Analysis of Tensile Stress-Strain and Work-Hardening Behavior in 9Cr-1Mo Ferritic Steel

Detailed analysis on tensile true stress (sigma)-true plastic strain (epsilon) and work-hardening behavior of 9Cr-1Mo steel have been performed in the framework of the Voce relationship and Kocks-Mecking approach for wide range of temperatures, 300 K to 873 K (27 degrees C to 600 degrees C) and strain rates (6.33 x 10(-5) to 6.33 x 10(-3) s(-1)). At all test conditions, sigma-epsilon data were adequately described by the Voce equation. 9Cr-1Mo steel exhibited two-stage work-hardening behavior characterized by a rapid decrease in instantaneous work-hardening rate (theta = d sigma/d epsilon) with stress at low stresses (transient stage) followed by a gradual decrease in h at high stresses (stage III). The variations of work-hardening parameters and theta-sigma as a function of temperature and strain rate exhibited three distinct temperature regimes. Both work-hardening parameters and theta-sigma displayed signatures of dynamic strain aging at intermediate temperatures and dominance of dynamic recovery at high temperatures. Excellent correlations have been obtained between work-hardening parameters evaluated using the Voce relationship and the respective tensile properties. A comparison of work-hardening parameters obtained using the Voce equation and Kocks-Mecking approach suggested an analogy between the two for the steel. DOI: 10.1007/s11661-012-1385-0 (C) The Minerals, Metals & Materials Society and ASM International 2012