Abstract
All grain boundaries are not equal in their predisposition for fracture due to the complex coupling between lattice geometry, interfacial structure, and mechanical properties. The ability to understand these relationships is crucial to engineer materials resilient to grain boundary fracture. Here, a methodology is presented to isolate the role of grain boundary structure on interfacial fracture properties, such as the tensile strength and work of separation, using atomistic simulations. Instead of constructing sets of grain boundary models within the misorientation/structure space by simply varying the misorientation angle around a fixed misorientation axis, the proposed method creates sets of grain boundary models by means of isocurves associated with important fracture-related properties of the adjoining lattices. Such properties may include anisotropic elastic moduli, the Schmid factor for primary slip, and the propensity for simultaneous slip on multiple slip systems. This approach eliminates the effect of lattice properties from the comparative analysis of interfacial fracture properties and thus enables the identification of structure-property relationships for grain boundaries. As an example, this methodology is implemented to study crack propagation along Ni grain boundaries. Segregated H is used as a means to emphasize differences in the selected grain boundary structures while keeping lattice properties fixed.
Highlights
This manuscript proposes a methodology to isolate the influence of grain boundary structure on fracture-related properties, namely the tensile strength and the work of separation of grain boundaries using atomistic simulations
Instead of constructing sets of grain boundary models within the misorientation/structure space by varying the misorientation angle between bounds around a fixed misorientation axis, sets of grain boundaries for comparison of their mechanical properties are created by means of isocurves associated with important fracture-related properties of the adjoining lattices
Several lattice properties are proposed, and two grain boundaries with matching elastic stiffness and Schmid factor for primary slip are selected for comparison as an illustration of the selection methodology
Summary
This manuscript proposes a methodology to isolate the influence of grain boundary structure on fracture-related properties, namely the tensile strength and the work of separation of grain boundaries using atomistic simulations. The structure-tensile strength relationship is recognized to be associated with coupling between the grain boundary mechanical attributes of the adjoining lattices and its structure Both the grain boundary selection approach and the cohesive zone volume element approach to extract a density of (λ, σyy) states could be used for various geometries and simulation setups. The grain boundary selection methodology presented in this manuscript is largely independent of the means by which fracture simulations are conducted Usage of this method could be extended to cylindrical or spherical geometries, different ensembles, and boundary conditions. It is expected that the insights from such approach will play a critical role in how phase and grain boundaries should be modeled and understood
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