Microstructural modeling of P91 martensitic steel under uniaxial loading conditions

The changing face of power generation and the increasingly severe conditions experienced by power plant materials require an improved understanding of the deformation and failure response of power plant materials. Important insights can be obtained through computational studies, where the material microstructure is explicitly modeled. In such models, the physical mechanisms of deformation and damage can be represented at the microscale, providing a more accurate prediction of material performance. In this paper, two approaches are examined to represent the microstructure of a martensitic power plant steel (P91). In one approach, the model is based on a "measured microstructure" with electron backscatter diffraction (EBSD) employed to obtain the orientation of the martensitic grain structure of the steel. The alternative approach is to use a "numerically simulated" model where the microstructure is generated using the Voronoi tessellation method. In both cases, the microstructural model is incorporated within a representative volume element (RVE) in a finite-element analysis. The material constitutive response is represented by a nonlinear, rate dependent, finite strain crystal plasticity model, with the microstructural orientation specified at each finite-element integration point by the microstructural model. The predictions from the two approaches are compared. The stress distributions are observed to be very similar, though some differences are seen in the strain variation within the RVE.