Applicability of Kocks-Mecking approach for tensile work hardening in P9 steel

Work hardening behaviour of P9 steel in the temperature range 300-873 K has been examined in the framework of Kocks-Mecking (K-M) approach. At all temperatures, P9 steel exhibited two-stage work hardening behaviour characterised by a rapid decrease in instantaneous work hardening rate (i.e. theta=d sigma/d epsilon, where sigma is the true stress and e is the true plastic strain) with stress at low stresses (transient stage) followed by a gradual decrease at high stresses (stage III). Stage III work hardening of P9 steel was adequately described by K-M approach. The variations of work hardening parameters associated with K-M approach for stage III with temperature indicated three distinct temperature regimes. At all temperatures, good correlations between the respective work hardening parameters evaluated using K-M approach and from Voce equation and its derivative have been obtained for P9 steel.