Size effect and boundary type on the strengthening of nanoscale domains in pure nickel

A series of large-scale molecular dynamics simulations were carried out to investigate the interactions between an extended edge dislocation (1/2<112>{111}) and nanoscale domains in pure nickel. The pinning strength of nano-domains and the corresponding atomistic interaction mechanisms were found to be closely related to the domain boundary type, the domain size and spacing. The pinning strengths were found to be higher for high-angle domains than those for low-angle domains at the same size scale, and increase with increasing domain size and decreasing domain spacing. Unlike the by-pass via interactions between the dislocation and boundaries for high-angle domains (much like the role of hard precipitates in alloys), the dislocation was found to cut partly through the low-angle domains. Thus the dragging force from the boundary segments of the low-angle domains should be smaller when compared to the Orowan's strengthening for “hard particles”, such as high-angle domains. The predictions from Ashby's model on Orowan's strengthening are higher than the simulation data for low-angle domains, while agree relatively well with those for high-angle domains. Moreover, a more universal model was proposed to connect the dislocation line shape at the critical shear strain with the pinning strength.