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

该奖项支持研究，以了解一种新颖的、可扩展的表面变形工艺，以实现金属中梯度纳米晶体微结构的受控创建。梯度纳米结构金属是一种新型的结构材料，与传统的粗晶金属或块体纳米结构金属相比，具有更好的强度和塑性组合。这项研究旨在通过研究一种新的变形工艺来克服产生具有可控空间晶粒度梯度的金属表面的主要工艺障碍，该工艺利用表面塑性“波”的可控传播。这项研究将对美国制造业产生影响，为高效制造这种新型材料提供科学知识，使其在包括汽车和航空航天在内的广泛关键应用中具有性能优势。该项目的教育相关影响包括通过在国家实验室实习对研究生进行基于变形的加工方法的培训，为加强本科生和研究生教育而开发的材料加工课程，以及开发基于可视化的材料制造教育工具，以培养人们对STEM相关领域的广泛兴趣。该项目旨在研究两种材料改性过程：通过在金属表面重复创建和传播塑料波来控制大表面上的地下应变分布的能力；以及通过控制亚表面应变分布来设计具有可调颗粒尺寸梯度和纳米结构层厚度的表面的能力。为了实现这些目标，一个来自多个机构的跨学科团队将在以下领域开展合作研究：(1)表面塑性流动和表面应变映射的现场分析，(2)变形-微结构相关性，(3)极端塑性应变和应变梯度下表面塑性和微结构演化的预测建模，以及(4)力学性能表征。综上所述，这些研究活动将有助于建立对以可扩展方式实现梯度纳米结构金属和金属表面所必需的工艺-微观结构-性能关系的全面科学理解。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.