The development of advanced creep constitutive equations for high chromium steel P91at low stress range

Diffusion dominates the creep deformation at low stress range for high chromium steel P91. Brittle creep fracture is caused by cavity nucleation, growth and coalescence of cavities and large precipitates (Laves phase and M23C6) at grain boundary under low stress range. At low stress range, a linear relation between strain at failure and different stresses has been described. Moreover, the minimum strain rate is also proportional to the different stresses. The new set of constitutive equations model should describe the microstructure evolutions of M23C6 carbides and Laves phase, the linear relationships between strain rate and stress, strain at failure and stress. The both influence of stress and microstructural changes is regarded as the new failure criterion. Three aspects of novelty for the new set of constitutive equations model have been considered in this paper. The further work should focus on the form and validation of the new set of constitutive equations model.