Creep properties, microstructural evolution, and fracture mechanism of an Al added high Cr ODS steel during creep deformation at 600°C

Abstract The creep properties, microstructural evolution, and fracture mechanism of 16Cr-3Al oxide dispersion strengthened (ODS) steel were systematically investigated at 600°C under different uniaxial tensile stresses in the range of 160-200 MPa. The minimum creep rate had a linear relationship with the mean creep rate, which followed the modified Monkman-Grant relationship with a slope of 0.57. The threshold stress was determined as 145.09MPa based on the modified Bird-Mukherjee-Dorn (BMD) equation. Both Laves phase and Cr-rich phase were identified after creep deformation. The evolution of Cr-rich phase during creep deformation included the dissolution of W-rich σ phase and the precipitation of Si-rich σ phase. Cross-sectional cracks could be observed near the rupture surface, and these cracks mainly formed near the Si-rich σ phase and the boundaries between coarse and fine grains. It was considered that the formation of Si-rich σ phase in fine grains was the main fracture mechanism of 16Cr-3Al ODS steel during creep deformation.