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Control Of Columnar To Equiaxed Transition In Solidification Macrostructure Of Austenitic Stainless Steel Castings, Semen Naumovich Lekakh, Ronald J. O'Malley, Mark Emmendorfer, Brenton Hrebec 2017 Missouri University of Science and Technology

Control Of Columnar To Equiaxed Transition In Solidification Macrostructure Of Austenitic Stainless Steel Castings, Semen Naumovich Lekakh, Ronald J. O'Malley, Mark Emmendorfer, Brenton Hrebec

Ronald J. O'Malley

Solidification macrostructure is of great importance for the properties and the quality of castings made from austenitic grade stainless steels (ASS) because there are limited options to change as-cast macrostructure in the solid condition. A typical cast macrostructure of ASS has a fine surface chilled zone followed by an elongated dendrite zone, columnar to equiaxed transition (CET) zone, and centrally located equiaxed crystals. Several castings from ASS were produced to determine the effects of casting geometry, chilling, and grain refinement on CET. The transient thermal field in solidified heavy castings was simulated and used to determine an isotherm velocity (V ...


Evolution Of Non-Metallic Inclusions In Foundry Steel Casting Processes, Marc Harris, Von Richards, Ronald J. O'Malley, Semen Naumovich Lekakh 2017 Missouri University of Science and Technology

Evolution Of Non-Metallic Inclusions In Foundry Steel Casting Processes, Marc Harris, Von Richards, Ronald J. O'Malley, Semen Naumovich Lekakh

Ronald J. O'Malley

The evolution of nonmetallic inclusions was examined for 4320 steel at an industrial steel foundry. The steel was followed from electric arc furnace melting through ladle refining to final casting. Timed sampling was performed at all stages of the process. Samples were analyzed using an automated SEM/EDS system. The overall evolution of oxide inclusions in terms of nucleation, growth, and flotation during liquid processing was studied using area fraction and average diameter. Chemical composition evolution was observed using a joint ternary plotting tool developed under this program. It was found that the use of zirconium as an addition for ...


Effect Of Zinc Galvanization On The Microstructure And Fracture Behavior Of Low And Medium Carbon Structural Steels, Ignatius C. Okafor, Ronald J. O'Malley, Kaushal R. Prayakarao, Heshmat A. Aglan 2017 Missouri University of Science and Technology

Effect Of Zinc Galvanization On The Microstructure And Fracture Behavior Of Low And Medium Carbon Structural Steels, Ignatius C. Okafor, Ronald J. O'Malley, Kaushal R. Prayakarao, Heshmat A. Aglan

Ronald J. O'Malley

Microstructure and fracture behavior of ASTM 572 Grade 65 steels used for wind tower applications have been studied. Steels of two carbon level chemistries designed for this grade were used in the study. Fracture toughness of the steels was studied using 3-point bend test on samples coated with zinc and not coated with zinc. Lower carbon steel showed higher resistance to fracture than medium carbon steel after zinc galvanization. SEM study suggests that zinc and zinc bath additives that migrated to crack tips are responsible for the loss in ductility. The phenomenon of Liquid Metal Embrittlement (LME) is suggested to ...


Gamma-Radiation Induced Corrosion Of Alloy 800, Mojtaba Momeni 2017 The University of Western Ontario

Gamma-Radiation Induced Corrosion Of Alloy 800, Mojtaba Momeni

Electronic Thesis and Dissertation Repository

This thesis presents a newly developed mechanism and predictive model for the corrosion of Alloy 800. The Fe-Cr-Ni Alloy (Incoloy 800) is mainly used for steam generator (SG) tubing in CANDU and PWR reactors and is a candidate material for the proposed Canadian Supercritical Water Reactor (SCWR) in which it will be exposed to extreme conditions of high radiation flux and large temperature gradients. The influence of gamma radiation and water chemistry conditions on the corrosion behaviour of Alloy 800 are studied in this work. Ionizing radiation creates reducing (•eaq, •H, •O2-) and oxidizing radiolysis (•OH, H2 ...


Analysis Of Variable Insensitive Friction Stir Welding Parameters, Robert L. Marrero Jr 2017 University of New Orleans

Analysis Of Variable Insensitive Friction Stir Welding Parameters, Robert L. Marrero Jr

University of New Orleans Theses and Dissertations

Friction Stir Welding (FSW) was used to perform a Design of Experiment (DOE) to determine the welding parameters effects on yielding consistent mechanical properties across the length of the weld. The travel speed was varied across set forge force and RPM conditions, to find a dataset that will yield consistent mechanical properties independent of the travel speed. Six different welds were completed on two different aluminum panels, the advancing side being Aluminum alloy 2195-T8 at a thickness of .350”, with the retreating side being Aluminum alloy 2219-T851 with a gauge thickness of .360”. A Left-hand Right-hand self-reacting pin tool was ...


