First-principles study of the stability and interfacial bonding of tilt and twist grain boundaries in Al and Cu

Abstract

Nature of grain boundaries (GBs) should affect the micro-structural evolution and mechanical properties of metallic micro-crystalline formed by severe plastic deformation. The stability and interfacial bonding of coincidence tilt and twist GBs in Al and Cu have been examined by using the projector-augmented wave method within the density-functional theory. For the {221} ∑ = 9 tilt boundary, glide models are more stable than mirror models for Al and Cu, and the (001} ∑ = 5 twist boundary is more stable than the ∑ = 9 tilt boundary for Al and Cu, due to smaller structural distortions. There is a tendency that the boundary energies in Al are substantially smaller than those in Cu. This can be explained by the electronic and atomic behavior of bond reconstruction at the interfaces in Al, due to the covalent nature of Al as observed in the charge density distribution, in contrast to rather simple metallic bonding at Cu GBs. © 2009 The Japan Institute of Metals.