Phosphorus grain boundary segregation under an intermediate applied tensile stress in a Cr-Mo low alloy steel

Phosphorus grain boundary segregation under an intermediate applied tensile stress of 200 MPa at 520 °C in a 0.025 wt.% P-doped 2.25Cr1Mo steel, which has already been thermally equilibrated, is observed using Auger electron spectroscopy. The segregation during stress ageing has a non-equilibrium nature. There are two phosphorus segregation peaks over its thermal equilibrium level, and between them there is a depletion trough of phosphorus below its thermal equilibrium level. The first segregation peak is mainly caused by the vacancy-phosphorus complex effect and the second one by the diffusional creep effect. The depletion trough of phosphorus at the initial creep stage may be attributed to the strain hardening bias effect.