Analytical homogenization modeling and computational simulation of intergranular fracture in polycrystals

Failure at grain boundaries has a critical effect on the overall fracture behaviour of polycrystalline aggregates, as is the case in many metals. In the case of dynamic embrittlement, segregation of impurities occurs at grain boundaries, lowering their cohesive strength. The material response is then dominantly determined by grain boundary properties. The self-consistent scheme is extended to account for grain boundary decohesion by using a cohesive law to represent crack initiation and propagation. After introducing the imperfect interface conditions into the Eshelby's equivalent inclusion solution, the effective tensile response and brittle intergranular fracture of a Cu-Ni-Si alloy is predicted. The proposed analytical model allows for the identification of parameters for both crystal plasticity and cohesive constitutive laws, from a single macroscopic tensile curve. Afterwards, multiscale computations of artificial microstructures are done using the analytically calibrated values of material parameters. Comparison of the results with experimental data shows a satisfactory agreement.