Irradiation-Induced Nanocluster Evolution, Didier Ishimwe, Matthew J. Swenson, Janelle P. Wharry 2017 William Penn University

Irradiation-Induced Nanocluster Evolution, Didier Ishimwe, Matthew J. Swenson, Janelle P. Wharry

The Summer Undergraduate Research Fellowship (SURF) Symposium

Oxide dispersion strengthened steel (ODS) and commercial ferritic-martensitic (F-M) alloys are widely accepted candidate structural materials for designing advanced nuclear reactors. Nanoclusters embedded in the steel matrix are key microstructural features of both alloy types. Irradiation from nuclear fusion and fission affects the morphology of these nanoparticles, altering the performance of the alloys and potentially decreasing their usable lifetime. Thus, it is important to understand the effect of irradiation on these nanoparticles in order to predict long-term nuclear reactor performance. It was found that the evolution of nanoclusters in each material is different depending on the experimental irradiation parameters. The ...


The Mechanism Of Radiation-Induced Nanocluster Evolution In Oxide Dispersion Strengthened And Ferritic-Martensitic Alloys, Matthew John Swenson 2017 Boise State University

The Mechanism Of Radiation-Induced Nanocluster Evolution In Oxide Dispersion Strengthened And Ferritic-Martensitic Alloys, Matthew John Swenson

Boise State University Theses and Dissertations

The objective of this study is to evaluate the mechanism of irradiation-induced nanoparticle evolution in a model Fe-9%Cr oxide dispersion strengthened steel and commercial ferritic-martensitic alloys HCM12A and HT9. Each alloy is irradiated with Fe2+ ions, protons, or neutrons to doses ranging from 1-100 displacements per atoms at 500°C. The morphology of nanoclusters are characterized using atom probe tomography. The evolution of clusters in each alloy are notably different with each irradiating particle, and the competing effects of ballistic dissolution and radiation-enhanced, diffusion-driven growth are attributed to the respective differences in cluster evolution. A phase evolution model ...


Engineered, Spatially Varying Isothermal Holds: Enabling Combinatorial Studies Of Temperature Effects, As Applied To Metastable Titanium Alloy Β-21s, Brian Martin, Peyman Samimi, Peter C. Collins 2017 Iowa State University

Engineered, Spatially Varying Isothermal Holds: Enabling Combinatorial Studies Of Temperature Effects, As Applied To Metastable Titanium Alloy Β-21s, Brian Martin, Peyman Samimi, Peter C. Collins

Peter Collins

A novel method to systematically vary temperature and thus study the resulting microstructure of a material is presented. This new method has the potential to be used in a combinatorial fashion, allowing the rapid study of thermal holds on microstructures to be conducted. This is demonstrated on a beta titanium alloy, where the thermal history has a strong effect on microstructure. It is informed by simulation and executed using the resistive heating capabilities of a Gleeble 3800 thermomechanical simulator. Spatially varying isothermal holds of 4 h were affected, where the temperature range of the multiple isothermal holds varied by ~175 ...


Comparative Study Of The Tribological And Oxidative Properties Of Alpdmn Quasicrystals And Their Cubic Approximants, Chris Mancinelli, Jeff S. Ko, Cynthia J. Jenks, Patricia A. Thiel, Amy R. Ross, Thomas A. Lograsso, Andrew J. Gellman 2017 Carnegie Mellon University

Comparative Study Of The Tribological And Oxidative Properties Of Alpdmn Quasicrystals And Their Cubic Approximants, Chris Mancinelli, Jeff S. Ko, Cynthia J. Jenks, Patricia A. Thiel, Amy R. Ross, Thomas A. Lograsso, Andrew J. Gellman

Thomas A. Lograsso

An experimental comparison has been made between the properties of the surfaces of an Al70Pd21Mn9quasicrystal and its Al48Pd42Mn10 approximant. The Al70Pd21Mn9 sample was a single grain icosahedral quasicrystal cut to expose its five-fold symmetric (000001) surface. The approximant was polycrystalline β-phase Al48Pd42Mn10, which has a CsCl-type cubic structure. Surfaces of both were prepared under ultra-high vacuum (UHV) conditions and then used for comparative measurements of their frictional properties and oxidation rates. Both materials are oxidized by reaction with O ...


