A grain level model for deformation and failure of ultrafine-grained tungsten

Ultrafine-grained tungsten (UFG W) produced by severe plastic deformation technology has many potential applications due to its high strength and ductility. To reveal the mechanism for the high ductility of UFG W, the deformation and failure behaviors of coarse-grained tungsten (CG W) and UFG W have been compared based on a three-dimensional crystal plastic finite element method (CPFEM) simulation. Cohesive element method has been utilized to model the behavior of grain boundaries (GBs). Both plastic deformation in grain interiors and grain boundary opening have been observed in different periods of deformation in UFG W. It is concluded that the high GB density and elongated microstructure in the UFG W suppress crack propagation, decrease the stress concentration and impurity concentration on GBs, therefore enhance the ductility of the material.