Creep resistance of bulk copper–niobium composites: An inverse effect of multilayer length scale

Metallic multilayer systems show promising performance in extreme environments, with high stability of bi-metal interfaces down to nanometer length scales. The creep behavior of bulk, accumulative roll bonded (ARB) Copper–Niobium (Cu–Nb) composites has been studied at 400 °C as a function of layer thickness, ranging from 2 μm to 65 nm. Similar to single phase metallic systems, three regimes are observed during creep: transient, steady-state and tertiary. The mechanism controlling minimum creep rate for all conditions tested has a strong dependence on stress, consistent with dislocation-dominated creep. Unlike the conventional effect of grain size on creep resistance, this study reveals that decreasing length scale increases creep resistance. [Display omitted]