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Faculty Seminar Series — March 31

Julie D. Tucker, Ph.D. Assistant Professor, Oregon State University
Role of Alloying on Phase Transformations in Ni-Cr Alloys

The development of long range ordered phases in Ni-Cr alloys can degrade material properties and is a potential concern for nuclear power systems. The ordering rate and the factors that influence it need to be better understood to predict behavior of Ni-Cr alloys during long term service at intermediate temperatures. In order to quantify the ordering kinetics, we apply a combined computational-experimental approach on model alloys, with Ni/Cr atomic ratios near 2:1. Isothermal agings were conducted at temperatures between 333°C–470°C for times up to 10,000 hours. The effects of alloying (0-9 wt.% Fe), cold work and excess vacancies were investigated and ordering was assessed by changes in the lattice parameter and hardness. Kinetic Monte Carlo simulations and experiments show that ordering is well described by Kolmogorov-Johnson-Mehl-Avrami kinetics. Solute-vacancy interactions of common alloying elements (Mo, Mn, Si, and Nb) were investigated via first-principles to better understand ordering in complex engineering alloys.

Biographical Information
Dr. 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 an emphasis in Materials Science in 2008. After graduation, Dr. Tucker spent five years as a Principal Scientist at Knolls Atomic Power Laboratory (KAPL) in Schenectady, NY studying the thermal stability of structural alloys for nuclear power systems. She recently joined the Mechanical, Industrial, and Manufacturing Engineering department at Oregon State University as an Assistant Professor. Her research efforts are focused on nuclear materials and metallurgy and leverage both modeling and experimental approaches to gain fundamental understanding of materials degradation mechanisms.


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