Cu was known as one of the harmful tramp elements in recycled Fe. In the present work, the effects of Cu on Fe grain boundary embrittlement were investigated by first-principles tensile tests. Because the Fe–Cu bonds were rather isotropic and the effects due to their difference in atomic size were negligibly small, the grain boundary atomic structure prior to straining was little changed by Cu segregation. However, the Fe–Fe bond around the Cu atom was weakened due to charge transfer from the Fe atom to the Cu atom, and premature bond breaking occurred at the weakened Fe–Fe bond, resulting in an enhancement of grain boundary embrittlement by Cu segregation. The s and p electrons played a vital role in the charge transfer.

Effects of Segregated Cu on an Fe Grain Boundary by First-Principles Tensile Tests. M.Yuasa, M.Mabuchi: Journal of Physics - Condensed Matter, 2010, 22[50], 505705