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广泛的行业至关重要。然而，许多金属和合金对重复加载(疲劳)的抵抗力有限，限制了它们的可持续性。金属材料在反复载荷作用下，在纳米尺度上发生局部变形，最终导致裂纹萌生和断裂。在本项目中，采用极端温度下的预变形来产生初始变形状态，这些状态阻碍了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，通过这一基本理解，确定了在材料受到重复加载时阻碍变形局部化的极端温度变形的变形状态。这一努力旨在使现有的金属和合金具有竞争力和可持续性，以满足我们社会和不断进步的技术的不断发展的需求。技术摘要：该研究计划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。这个项目将探索当各种变形机制相互竞争时，塑性是如何局部化的。最先进的原位表征工具，擅长于统计和定性地确定塑性局部化，用于研究金属材料中一系列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，以创建阻碍循环不可逆性的初始塑性局部化状态，循环不可逆性是控制疲劳下材料断裂的一个因素。通过在极端温度下通过变形在纳米尺度上操纵塑性局部化，结构金属的疲劳强度显著增强。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。

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.