Unified description of tensile work hardening behaviour of P92 steel

Tensile work hardening behaviour of P92 steel has been examined over wide range of temperatures (300-923 K) and strain rates (3.16 x 10(-5)-1.26 x 10(-3) s(-1)) in terms of the variations of instantaneous work hardening rate (theta) with true stress (sigma) and true plastic strain rate ((epsilon) over dot(p)). At all the temperatures and applied strain rates, theta vs. sigma exhibited two-stage work hardening behaviour characterised by a rapid decrease in theta at low stresses (transient stage) followed by a gradual decrease at high stresses (stage-III). theta vs. sigma also exhibited three distinct temperature regimes along with signatures of dynamic strain ageing at intermediate temperatures and dominance of dynamic recovery at high temperatures. Analysis in terms of the variations of theta with (epsilon) over dot(p) displayed a unified curvilinear behaviour independent of temperature. For a given applied strain rate, a linear correlation between theta and the reciprocal of plastic strain rate (1/(epsilon) over dot(p)) was observed. As a consequence, the rate of change of true stress was observed to be directly proportional to plastic strain rate independent of temperature. Further, a unified description of tensile work hardening in terms of a master curve between work hardening rate (theta) and plastic strain rate normalised by applied strain rate ((epsilon) over dot(p)/(epsilon) over dot(a)) has been obtained for the range of strain rates and temperatures examined. (C) 2015 Elsevier B.V. All rights reserved.