Various steel microstructures contain carbides that are designed to enhance the strength of the material. In
Reactor Pressure Vessel (RPV) steel, the carbides are an inherent part of the microstructure, finely distributed
throughout the grains and grain boundaries. This work focuses on the investigation of the effect of carbides
ranging from 80 nm to 1 μm on strain and stress localization when the carbides are explicitly introduced in
polycrystalline models. Two size dependent crystal plasticity finite element models are used in the investigation
to evaluate their feasibility to address localization phenomena with carbide strengthened microstructures. We
analysed the effects of carbides on quasi-2D Scanning Electron Microscopy (SEM) based microstructures with
realistic carbide mapping, and utilized synthetic 3D computational grain-carbide microstructures to investigate
spatial and shape effect of carbides. Microscale digital image correlation (uDIC) measurements show that
strain localization is influenced significantly by carbide networks and carbides can promote slip in grains
with low Schmid’s factor. Lastly, we demonstrated the effect of large carbides on fracture predictions using a
newly developed microstructurally informed brittle fracture model, which represents a step forward compared
with existing Beremin-type approaches. It was observed that carbide induced stress/strain heterogeneity alters
fracture probability predictions notably.

Various steel microstructures contain carbides that are designed to enhance the strength of the material. In
Reactor Pressure Vessel (RPV) steel, the carbides are an inherent part of the microstructure, finely distributed
throughout the grains and grain boundaries. This work focuses on the investigation of the effect of carbides
ranging from 80 nm to 1 μm on strain and stress localization when the carbides are explicitly introduced in
polycrystalline models. Two size dependent crystal plasticity finite element models are used in the investigation
to evaluate their feasibility to address localization phenomena with carbide strengthened microstructures. We
analysed the effects of carbides on quasi-2D Scanning Electron Microscopy (SEM) based microstructures with
realistic carbide mapping, and utilized synthetic 3D computational grain-carbide microstructures to investigate
spatial and shape effect of carbides. Microscale digital image correlation (uDIC) measurements show that
strain localization is influenced significantly by carbide networks and carbides can promote slip in grains
with low Schmid’s factor. Lastly, we demonstrated the effect of large carbides on fracture predictions using a
newly developed microstructurally informed brittle fracture model, which represents a step forward compared
with existing Beremin-type approaches. It was observed that carbide induced stress/strain heterogeneity alters
fracture probability predictions notably.