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Materials Science and Engineering Seminar
Dr. Joshua Mueller
Research and Development Engineer
Dynamic-Structure Design and Engineering Group, Los Alamos National Laboratory
Intercritical annealing (IA) of medium-Manganese (Mn) steels is a metallurgical design concept for the production of high-strength, formable sheet steel. The primary objective of the IA heat treatment is to partition solute Carbon (C) and Mn to intercritical austenite so that it may be retained to room temperature, resulting in a final microstructure of retained austenite and ferrite. The work presented elucidates ferrite-to-austenite phase transformation mechanisms during IA, and investigates the efficacy of generating Mn-enriched austenite during relatively short heat treatments. Aspects of the ferrite-to-austenite transformation associated with Mn-banded microstructures are also discussed, and linked to austenite evolution during double soaking treatments when austenite formation continues after IA at an elevated temperature. Scanning transmission electron microscopy with energy dispersive X-ray spectroscopy (STEM-EDS), transmission Kikuchi diffraction (TKD), and field-emission scanning electron microscopy (FESEM) were utilized for microstructural characterization, while in situ high-energy X-ray diffraction (HEXRD), and dilatometry were used for bulk material assessments. Phase field simulations using MICRESS® and one-dimensional diffusional simulations with the DICTRATM module of Thermo-Calc® will also be discussed.
Josh Mueller is a Research and Development Engineer in the Dynamic-Structure Design and Engineering Group at Los Alamos National Laboratory where he serves as the metallurgical technical lead. He holds a PhD from Colorado School of Mines in Metallurgical and Materials Engineering, and a BS in Materials Science and Engineering from the University of Wisconsin-Madison. His research interests include phase transformations and microstructural evolution associated with multi-phase microstructures, as well as microstructure-mechanical property relationships of metals. He is particularly interested in microstructural design to enhance yield strength-toughness combinations of ferrous alloys, and incorporating thermodynamic and phase field simulations for an integrated computational materials engineering (ICME) approach to alloy and heat treatment development.
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