Mechanistic Modeling of Dynamic Strain Aging in Austenitic Stainless Steels

On the basis of experimental data from tensile testing and review of the literature, the mechanisms of dynamic strain aging (DSA) in austenitic stainless steels have been evaluated. It is concluded that, in the lower temperature range of DSA, reorientation of carbon- or nitrogen-vacancy pairs occurs, with a preferential concentration where dislocations decelerate or are temporarily arrested. This mechanism is controlled by vacancy concentration and by vacancy diffusion to crystallographic defects. DSA is absent at intermediate temperatures because there are no regions with a higher concentration of pairs, owing to the higher mobility and greater equilibrium concentration of vacancies. At higher temperatures, where serrated flow is again observed, carbon or nitrogen atoms or carbon- or nitrogen-vacancy pairs have sufficient mobility to once more produce areas of higher point defect concentration where dislocations decelerate. At still higher temperatures, DSA disappears because of the increase in carbide precipitation.