Interface-coupling-dependent mechanical behaviors of sandwich-structured Ni/Cu/Ni composites

Abstract

Maximizing the interface coupling effect is a key to improve mechanical properties of laminate/gradient structures. In this work, Ni/Cu/Ni sandwich-structured composites with the middle Cu layers cyclically deformed to different cycles were fabricated to investigate the influence of initial dislocation density on the interface-coupling-dependent mechanical behavior. Extra yield strength contributed by the interface coupling was found to decrease with decreasing the degree of mechanical incompatibility across the interface during uniaxial tensile loading. In addition, the width of geometrical necessary dislocation (GND) pile-up regions adjacent to the interfaces was observed to decrease with increasing the initial dislocation density of Cu layers, which is attributed to the change of source-obstacle configuration in the stress gradient model. These findings suggest that the GND strengthening effect caused by the interface coupling and the cyclic hardening effect in the constituent layers appears to be competitive, and the interface coupling effect is gradually weakened with increasing the initial dislocation density of Cu layers.