Metallurgy Commons^™

Inclusion Engineering Through Deoxidation Practice Optimization For Enhanced Mechanical Properties Of Cast Cr-Ni-Mo Steel, Kingsley T. Amatanweze, Viraj A. Athavale, Simon Lekakh, Ronald J. O'Malley, Laura N. Bartlett

Materials Science and Engineering Faculty Research & Creative Works

Deoxidation is an integral part of steelmaking, as it determines steel castability, cleanliness, and porosity levels of the final product. Steel quality is critical to its performance and can be sabotaged by impurities such as non-metallic inclusions and porosity. This study investigates the effects of four distinct deoxidation practices, using Al, Al-Ca, Zr-Ca, and Mn-Si respectively, on tensile strength, tensile ductility and impact toughness of a Cr-Ni-Mo steel. These deoxidation reactions were modeled on a commercially available thermodynamic software and possible inclusion product phases were predicted. The casting samples were studied on a scanning electron microscope (SEM) utilizing energy dispersive …

Post-Calcium Treatment Evolution Of Alumina (Al2o3) Inclusions Morphology, Naziru I. Fuseini, Ronald J. O'Malley, Todd P. Sander, Jeffrey D. Smith, Haiming Wen, Laura N. Bartlett

Materials Science and Engineering Faculty Research & Creative Works

The post-calcium morphological evolution of Al₂O₃ inclusions formed under high-oxygen supersaturation (~1000 ppm) was investigated through time-resolved sampling and quenching of aluminum-killed, calcium-treated steel. SEM-EDS analysis revealed the formation of angular two-phase CaO·Al₂O₃–CaS inclusions within 1 minute, gradually transforming into spherical liquid 12CaO·7Al₂O₃ and CaO·Al₂O₃ with a thin CaS layer around it. The 3D morphology of the CaS phase of the complex CaO·Al₂O₃–CaS inclusions observed at 1 minute appeared as a cone-cap attached to the partially modified CaO·Al₂O₃. This …

Examination Of Laser Microwelding As A Technique For The Repair Of Steel Castings, Allan John Woldow

Masters Theses

"Metal castings have long been plagued with minor defects caused by various process and design conditions. Commonly, minor defects are not seen until after machining operations have been completed, and by the time they are identified, they cannot be salvaged in a manner that is structurally sound and does not have other detrimental effects on the product. Detrimental effects may include warping from high heat input in traditional welding, warping from reheat treatment, oxidation of machined surfaces, microstructural anomalies, and reduced mechanical properties. Micro laser welding has the potential to provide a solution to these issues by providing a low …

Castrip Process Technology: Non-Grain Oriented (Ngo) Si Steels Extension And Carbide-Free Bainitic (Cfb) For Flat Products, Naram Naidu Meesala

Masters Theses

"This research explores the development of advanced steel grades manufactured through Castrip® twin-roll thin strip casting technology, with particular attention to non-grain-oriented electrical Si-Steels (NGOES) and carbide-free bainitic (CFB) steels. The Castrip® process offers a near-net-shape route for producing thin steel strips, which greatly decreases the number of processing stages, lowers energy demand, and reduces carbon dioxide emissions when compared with traditional steel production methods.

In the NGOES part of the study, several industrial Fe–Si steel compositions were cold rolled to final thicknesses ranging from 0.35 mm to 0.15 mm. These materials were then exposed to short-duration continuous annealing at …

Critical Parameters Controlling Oxide Scale Formation And Hydro-Descaling Efficiency During Steelmaking, Tochukwu Princewill Ojiako

Doctoral Dissertations

In modern steelmaking, cast slabs are exposed to high-temperature oxidizing environments during secondary cooling, reheating, and hot rolling, resulting in the formation of multilayer oxide scales on the steel surface. These scales interact with mold-flux residues originating from the casting process (CC). The morphology, chemistry, and adhesion of oxide scale strongly influence its removability during high-pressure hydraulic descaling and ultimately determine the surface quality of hot-rolled products. However, the mechanistic relationship between oxide scale evolution, scale-steel interfacial structure, and hydraulic descaling performance remains poorly understood.

