CAREER: Leveraging Plastic Deformation Mechanisms Interactions in Metallic Materials to Access Extraordinary Fatigue Strength.

非技术概述：结构工程中使用的金属材料对许多工业都是至关重要的。然而，许多金属和合金对重复载荷（疲劳）的抵抗能力有限，限制了它们的可持续性。金属材料在重复载荷作用下产生纳米尺度的局部变形，最终导致裂纹萌生和断裂。在本项目中，极端温度下的预变形用于产生初始变形状态，从而阻碍重复加载下变形的局部化。首先，确定了金属材料在纳米尺度下在极端温度下的变形行为。然后，通过这种基本的理解，从极端温度变形中识别变形的状态，当材料受到重复加载时，这些变形会阻碍变形的局部化。这一努力旨在为当前的金属和合金提供竞争优势和可持续性，以满足我们社会不断发展的需求和先进的技术。技术概述：该研究旨在探索和确定金属材料中塑性变形机制的相互作用。通过关注有益的相互作用，面心立方材料可以获得显著的疲劳强度。本项目将探讨当各种变形机制竞争时塑性是如何局部化的。最先进的原位表征工具，擅长统计和定性地确定塑性局部化，用于研究金属材料内部可能的变形机制相互作用。在此基础上，引入了极端温度下的预变形路径，以创建初始塑性局部化状态，从而阻碍循环不可逆性，这是控制材料在疲劳下断裂的一个因素。通过极端温度下的形变来控制纳米尺度上的塑性局部化，可以显著提高结构金属的疲劳强度。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

NON-TECHNICAL SUMMARY:Metallic materials used in structural engineering are vital to a wide range of industries. However, many metals and alloys exhibit limited resistance to repeated loading (Fatigue), limiting their sustainability. Metallic materials under repeated loading localize deformation at the nanometer scale that ultimately leads to crack initiation and fracture. Pre-deformation under extreme temperatures is used in the present project to generate initial deformation states that hinder the localization of the deformation under repeated loading. First, the deformation behavior of metallic materials at the nanometer scale under extreme temperatures is determined. Then, through this fundamental understanding, deformation states from extreme temperature deformations that hinder the localization of the deformation when the material is subject to repeated loading are identified. This endeavor aims to equip current metals and alloys with the competitive edge and sustainability required to meet the ever-evolving needs of our society and advancing technology.TECHNICAL SUMMARY:The research initiative seeks to explore and identify the interactions of plastic deformation mechanisms in metallic materials. By focusing on beneficial interactions, remarkable fatigue strength in face-centered cubic materials can be achieved. This project will explore how plasticity localizes when various deformation mechanisms compete. State-of-the art in-situ characterization tools, adept at statistically and qualitatively determining plastic localization, is used to study the array of possible deformation mechanism interactions within metallic materials. Building on this knowledge, pre-deformation pathways at extreme temperatures are introduced to create initial plastic localization states that hinder cyclic irreversibility, a factor that governs material fracture under fatigue. By manipulating plastic localization at the nanoscale through deformation at extreme temperatures, the fatigue strength of structural metals is enhanced dramatically.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.