Three dimensional thinking: Effects of atomic interfacial structure on nanolaminate mechanical behavior

Bimaterial nanolamellar composites have been studied extensively to probe the influence of interface structure on mechanical properties in nanocrystalline alloys. We will show that nanolaminates incorporating 3D interfaces (3D Cu/Nb, Ti/TiN, Ti/Nb) containing chemical, crystallographic, and structural nanoscale heterogeneities in all spatial dimensions have remarkable strength and deformability compared to 2D interface counterparts. In this study, multilayered composites containing either chemically abrupt interfaces, or an interfacial gradient were deposited via magnetron sputtering. Spherical and Berkovich nanoindentation determines hardness, modulus, and indentation stress-strain behavior as a function of layer thickness and interface structure. In-situ SEM micropillar compression shows that nanocomposites containing 3D interfaces have superior behavior under uniaxial compression. Transmission Electron Microscopy reveals the structural gradient between the pure phases. We discuss strengthening effects in terms of the interplay between layer thickness, atomic interfacial structure and chemistry, and dislocation-based mechanisms.