2022 Technical Division Student Poster Contest: SMD 2022 Technical Division Graduate Student Poster Contest
Program Organizers: TMS Administration
Monday 5:30 PM
February 28, 2022
Room: Exhibit Hall C
Location: Anaheim Convention Center
SPG-33: Computational Modeling of Non-equilibrium Phenomena in Laser Additive Manufacturing Using Molecular Dynamics: Gurmeet Singh1; Veera Sundararaghavan1; 1University of Michigan
Additive manufacturing of a single crystalline metallic column is studied using molecular dynamics simulations. In the model, a melt pool is incrementally added and cooled to a target temperature under isobaric conditions to build a metallic column. We investigated the microstructure evolution of the solidified column and looked at the influence of cooling rate, powder bed temperature, and effect of added inclusion on the defects. The new additions to the code are the use of tight-binding DFT potentials to model multi-component alloy systems and the use of this approach to improve the modeling of laser-atom interactions. Current laser-matter interaction models use two-temperature classical potentials that do not capture the electronic effects accurately. With DFT tight binding dynamics, we study how the laser interacts with various atom types in higher detail. We study the role that inclusions play in reducing or worsening the retained defects in the additive column.
SPG-34: Development of a Generalized Fatigue Assessment Approach for Steel Castings: Bret Cordle1; James Jordon1; Paul Allison1; Hayley Brown2; Jacob Williamson1; 1The University of Alabama; 2Steel Founders Society of America
In this work, a generalized model for steel castings is employed to capture the effects steel casting features (i.e. shrinkage porosity, gas pores) on the fatigue performance. It has been well documented that the soundness of the casting has drastic effects on the fatigue performance, however there is still a modern day need to present a quantified assessment of process-structure-property performance that incorporates common non-destructive analysis techniques to estimate the fatigue life properties of the component. The proposed model elucidates constitutive fatigue behavior and has been created from strain-life fatigue behavior, microstructural properties, and post-mortem fractography for cast 4130 steel. The model was validated across literature data concerning the fatigue life of other cast steels to show the applicability of the new model across the industry. Further, the model presented has been shown to provide fatigue life predictions of cast steels to an acceptable degree of engineering accuracy.
SPG-35: Discovering the Corrosion Mechanism of Chromium in High-temperature LiF-NaF-KF Molten Salts for Gen-IV Molten Salt Reactor Applications: Ho Lun Chan1; Elena Romanovskaia1; Minsung Hong2; Peter Hosemann2; John Scully1; 1University of Virginia; 2University of California Berkeley
Chromium, a ubiquitous and powerful alloying element possible structural materials in advanced nuclear reactor alloys, is susceptible to selective dissolution in molten fluoride salts in the presence of hydrofluoric acid, which is formed by the adsorption and reaction of moisture impurity in molten fluorides. In this project, the thermodynamic stability of Cr in the Cr0, Cr2+ and Cr3+ oxidation states considering various F- ion coordination was investigated in molten LiF-NaF-KF (FLiNaK) eutectic salt. Corrosion was a strong function of thermodynamic and kinetic factors. Potential-fluoride ion activity diagrams were constructed to predict the F- stability region where spontaneous corrosion of Cr occurs. Electrochemical methods were utilized to relate the interface corrosion kinetics to the predicted stability region. The present work aims to identify key thermodynamic and kinetic factors that are significant to the chromium corrosion for molten salt nuclear reactor applications.
SPG-36: Effect of Oxide Impurities on Corrosion of Materials in Molten Fluoride Salt: Krishna Moorthi Sankar1; Preet Singh1; 1Georgia Institute of Technology
One of the major issues in the design of MSRs is the significant corrosion of structural materials in FLiNaK. The corrosion in the form of selective dissolution of alloying elements in these molten salts depends on their redox potential, which in-turn depends on the type and amount of impurities present. There have been very few studies on the effect of oxide impurities, that may come with the salt or from the passive films formed on alloy surfaces, on this corrosion. In this study, corrosion behavior of selected Ni and Fe based alloys were studied in molten FLiNaK salt at 700 °C. Various oxide impurities such as Li2O, NiO, and Cr2O3 were added to baseline FLiNaK to understand their effect on this corrosion. This presentation will discuss our results on the effect of oxide impurities on the mode and extent of corrosion of candidate alloys in FLiNaK.
SPG-39: Mechanical Behavior of a Next-generation Steel (AF9628) Printed via Directed Energy Deposition: Ankita Roy1; Ravi Haridas1; Rajiv Mishra1; B McWilliams1; Clara Mock1; K Cho1; 1University of North Texas
Compared to conventional material processing techniques, wider solidification range of additive manufacturing (AM) provides opportunity to tailor heterogenous and hierarchical microstructures. Multiple AM systems are being simultaneously adopted by industry to leverage unique process dynamics associated with each AM technique. The relatively slower solidification kinetics associated with directed energy deposition (DED) has been found to improve strength-ductility synergy for a new class of high-strength low alloy steel (AF9628). DED method using high melt pool overlap rate provides an excellent medley of auto-tempering of the martensitic laths and optimizing volume fraction of carbides that results in the observed mechanical behavior. Our analyses involve venturing into the holistic influences of prior austenite grain size, solidification morphology, elemental segregation along cell boundaries and also exposing the role of carbides in shaping the mechanical properties of the alloy.