Collaborative Research: Engineering Gradient Nanostructured Metals by Multi-Pass Plastic Wave Deformation

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This award supports research to understand a novel and scalable surface deformation process for enabling controlled creation of gradient nanocrystalline microstructures in metals. Gradient nanostructured metals are a new class of structural materials that possess superior combination of strength and ductility, when compared to the conventional coarse-grained metals or bulk nanostructured metals. The research specifically aims to overcome major processing barriers in generating metal surfaces with controlled spatial grain-size gradients by investigating a novel deformation process that utilizes controlled propagation of surface plastic “waves”. The research will have bearing on the U.S. manufacturing industry by providing the scientific knowledge to efficiently manufacture this new class of materials with performance benefits across a wide range of critical applications, including in automotive and aerospace. Education-related impacts of the project include training of graduate students in deformation-based processing methods via internships at national labs, materials processing curriculum development to enhance undergraduate and graduate education, and development of visualization-based tools for materials manufacturing education to foster widespread interest in STEM-related fields.The project seeks to investigate two material modification processes: the ability to control subsurface strain distribution over large surfaces through repeated creation and propagation of plastic waves across the metal surface; and the ability to engineer surfaces with tunable grain size gradients and nanostructured layer thickness via control of the subsurface strain distribution. To achieve these goals, an interdisciplinary team from multiple institutions will engage in collaborative research in the following areas: (1) in-situ analysis of surface plastic flow and surface strain mapping, (2) deformation-microstructure correlations, (3) predictive modeling of surface plasticity and microstructure evolution under extreme plastic strains and strain gradients, and (4) mechanical property characterization. Taken together, these research activities will help establish a thorough scientific understanding of the process-microstructure-property relationships essential for realizing gradient nanostructured metals and metal surfaces in a scalable manner.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.