Rhombohedral Magnetostriction In Dilute Iron (Co) Alloys, Nicholas J. Jones, Gabriela Petculescu, Marilyn Wun-Fogle, James B. Restorff, Arthur E. Clark, Kristi B. Hathaway, Deborah L. Schlagel, Thomas A. Lograsso 2017 Naval Surface Warfare Center

Rhombohedral Magnetostriction In Dilute Iron (Co) Alloys, Nicholas J. Jones, Gabriela Petculescu, Marilyn Wun-Fogle, James B. Restorff, Arthur E. Clark, Kristi B. Hathaway, Deborah L. Schlagel, Thomas A. Lograsso

Thomas A. Lograsso

Iron is a well-utilized material in structural and magnetic applications. This does not mean, however, that it is well understood, especially in the field of magnetostriction. In particular, the rhombohedral magnetostriction of iron, λ111 , is anomalous in two respects: it is negative in sign, in disagreement with the prediction of first principles theory, and its magnitude decreases with increasing temperature much too rapidly to be explained by a power law dependence on magnetization. These behaviors could arise from the location of the Fermi level, which leaves a small region of the majority 3d t2g states unfilled, possibly favoring small internal ...


Magnetic Excitations And Anomalous Spin-Wave Broadening In Multiferroic Fev2o4, Qiang Zhang, Mehmet Ramazanoglu, Songxue Chi, Yong Liu, Thomas A. Lograsso, David Vaknin 2017 Iowa State University

Magnetic Excitations And Anomalous Spin-Wave Broadening In Multiferroic Fev2o4, Qiang Zhang, Mehmet Ramazanoglu, Songxue Chi, Yong Liu, Thomas A. Lograsso, David Vaknin

Thomas A. Lograsso

We report on the different roles of two orbital-active Fe2+ at the A site and V3+ at the B site in the magnetic excitations and on the anomalous spin-wave broadening in FeV2O4. FeV2O4 exhibits three structural transitions and successive paramagnetic (PM)–collinear ferrimagnetic (CFI)–noncollinear ferrimagnetic (NCFI)/ferroelectric transitions. The high-temperature tetragonal/PM–orthorhombic/CFI transition is accompanied by the appearance of a large energy gap in the magnetic excitations due to strong spin-orbit-coupling-induced anisotropy at the Fe2+ site. While there is no measurable increase in the energy gap from the orbital ordering of V3+ at the orthorhombic/CFI–tetragonal ...


Second Order Phase Transition Temperature Of Single Crystals Of Gd5si1.3ge2.7 And Gd5si1.4ge2.6, Ravi L. Hadimani, Yevgen Melikhov, Deborah L. Schlagel, Thomas A. Lograsso, Kevin W. Dennis, R. William McCallum, David C. Jiles 2017 Iowa State University

Second Order Phase Transition Temperature Of Single Crystals Of Gd5si1.3ge2.7 And Gd5si1.4ge2.6, Ravi L. Hadimani, Yevgen Melikhov, Deborah L. Schlagel, Thomas A. Lograsso, Kevin W. Dennis, R. William Mccallum, David C. Jiles

Thomas A. Lograsso

Gd5(Six Ge 1−x)4 has mixed phases in the composition range 0.32 < x < 0.41, which have not been widely studied. In this paper, we have synthesized and indexed single crystal samples of Gd5Si1.3 Ge 2.7 and Gd5Si1.4 Ge 2.6. We have investigated the first order and second orderphase transition temperatures of these samples using magnetic moment vs. temperature andmagnetic moment vs. magnetic field at different temperatures. We have used a modified Arrott plot technique that was developed and reported by us previously to determine the “hidden” second order phase transition temperature of the orthorhombic II phase.


Gd5(Si,Ge)4 Thin Film Displaying Large Magnetocaloric And Strain Effects Due To Magnetostructural Transition, Ravi L. Hadimani, Joao H. B. Silva, Andre M. Pereira, Devo L. Schlagel, Thomas A. Lograsso, Yang Ren, David C. Jiles, Joao P. Araújo 2017 Iowa State University

Gd5(Si,Ge)4 Thin Film Displaying Large Magnetocaloric And Strain Effects Due To Magnetostructural Transition, Ravi L. Hadimani, Joao H. B. Silva, Andre M. Pereira, Devo L. Schlagel, Thomas A. Lograsso, Yang Ren, David C. Jiles, Joao P. Araújo

Thomas A. Lograsso

Magnetic refrigeration based on the magnetocaloric effect is one of the best alternatives to compete with vapor-compression technology. Despite being already in its technology transfer stage, there is still room for optimization, namely, on the magnetic responses of the magnetocaloric material. In parallel, the demand for different magnetostrictive materials has been greatly enhanced due to the wide and innovative range of technologies that emerged in the last years (from structural evaluation to straintronics fields). In particular, the Gd5(Six Ge1−x)4 compounds are a family of well-known alloys that present both giant magnetocaloric and colossal magnetostriction effects. Despite their ...


