Kinetics of Uniaxial Tensile Flow and Work Hardening Behavior of Type 316L(N) Austenitic Stainless Steel in the Framework of Two-Internal-Variable Approach

摘要

Uniaxial tensile flow and work hardening behavior of type 316L(N) austenitic stainless steel have been examined in the framework of two-internal-variable approach based on the evolution of forest dislocation density and mean free path with plastic strain in the temperature range from 300 K to 1023 K (27 °C to 750 °C) and strain rates ranging from 3.16 × 10−5 to 3.16 × 10−3 s−1. The steel exhibited three-stage work hardening behavior in the variations of θσ d with σ d, where θσ d is the product of instantaneous work hardening rate, θ (θ = dσ d/dε p) and flow stress contribution from dislocation (σ d), and ε p is the true plastic strain. The three-stage work hardening was characterized by a gradual increase in θσ d at low stresses (transient stage) followed by a linear increase in θσ d in stage-II and inverted parabolic hardening at high σ d in stage-III. At all the strain rate and temperature conditions, the flow and work hardening behavior was appropriately described by the two-internal-variable model. The work hardening parameters such as dynamic recovery parameter and final mean free path, and the predicted forest, mobile, and total dislocation densities at uniform plastic strain exhibited three distinct temperature regimes. Anomalous variations in the work hardening parameters with respect to temperature and strain rate observed at intermediate temperatures have been ascribed to the occurrence of dynamic strain aging. At high temperatures, dominance of dynamic recovery has been observed.