This dissertation investigates oxide scale formation, modification, and removal in low-carbon thin-slab steels produced by …

Electron Beam Irradiation Effects On Bulk Metals: A Comparative Study Of Polycrystalline Versus Single-Crystalline Structures, A. A. Elmustafa, N. A. Sultana, A. H. Al-Allaq, M. Ojha, Y. S. Mohammed, J. Vennekate, H. Baumgart

Mechanical & Aerospace Engineering Faculty Publications

This study investigates the effects of electron beam (e-beam) irradiation on the mechanical and structural properties of eight bulk metallic samples, comprising both polycrystalline (PC) and single-crystalline (SC) forms of Ni, Cr, V, and Ti. These metals were evaluated as potential candidates for beam exit windows in high-power (MW-class) particle accelerators. The primary objective is to identify metals capable of withstanding the conditions of high-power/MW-class e-beam accelerators and serve effectively as exit windows. Selection criteria were based on each metal’s intrinsic properties, power dissipation capability, and irradiation-induced changes in mechanical behavior, including hardness, elastic modulus, and defect density. Comprehensive characterization …

Multidentate Surfactant-Dependent Synthesis Of Giant Iridium Superstructures, Ramjee Balasubramanian, Maeren E. Hill

Chemistry & Biochemistry Faculty Publications

Giant superstructures of iridium, comprised of smaller spherical and slightly larger anisotropic nanoparticles, were synthesized by reducing iridium chloride in the presence of resorcinarene, a class of tetrameric macrocyclic polyphenols, with sodium borohydride in ethanol in 30 min under mild conditions. These superstructures were characterized by a range of techniques including TEM, HRTEM, EDS and other spectroscopic methods. The impact of the macrocyclic surfactant, its features and reaction conditions in dictating the formation of giant iridium superstructures was evaluated. The packing density of nanoparticles in these giant iridium superstructures could be altered qualitatively by varying the duration of the reaction, …

Multiphysics Modeling Of Melt Pool Dynamics And Powder Bed Stability In Lpbf Of Inconel 718 For A Circular Cavity, Nayan Pundhir, Oluwapelumi O. Adejumo, Kumbla Chandrashekhara, Joseph W. Newkirk, Heath Misak, Cesar Ortiz Rios

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Laser powder bed fusion (LPBF) is a metal additive manufacturing process in which a concentrated laser beam selectively melts successive powder layers to fabricate components. Final part quality is highly sensitive to process parameters such as hatch spacing, powder bed density, laser power, and scanning speed. In this study, a computational fluid dynamics model employing discrete element method has been developed in FLOW-3D to simulate LPBF of Inconel 718. The modeled powder bed incorporates particle size distribution data obtained from scanning electron microscopy and is evaluated for single-layer, single-track deposition over a circular cavity. The model captured melt pool dynamics …

Development Of Stronger, More Extrudable 6xxx Series Alloys For Automotive Applications, Eli A. Harma

Dissertations, Master's Theses and Master's Reports

6xxx alloys are widely used in automotive extrusion structures for their high specific strength and formability. Advanced designs require greater formability and strength, creating an opportunity for high-strength, formable alloys. The 6xxx series forms β”-Mg₅Si₆ precipitates during age hardening and develops a fibrous microstructure during extrusion, both strengthening the alloy. Increasing Mg and Si to form more β” decreases formability. Thus, modifying texture can increase strength without reducing formability. Current alloys like 6005A add Mn and Cr to form dispersoids that inhibit recrystallization and promote strengthening textures; however, high Mn and Cr concentrations reduce formability. Replacing Mn …

Methodology Development For Evaluating Relative Heat Checking Resistance Of Open-Die Forge Tooling, Jack F. Schaller

Dissertations, Master's Theses and Master's Reports

Heat checking, characterized by biaxial networks of surface cracks induced by thermomechanical cycling, can cause premature failure of open-die forge tooling. To facilitate the evaluation of heat checking resistance of die steels, a simulation‑informed out-of-phase thermomechanical fatigue (OP-TMF) testing methodology was developed using 4330V steel as a baseline material. Temperature‑dependent material properties and flow stress data were collected and compiled into a material data file for use with finite element analysis software. Forging and cooling scenarios were simulated across a range of die preheat temperatures. Temperature and in-plane strain histories extracted from the die surface provided a foundation for laboratory …

