Author ORCID Identifier
Year of Publication
Doctor of Philosophy (PhD)
Chemical and Materials Engineering
Experimental process simulation and quantification of microstructure development during processing are challenging due to limitations with machinery temperature capability, inadequate resolution and sampling volume of currently available characterization techniques, and difficulty characterizing material microstructures as close to processing-relevant conditions as possible. This dissertation addresses how process simulation can be performed using Gleeble thermomechanical technologies and how microstructure development during these processing simulations can be quantified both in-situ and ex-situ.
The first portion of this dissertation demonstrates how Gleeble technologies can be applied to simulate complex material processing conditions in order to produce process-property profiles that can be used to inform process-related decision making and improve product quality. Presented work details continuous casting simulations in a Gleeble 3500 that generate comprehensive ductility information throughout casting operations that can be utilized to avoid hot cracking phenomenon prevalent in high-strength low-alloy (HSLA) steel grades. Recreation of continuous casting processes in this dissertation provides a framework to demonstrate how complex casting and forming operations can be simulated and details how these techniques can be leveraged to identify major ductility limited zones and factors negatively impacting material ductility during casting. Fundamental mechanisms governing microstructure evolution that cause high-temperature low-ductility behavior in HSLA steels are also examined, where low-ductility behaviors are believed to emanate from precipitation and/or phase transformation effects during initial casting stages. This work uses novel techniques to examine precipitation and phase transformation evolution during continuous casting in order to identify the extent that these microstructure features influence ductility performance of cast steels.
The second portion of this dissertation examines current state-of-the-art characterization techniques in order to evaluate which techniques are suitable for quantification of nanoscale precipitation in steel and aluminum alloys. In this work, the merits and limitations of three techniques were evaluated: scanning transmission electron microscopy (STEM), small-angle x-ray scattering, and a new software analysis tool developed by ThermoFisher scientific: automated particle workflow (APW). This work compares capabilities of novel and well-established characterization methods to determine suitability for use in a range of applications where precipitate characterization is necessary. Improving characterization and quantification techniques for increasingly small length scales provides improved ability to understand fundamental material properties and microstructure formation that is relevant to refine process design for desired material outcomes.
Digital Object Identifier (DOI)
Stubbers, Alyssa, "Thermomechanical process simulation and quantification of nanoscale precipitation influencing ductility and strength during alloy processing" (2024). Theses and Dissertations--Chemical and Materials Engineering. 159.