Multiscale Computational Modeling of Deformation Mechanics andIntergranular Fracture in Nanocrystalline Copper

The material description is based on two constitutive elements, the grains (or bulk crystals) and the grainboundaries (GBs), both having their behavior determined atomistically using the quasicontinuum (QC) method by simulating the plastic deformation of [110] tilt crystalline interfaces undergoing simple shear, tension and nano-indentation. Unlike our previous work [V. Péron-Lührs et al., JMPS, 2013] however, the GB thickness is here calibrated in the model, providing more accurate insight into the GB widths according to the interface misorientation angle. In this contribution, the new two-scale model is also validated against fullyatomistic
NC simulations tests for two low-angle and high-angle textures and two grain sizes. A simplified
strategy aimed at predicting the mechanical behavior of more general textures without the need to run more QC simulations is also proposed, demonstrating significant reduction in computational cost compared to full atomistic simulations. Finally, by studying the response of dogbone samples made of NC copper, we show in this paper that such a two-scale model is able to quantitatively capture the differences in mechanical behavior of NC metals as a function of the texture and grain size, as well as to accurately predict the processes of inter-granular fracture for different GB character distributions. This two-scale method is found to be an effective alternative to other atomistic methods for the prediction of plasticity and fracture in
NC materials with a substantial number of 2-D grains such as columnar-grained thin films for micro-scale electro-mechanical devices.