Dr. Youxing Chen
Assistant professor
Department of Mechanical Engineering and Engineering Science
University of North Carolina at Charlotte

Abstract

Concentrated solid solution alloys (CSAs) composed of multiple components, especially high entropy alloys consisting of three or more elements, have provided new avenues for materials design. Due to their superior mechanical properties and radiation tolerance, these alloys are highly promising candidates for use in advanced fission and fusion reactors. However, the design of radiation-resistant materials requires an understanding of the early-stage radiation-induced damage in CSAs, including defect generation and accumulation. Measuring point defects and low-density dislocations is challenging, particularly when the radiation penetration depth is shallow. Nanoindentation is a unique technique for probing surface mechanical properties at the micrometer and sub-micrometer scales, especially when dealing with a large alloy design space (such as in CSAs). In this study, we focused on three types of single-crystal CSAs, namely NiCo, NiFe, and NiCoFeCr, with the same crystallographic orientation of (100) surface planes for low-dose irradiation. This approach enabled us to eliminate microstructural and grain orientation effects. Our nanoindentation results and analysis clearly demonstrate distinct strengthening in NiCo, NiFe, and NiCoFeCr prior to radiation, as well as low-dose radiation-induced hardening. We successfully extracted the density of geometrically necessary dislocations and statistically stored dislocations and compared them quantitatively to investigate the interaction between irradiation-induced defects and geometrically necessary dislocations.

Biography

Dr. Youxing Chen is an assistant professor in the Department of Mechanical Engineering and Engineering Science at the University of North Carolina at Charlotte. His research focuses on developing structural materials capable of withstanding extreme environments, such as radiation and high temperatures. Dr. Chen’s research group is particularly interested in (1) understanding the deformation and failure mechanisms of advanced alloys, including high-entropy alloys; (2) developing advanced nanomechanical testing methods, such as nanoindentation or in situ microscale/nanoscale testing in an electron microscope, for measuring properties at a small scale; and (3) exploring additive manufacturing of ceramics or metallic composites. Dr. Chen earned his PhD from Texas A&M University and worked as a postdoctoral associate at Los Alamos National Laboratory. He has authored 68 peer-reviewed journal articles, including 20 as the first author or corresponding author on prestigious journals such as Nature Communications. According to Google Scholar, his work has received 2230 citations, and his h-index is 27.

Thursday, March 30. 2023
4:00 pm seminar

Hybrid Option  (Speaker is in person)

zoom (link upon request)
or
Room 1202 Burlington Labs