperature (850°С) annealing of the deformed structure gives rise to a local development of the processes of polygonization and recrystallization in the regions of strain localization bands. As a result of such annealing, packets of microtwins, strain localization bands, polygonized subgrains and recrystallized grains of primarily submicron dimensions are observed in the steel structure. The resulting structural states ensure the yield strength values up to 740 MPa at the relative elongations ≈20–28%. The physical processes taking place in the steel under the experimental deformation and annealing conditions are discussed.