Strain partitioning between matrix and precipitates during fatigue deformation of 2.25Cr–Mo steel

Abstract

The influence of stress rate [Formula: see text] on load/strain partitioning between different phases of a micro-alloyed 2.25Cr–Mo steel during stress-controlled fatigue deformation at room temperature (RT) was studied by conducting asymmetrical ratcheting fatigue tests employing [Formula: see text] values of 50–450 MPa/s. Fatigue life ( Nf) significantly reduced for tests conducted by employing [Formula: see text] = 50 MPa/s compared to 450 MPa/s, i.e. Nf = 510 and 24,983 cycles respectively. From TEM studies, it is confirmed that due to load/strain partitioning stacking faults (SFs)/micro-twin formed in M23C6 carbides during high [Formula: see text] fatigue deformation, whereas dislocation cells are formed in low [Formula: see text] fatigue deformation. A plausible explanation to account for different cycle life with change in [Formula: see text] of fatigue deformation is offered.