Controlled dynamics of grain boundaries in binary alloys

Grain boundary motion of binary alloys is investigated experimentally using an organic alloy model system succinonitrile–coumarin152. In a temperature gradient, the grain boundaries drift toward the high temperature region in addition to grain boundary migration due to grain coarsening. We found that the grain boundary drift speed V depends on temperature gradient G and temperature T as V = DG/{(1 - k)(T0 - T)}, where D is the diffusion coefficient, k is the segregation coefficient, and T0 is the melting point of the pure succinonitrile. We show that the grain boundary orientation can be controlled by applying a local temperature gradient through UV or laser heating. In bulk samples, local heating of the interior is generated using two-photon absorption and imaged with a laser scanning microscope.