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

Abstract

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 9 10 À5 to 3.16 9 10 À3 s À1 . The steel exhibited three-stage work hardening behavior in the variations of hr d with r d , where hr d is the product of instantaneous work hardening rate, h (h = dr d /de p ) and flow stress contribution from dislocation (r d ), and e p is the true plastic strain. The threestage work hardening was characterized by a gradual increase in hr d at low stresses (transient stage) followed by a linear increase in hr d in stage-II and inverted parabolic hardening at high r 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.

High Temperature Plastic Instability and Dynamic Strain Aging in the Tensile Behavior of AISI 316 Stainless Steel

“…Recent works [5][6][7][8][9][10][11] corroborate the existence of work hardening stages in AISI 316 steel from room temperature up to 750°C. In particular, Choudhary and Christopher 5,7 as well as Christopher and Choudhary 6,8 disclosed the existence of three work hardening stages in each tensile curve.…”

“…In Figure 2(b), for the ultimate stress, a significant increase occurred in the base line from 200 to 600°C. This increase in the ultimate stress has been attributed to DSA in 316 steels [4][5][6][7][8][9] . However, details of the DSA peaks were not discussed so far.…”

“…. These instabilities, particularly the more uniform serrations, are associated with DSA [6][7][8][9]13 . Other manifestations are revealed in terms of the temperature dependence of related tensile properties.…”

“…In particular, Choudhary and Christopher 5,7 as well as Christopher and Choudhary 6,8 disclosed the existence of three work hardening stages in each tensile curve. Stage II was found to suffer a noticeable influence of DSA in terms of an increase in dσ/dε vs. σ in the interval from 200°C to 650°C.…”

Relevance of Dynamic Strain Aging under Quasi-Static Tension on AISI 304 Stainless Steel

“…However, it was not possible to determine activation energies associated with atomistic mechanisms. Recent works on 316 steel [15][16][17][18] related both anomalous variation in the work hardening parameters with strain rate and temperature as well as plastic instabilities and serrations with DSA.…”