CAREER: Understanding novel characteristics of defects in concentrated solid solutions from first principles calculations

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Nontechnical Summary:Mechanical properties, such as strength and fracture resistance, of metal alloys are governed by crystal defects-e.g dislocations, grain boundaries, and solutes. Designing new metal alloys, with enhanced properties, requires detailed knowledge of the properties of these defects. This project provides a new understanding of the structural defects and plasticity in high entropy alloys, a new class of multicomponent alloys with desirable and nonconventional properties. The research program stimulates the study of complex multi-component alloy compositions that have never been considered before, creating a great potential for discovery of new materials to address the ever-increasing technological needs of the twenty-first century such as energy and efficient transportation. In addition, novel properties of high entropy alloys encourages new ways of viewing fundamental aspects of physical metallurgy, yielding new insights that are applicable to a wide range of metallic alloys. The integrated research and educational program seeks to "advance discovery and understanding while promoting teaching, training, and learning" to train the next generation of diverse and globally competitive research scientists and engineers. The educational component, drawing from the research theme, enhances teaching/learning of difficult materials science concepts using simulations. In addition, the outreach activities establishes a connection between the PI and Columbus School for Girls (CSG), a local all-girls K through 12 school in Columbus, Ohio, to encourage and mentor young women towards career paths in science and engineering fields.Technical Summary:This CAREER project aims to understand the fundamental deformation mechanisms responsible for the remarkable mechanical properties of high entropy alloys (HEAs), a class of multicomponent metallic alloys in (near) equal atomic percent that, strikingly, crystalize as single-phase solid solutions. The research goal of this proposal is to test the hypothesis that the atomic-scale deformation mechanisms in single-phase, concentrated multi-element alloys (CMAs) "of which the single phase HEAs are an interesting subset" are fundamentally different from those in dilute alloys. The specific objectives are: (1) Computing dislocation and stacking fault structures and energies in CMAs with density functional theory (DFT). (2) Developing new computational tools that enable dislocation modeling in CMAs with DFT. (3) Generating a new solid solution strengthening model applicable to CMAs. The outcomes of this proposal are not restricted to specific CMAs and are applicable to the broad category of concentrated solid solutions, providing new ways of thinking about fundamental aspects of physical metallurgy and yielding new insights that are applicable to a wide range of metallic alloys with new compositions for tailored properties.The education and outreach goals of this proposal are (i) to enhance teaching/learning of materials science via simulation-based visualizations and (ii) to increase the representation of women and minorities in science and engineering careers. These goals are achieved via (1) creating and disseminating short videos on atomic-scale deformation mechanisms, as course enrichment modules at various levels and (2) providing mentorship, research opportunities and hands-on activities for K-12 students in Columbus School for Girls-- a local all-girls K through 12 school.