Effect of grain boundary segregations of Fe, Co, Cu, Ti, Mg and Pb on small plastic deformation of nanocrystalline Al

Abstract

The paper studies the effect of grain boundary (GB) segregation of impurity atoms (Fe, Co, Cu, Ti, Mg and Pb) on the stress–strain relations of nanocrystalline Al and its alloys subjected to both shear plastic deformation and hydrostatic pressure at room temperature using molecular dynamics (MD) simulations. It is found that the GB segregations of Fe and Co atoms in the nanocrystalline Al–Fe and Al–Co alloys, respectively, strengthen their GBs, while those of Cu and Pb atoms in GBs of the nanocrystalline Al–Cu and Al–Pb alloys have the opposite effect. Furthermore, the GB strengthening effect of the mentioned impurity atoms in both twist and tilt GBs of Al bicrystals are analyzed via molecular statics (MS) simulations. Similar to the MD simulations, the results show that the GB segregations of Co atoms have a noticeable positive effect on the strength of the GBs while those of Pb atoms have a negative effect. Moreover, both MD and MS studies reveal that the Co, Mg and Pb atoms tend to occupy GBs of polycrystalline Al, while Ti, Fe and Cu atoms do not.