Modelling microstructural evolution and creep behaviour of a novel martensitic 10 % Cr steel: a physics-based mean-field approach

Creep deformation significantly limits the lifespan of components in high-temperature applications, such as thermal power plants, and understanding its underlying microstructural mechanisms is essential for accurately predicting plastic deformation, which may vary considerably depending on the initial microstructure. Here, we refined a physics-based mean-field model and applied it to a novel 10% Cr martensitic steel alloy. The model is based on an initial microstructure which includes subgrain size and various dislocation density types, and on precipitate evolution obtained from MatCalc, and describes both creep deformation and microstructural evolution. To this end, we incorporated enhanced treatment of physical phenomena, such as the Zener pinning effect, refined pipe diffusion, the solute drag effect, and temperature-dependent mechanical properties. We validated our model using precipitation kinetics simulations and comprehensive experimental investigations, including electron backscatter diffraction (EBSD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), of samples in one as-received and one post-creep state (210 MPa at 600°C). The model is effective for predicting creep rates and simulating microstructural evolution, and aligns well with experimental results. Further, it offers insights into dislocation evolution and precipitate interactions, thus establishing a link between microstructure and macroscopic properties, which in turn enables multi-scale modelling. This model provides a useful tool for predicting creep behaviour and optimising high-temperature materials, and hence for guiding material design in both academic research and industrial applications.