Feasibility Of Upcycling Spent Lithium-Ion Battery To Carbon Dioxide Capture Adsorbent, Chimezie Frank Onwudinjo

Master’s Theses

This study investigates the feasibility of repurposing spent lithium-ion battery (SLIB) to lithium orthosilicate (Li₄SiO₄), a high temperature carbon dioxide sorbent. Two synthesis pathways including conventional acid-leaching method (Scenario 1) and a pyrolysis-based route (Scenario 2) were explored. Additionally, techno-economic analysis (TEA) and lifecycle assessment (LCA) of the two processes were also performed. Different analytical characterization techniques were performed to understand the material properties of Li₄SiO₄ including surface area, crystallinity, morphology and thermal stability. CO₂ capture performance of the synthesized Li₄SiO₄ was tested in a thermogravimetric analyzer (TGA) using …

Breaking The Vapor Barrier And Scale: Revolutionizing Steel Quenching With Ultrasound Technology, Anthony O. Santos

Williams Honors College, Honors Research Projects

The quenching process is a fundamental heat treatment used to enhance material properties by heating steel to its austenitizing temperature and rapidly cooling it to form high-strength martensite. However, this process is often hindered by two surface barriers: the Leidenfrost effect (vapor blanket) and oxide scale. These cooling limitations restrict the use of steel in high-performance aerospace applications due to inconsistent material properties and unpredictable engineering properties. This research investigates the use of fully submersible, 50-watt 40 kHz ultrasound technology to improve cooling rates in a Jominy test [4]. Through numerical simulations and experimental validation, the study demonstrates that acoustic …

Optimization Of Post-Processing Methods For Additively Manufactured Metals, Julia R. Carano

Williams Honors College, Honors Research Projects

Ultrasonic Nanocrystal Surface Modification (UNSM) is a process used to change the surface hardness of flat-faced materials. It is a machining process using a high-powered laser and a blunt-tipped tool at high speeds which aims to improve the uniformity of the surface on most metals. By heating and pressing the surface of the workpiece, the grains of the material become less rounded and more cohesive on a microscopic level. This, ideally, results in a workpiece with improved material properties. The changes were previously observed through hardness testing.

Fused Filament Fabrication Additive Manufacturing Of 17-4 Ph Stainless Steel: Process–Structure–Property Relationships In Magnetic Materials, Maanav Patel

Theses and Dissertations

Additive manufacturing (AM) enables the fabrication of complex metallic components through layer-by-layer processing directly from digital models. Among AM techniques, material extrusion–based processes such as fused filament fabrication (FFF) provide an accessible method for producing metal parts using filament feedstocks composed of metal powders and polymer binders. When applied to precipitation-hardening stainless steels such as 17-4 PH, the processing route and heat treatments can influence the resulting microstructure and functional properties. This work investigates the magnetic behavior of 17-4 PH stainless steel fabricated using FFF and evaluates how heat treatment conditions influence measured magnetic properties. Samples were produced and analyzed …

Ion-Imprinted Polymer-Based Sensors For Toxic Metal-Ion Detection In Water: Coordination Chemistry, Transduction Strategies, And Environmental Applications, Ghita Yammouri, Gymama Slaughter

Center for Bioelectronics Publications

Toxic metal contamination in aquatic environments remains a persistent threat to human health and ecosystems. Yet, the high cost, infrastructure demands, and centralized nature of conventional analytical methods constrain routine monitoring. Ion-imprinted polymers (IIPs), a subclass of molecularly imprinted polymers, have emerged as promising synthetic recognition materials for metal-ion sensing because they generate coordination-defined binding sites with high selectivity, chemical stability, low cost, and reusability. This review summarizes recent advances in Ion-imprinted polymer (IIP)-based sensing technologies for toxic metal-ion detection in water from 2016 to 2026. It examines the fundamental recognition chemistry of IIPs, major synthesis strategies used to generate …

Nanostructured Cathode Catalysts For Aem Electrolysis: From Catalyst Design To Degradation And Hydrogen Dynamics, Yamini Kumaran

Electronic Theses & Dissertations (2024 - present)

Anion exchange membrane water electrolysis (AEMWE) presents a promising pathway toward cost-effective and sustainable hydrogen production by integrating the chemical robustness of alkaline systems with the compact, zero-gap design of proton exchange membrane electrolyzers. However, the widespread implementation of AEMWE is limited by the availability of highly active and durable platinum-group-metal (PGM)-free catalysts and by an incomplete understanding of their degradation behavior under realistic operating conditions.

