MSE Seminar: “Role of Fe in Long‐range Ordered Ni2Cr Precipitates in Ni‐Cr‐based Alloys”

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Julie Tucker, Ph.D.

Associate Professor, School of Mechanical, Industrial and Manufacturing Engineering
Oregon State University

Dr. Julie Tucker earned her B.S. in Nuclear Engineering from the University of Missouri – Rolla. She attended graduate school at the University of Wisconsin – Madison as a Naval Nuclear Propulsion Fellow, where she received her M.S. and Ph.D. in Nuclear Engineering with a minor in Materials Science in 2008. After graduation, Dr. Tucker spent five years as a Principal Scientist at Knolls Atomic Power Laboratory in Schenectady, NY, studying the thermal stability of structural alloys for nuclear power systems. She joined the School of Mechanical, Industrial, and Manufacturing Engineering at Oregon State University as an Assistant Professor in 2013 and was promoted to Associate Professor in 2019. In 2019 she was awarded the Dean’s Professorship and was also appointed as the Materials Science Interdisciplinary Graduate Program Director. Dr. Tucker has an active research group focused on the degradation of materials in extreme environments and alloy development. Her research efforts leverage both modeling and experimental approaches to gain a fundamental understanding of materials performance.

Abstract

Service temperatures in pressurized water reactors may promote nucleation and growth of the long‐range order (LRO) Ni2Cr phase in Ni‐based alloys. This phase transformation leads to drastic increases strength while decreasing the ductility. The formation of Ni2Cr with respect to Ni, Cr, and Fe compositions is disputed in literature. Further, the rate of formation and nucleation factors is not well established in and between model and commercial alloys. In this research, isothermal aging of Ni‐based commercial alloys: 625, 625 plus, 690, and Ni‐Cr‐Fe model alloys has been performed to quantify the impact of LRO over time at temperatures 330, 360, 418, and 475 °C, aged up to ~30k, and ~10k hours for commercial and model alloys, respectively. The alloys were characterized by Vickers hardness testing and synchrotron x-ray diffraction. Results show that hardness changes with precipitate size rather than phase fraction transformed, which plateaus at early aging times.