Multiscale modeling of nanoscale metallic multilayers

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We use computational techniques to understand the fundamental mechanisms of deformation in nanoscale metallic multilayers at small time and length scales and investigate the effect of parameters such as interface structure, chemical composition, and morphology on these mechanisms. We use multiscale models of atomistic simulations, monte carlo methods, crystal plasticity, and continuum mechanics for deformation mechanisms of composite multilayers and provide mathematical models to determine the collective behaviors of these materials at various length scales.

Computational prediction of the structure of semicoherent interfacesGraphic image.

Solid-state interfaces are ubiquitous in materials science: from grain boundaries in polycrystalline metals to heterophase interfaces in multi-component, multi-functional composites . As awareness of their far-reaching influence on materials behavior grows, so does interest in predicting and controlling their structure and properties. In this project, we advance the dislocation-based model for interface structure by developing a method for determining the unique reference state in which interface Burgers vectors must be defined.

Nanoporous materials

Graphic image.Nanoporous (NP) metals are three-dimensional networks of inter-connected pores and ligaments. Their open-cell structure and high surface area per unit volume give them unique electrical, mechanical, and catalytic properties as well as high radiation resistance. The deformation behavior of NP materials are often controlled by their microstructure including porosity and size and shape of the ligaments. The goal of this project is to reveal the mechanisms that control the plastic deformation of NP metals and develop predictive models/maps for determining their mechanical properties including ductility and strength.

Composite pseudoelastic nanowires

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Related article: Stress-assisted structural phase transformation enhances ductility in Mo/Cu bicontinuous intertwined composites

Metallic nanowires can recover from up to 50% of plastic strain when their cross-sectional area is smaller than a certain critical value, which is on the order of a few nms. This behavior is called pseudoelasticity and the mechanism responsible for it is the formation of partial dislocations (twinning). We particularly explore the coupled effects of geometry and coherent interface on the tendency of composite nanowires to deform via twins and show pseudoelastic behavior. The idea of sandwiching nanowires can be used in the case of metals with low twinability to improve their ductility and pseudoelastic properties in future.