Calculation of the Atomic Structure of Grain Boundaries in Metals and Alloys

Abstract

ABSTRACTThis paper reports two applications of computer simulations based on the embedded atom method to the structure of grain boundaries. First, the equilibrium segregation at symmetric twist grain boundaries in Ni-Cu alloys is computed. These simulations include both compositional rearrangements and atomic displacements. It is found that Cu segregates to the boundary and that the change in composition is confined to a few atomic layers near the boundary. The degree of segregation was found to be greater for Ni-rich alloys and for large angle boundaries. The variation of the concentration within the planes parallel to the boundary for a low angle twist boundary is studied and the variations are correlated with the positions of the boundary dislocations. The second application addresses the possibility of structural disorder in the Σ5(001) twist boundary in Au. These results show that defects corresponding to local motion of the boundary normal to the interface are low in energy. The energetics of these defects are then mapped onto the body-centered-solid-on-solid model of surface roughening. This model predicts that a roughening transition will occur in this grain boundary at 100 K or 500 K depending on the choice of interatomic interactions. The effect of this roughening transition on the x-ray scattering from the boundary is also computed.