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

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.