We have synthesized Cu/Nb nanolayered metallic composites containing interfaces that have 3D character (3D Cu/Nb) to study their effect on mechanical behavior. 3D interfaces are defined as having atomic-scale structural gradients in the direction normal to the plane that defines them. Nanolayered composites are suited to this effort because their high interfacial content causes their properties to be dominated by their interfacial structures. Cu/Nb is an often-used model system due to the immiscibility of its components and ability for it to be sputtered with control over heterophase interface structure. Thin film samples were deposited using magnetron sputtering with layer thicknesses ranging from 10 to 80 nm, and an interfacially graded region 10 nm thick. Techniques such as continuous stiffness measurement (CSM) Berkovich nanoindentation and micropillar compression at various orientations with respect to interface plane normal were used to measure flow stress/hardness and deformability in these materials. TEM sections were taken out of deformed material to identify modes of strain localization associated with 3D interfaces. 3D Cu/Nb is shown here to be significantly harder than Cu/Nb containing interfaces with limited 3D character (2D Cu/Nb), while being softer in Berkovich indentation below a critical length scale. We will show that enhanced mechanical performance is caused by the effect that underlying deformation mechanisms have on observed modes of strain localization. In 2D Cu/Nb, ductility under micropillar compression is limited by the formation of stable shear bands that are mediated by easy shear at interfaces. Deformation of 2D Cu/Nb in nanoindentation is mediated by a few different dislocation-based mechanisms that dominate at different length scales. We conclude that a different set mechanisms mediate shear localization in 3D Cu/Nb, which we relate to the length-scale dependence of its flow stress and Berkovich nanohardness.

Mechanistic origins of enhanced mechanical properties in 3D interface Cu/Nb nanolayered metallic composites

The Virtual Technical Meeting of the Society of Engineering Science 2020 is the first fully virtual meeting of the SES community to envision and connect during the hiatus created by Covid-19, providing a platform for the exchange of ideas, and to showcase the latest research in the field of engineering science.

[Visit the Programme](https://drive.google.com/file/d/1BoCPBzrr1IQFANuzQI8a-paXCJoOcCkB/view?usp=sharing) | [Visit the Prerecorded Video/Poster List](https://drive.google.com/file/d/1XHLeEXJxEFjCSsNScuLDfMwy1X7oy7oJ/view?usp=sharing) | [View the Session Grid](https://drive.google.com/file/d/1VeDOC-Ev5m_ymYjXnjaXSZHR3_DARiLt/view?usp=sharing)