Fragmentation of the edge of a terminated Cu nanolayer within a Nb matrix upon annealing

We investigate the evolution of the tip of a terminated Cu nano-layer embedded within a Nb matrix upon annealing at 800°C. The tip of the terminated Cu layer fragments progressively into a series of single-crystal Cu particles upon continued annealing. This finding shows that layer fragmentation is the second step, after layer pinchoff, in the thermal coarsening of nanolayered metal composites. Comparison to prior phase-field modeling permits us to infer that the mobility at 800°C of Cu-Nb, as modeled by the Cahn-Hillard equation, is M(c)=(M0=7.3±3.6nm5/s·eV)|1−c2|, where the order parameter, c, is 1 for Cu and -1 for Nb.