This dissertation focuses on the development, characterization, and mechanistic investigation of nanostructured MoNi₄–MoO₂-based electrodes for efficient and stable hydrogen generation under alkaline and membrane-integrated environments. MoNi₄–MoO₂ nanorods …

Investigation Of Fine-Grain Cu And Cu Alloys For Low-Temperature Hybrid Bonding Applications, Sarabjot Singh

Electronic Theses & Dissertations (2024 - present)

Hybrid bonding has emerged as a key enabler for next-generation three-dimensional (3D) integration, offering fine-pitch interconnects and improved electrical performance. However, conventional Cu–Cu hybrid bonding typically requires elevated temperatures to achieve sufficient diffusion and interface quality, posing challenges for temperature-sensitive device integration and process compatibility. This work investigates materials engineering approaches to enable low-temperature Cu–Cu bonding through both microstructure design and alloying strategies.

This work begins by examining grain refinement in Cu as a pathway to enhance diffusion through increased grain boundary density, providing efficient atomic transport without introducing additional elements. Three Cu-based systems Cu–Co, Cu–Ag, and Cu–Al were systematically …

High Temperature Creep Deformation Mechanism Of Fe28.2ni18.8mn32.9al14.1cr6 High Entropy Alloy And Its Modified Alloys, Edwin S. Jiang, I. Baker

Dartmouth College Ph.D Dissertations

Fe28.2Ni18.8Mn32.9Al14.1Cr6 eutectic high entropy alloy exhibits a good combination of room-temperature and high temperature properties, including tensile strength, ductility, and corrosion resistance, making it a promising candidate for structural applications in extreme environments. However, the creep deformation behavior of this alloy— and high-entropy alloys (HEAs) in general—remains insufficiently understood. This dissertation systematically investigates the high-temperature creep deformation mechanisms of Fe28.2Ni18.8Mn32.9Al14.1Cr6 and its derivatives.

Creep mechanisms and associated microstructural changes were examined across a wide range of strain rates using strain-rate jump and constant-stress tests. Two dominant regimes were identified: dislocation glide/solute-drag at low strain rates, and dislocation climb at high …

Effects Of Composition, Nodularity, Pouring Temperature, Inoculation, And Mold Strength On Wall-Movement In Sgi Castings During Solidification And Cooling, Noah Brack

College of Graduate Studies: Theses & Dissertations

The iron-carbon casting alloy known as spheroidal graphite iron (SGI), nodular graphite iron, or ductile iron (DI) experiences complex volume changes during its solidification and cooling as graphite nodules and austenite form. These volume changes result in forces on the mold cavity walls and can deform the mold walls in cases when mold walls lack the strength to resist the deformation. This wall movement can cause the formation of casting defects such as swell, warped part geometry, and shrinkage porosity. Though this phenomenon has been studied in the past, it remains difficult to predict casting wall movement with existing data. …

Effect Of Wall Movement On Porosity Formation In Ductile Iron Castings Under Varying Processing Parameters, Shamsul Alam

College of Graduate Studies: Theses & Dissertations

Shrinkage porosity is a major defect that significantly impairs the mechanical properties and overall performance of ductile iron castings. Although graphite formation during solidification induces volumetric expansion, this expansion alone is insufficient to fully compensate for the shrinkage occurring throughout solidification. During the solidification and cooling of ductile iron, multiple phase transformations occur, resulting in dynamic volume changes that exert pressure on mold walls and internal cavities. These pressures can deform mold walls and casting surfaces, leading to defects such as swell and porosity, while also influencing shrinkage formation. This study aims to analyze the mechanisms of porosity formation and …