On the effect of intergranular nanocracks on the shear-coupled migration of tilt boundaries

In this work, we present molecular dynamics simulations of the shear-coupled migration behaviour of symmetrical tilt boundaries Σ 17(530)/[001] perturbed by the presence of nanocracks lying on the grain boundary. The simulations were performed for copper bicrystals at 300 K. The focus has been on the study of crack size effects. The simulations were carried out using the embedded atom method with temperature control. Systems of constant width, X, and different crack sizes, 2a, were generated at 0 K. The ratio 2a/X characterizes the system. Periodic boundary conditions were set along the direction of application of the load and the tilt axis. After relaxation, the virtual shear of the bicrystals was carried out at a constant rate of 10(8) s-1. The response of the cracked specimens can be divided into: (i) shear-coupled migration of the grain boundary with increasing applied shear stress, (ii) intergranular propagation of the crack and (iii) emission of dislocations and closing of the grain boundary dislocation loop. Neste trabalho, apresentamos simula es de dinamica molecular do comportamento de migra o duma fronteira de gr o acoplada à aplica o duma tens o de cisalhamento no caso duma fronteira simétrica de flex o Σ17(530)/[001] perturbada pela presen a de nanofendas na própia fronteira de gr o. As simula es foram realizadas para bicristais de cobre a 300 K. O interesse do estudo é o efeito do tamanho da fenda. As simula es foram realizadas utilizando o embeddedatommethod com controlo de temperatura. Sistemas de largura constante, X, e tamanhos de fendas diferentes, 2a, foram gerados a 0 K. A raz o 2a/X caracteriza o sistema. Condi es de fronteira periódicas foram estabelecidas ao longo da dire o de aplica o da carga e do eixo da fronteira simétrica de flex o. Após o relaxamento, o cisalhamento virtual dos bicristais foi realizado a uma taxa constante de 10(8) s-1. A resposta das amostras fissuradas pode ser dividida em: (i) ao cisalhamento acoplado a migra o do limite de gr o com o aumento da tens o de cisalhamento aplicada, (ii) propaga o intergranular da fenda e (iii) emiss o de desloca es e forma o de desloca es em anel.