THE ROLE OF INTERFACIAL ENERGY IN CRYSTALLITE REORIENTATION BY TWINNING

Based on the results of annealing experiments, inside and outside the electron microscope, a new mechanism has been found for the reorientation of particles on a monocrystalline substrate. Silver particles sintered on the (110) surface of a nickel substrate such that (110)[111BAR]Ag parallel-to (110)[111BAR]Ni were reoriented by the nucleation and growth of annealing twins. All of the growing twins were of one variant. Twins of other orientations did not nucleate, and in particles that contained them before sintering, they did not grow. The driving force for twinning comes from the reduction in the particle/substrate interfacial free energy. These observations are consistent with the hierarchy of Ag/Ni interfacial energies as calculated with the embedded-atom method. The ramifications of the results are discussed for annealing twins and for epitaxy.