The Effect of Grain Boundaries on the Evolution of Microstructure in Metal Nanocomposites

Nanocomposite metals are far-from-equilibrium microstructures on account of the high area per unit volume of interfaces they contain. The associated high interface energy density drives extensive evolution of the microstructure, especially at elevated temperatures. We integrate experiments and phase field simulations to investigate the mechanisms of coarsening in a model, Nb-Cu-Nb trilayer, with the middle Cu layer terminating along a straight edge within the Nb matrix. In the absence of grain boundaries, phase field simulations predict that the edge of the terminated Cu layer retracts upon annealing. However, experiments show that the edge is anchored by grain boundaries in Cu and Nb and does not retract. Instead, it breaks up <i>via</i> grooving. Our work shows that phase field models must incorporate the influence of grain boundaries to predict microstructure evolution in nanocomposite metals.