Imprinting Bulk Amorphous Alloy At Room Temperature, Song-Yi Kim, Eun-Soo Park, Ryan T. Ott, T. A. Lograsso, Moo-young Huh, Do-Hyang Kim, Jürgen Eckert, Min-Ha Lee 2017 Korea Institute of Industrial Technology

Imprinting Bulk Amorphous Alloy At Room Temperature, Song-Yi Kim, Eun-Soo Park, Ryan T. Ott, T. A. Lograsso, Moo-Young Huh, Do-Hyang Kim, Jürgen Eckert, Min-Ha Lee

Thomas A. Lograsso

We present investigations on the plastic deformation behavior of a brittle bulk amorphous alloy by simple uniaxial compressive loading at room temperature. A patterning is possible by cold-plastic forming of the typically brittle Hf-based bulk amorphous alloy through controlling homogenous flow without the need for thermal energy or shaping at elevated temperatures. The experimental evidence suggests that there is an inconsistency between macroscopic plasticity and deformability of an amorphous alloy. Moreover, imprinting of specific geometrical features on Cu foil and Zr-based metallic glass is represented by using the patterned bulk amorphous alloy as a die. These results demonstrate the ability ...


Elastic Properties Of Mnsi, Fesi And Cosi, Alla E. Petrova, Vladimir N. Krasnorussky, William M. Yuhasz, Thomas A. Lograsso, Sergei M. Stishov 2017 Russian Academy of Sciences

Elastic Properties Of Mnsi, Fesi And Cosi, Alla E. Petrova, Vladimir N. Krasnorussky, William M. Yuhasz, Thomas A. Lograsso, Sergei M. Stishov

Thomas A. Lograsso

Measurements of sound velocities in single crystals of MnSi, FeSi, and CoSi were performed in the temperature range 2.5-300 K and elastic constants were calculated. The temperature dependence of the elastic constants reveal nontrivial features, reflecting specifics of the magnetic and electronic subsystems in these materials.


Effects Of Zn Additions To Highly Magnetoelastic Fega Alloys, Thomas A. Lograsso, Nicholas J. Jones, Deborah L. Schlagel, Gabriela Petculescu, Marilyn Wun-Fogle, James B. Restorff, Arthur E. Clark, Kristi B. Hathaway 2017 Iowa State University

Effects Of Zn Additions To Highly Magnetoelastic Fega Alloys, Thomas A. Lograsso, Nicholas J. Jones, Deborah L. Schlagel, Gabriela Petculescu, Marilyn Wun-Fogle, James B. Restorff, Arthur E. Clark, Kristi B. Hathaway

Thomas A. Lograsso

Fe1−xMx (M = Ga, Ge, Si, Al, Mo and x ∼ 0.18) alloys offer an extraordinary combination ofmagnetoelasticity and mechanical properties. They are rare-earth-free, can be processed using conventional deformation techniques, have high magnetic permeability, low hysteresis, and low magnetic saturation fields, making them attractive for device applications such as actuators and energy harvesters. Starting with Fe-Ga as a reference and using a rigid-band-filling argument, Zhang et al. predicted that lowering the Fermi level by reducing the total number of electrons could enhance magnetoelasticity. To provide a direct experimental validation for Zhang's hypothesis, elemental additions with lower-than-Ga valence are ...


Specific Heat Investigation For Line Nodes In Heavily Overdoped Ba1−Xkxfe2as2, J. S. Kim, G. R. Stewart, Yong Liu, Thomas A. Lograsso 2017 University of Florida

Specific Heat Investigation For Line Nodes In Heavily Overdoped Ba1−Xkxfe2as2, J. S. Kim, G. R. Stewart, Yong Liu, Thomas A. Lograsso

Thomas A. Lograsso

Previous research has found that the pairing symmetry in the iron-based superconductor Ba1−xKxFe2As2 changes from nodeless s wave near optimally doped, x≈0.4−0.55 and Tc>30K, to nodal (either d wave or s wave) at the pure end point, x=1 and Tc<4K. Intense theoretical interest has been focused on this possibility of changing pairing symmetry, where in the transition region both order parameters would be present and time-reversal symmetry would be broken. Here we report specific heat measurements in zero and applied magnetic fields down to 0.4 K of three individual single crystals ...


Glasses For Energy Storage: Advancing The Energy Density And Safety Of Batteries, Steve W. Martin 2017 Iowa State University

Glasses For Energy Storage: Advancing The Energy Density And Safety Of Batteries, Steve W. Martin

Steve W. Martin

No abstract provided.


Improved Method Of Co2 Laser Cutting Of Aluminum Nitride, Raathai Molian, Pranav Shrotriya, Pal Molian 2017 Iowa State University

Improved Method Of Co2 Laser Cutting Of Aluminum Nitride, Raathai Molian, Pranav Shrotriya, Pal Molian

Pranav Shrotriya

The traditional “evaporation∕melt and blow” mechanism of CO2 laser cutting of aluminum nitride (AlN) chip carriers and heat sinks suffers from energy losses due to its high thermal conductivity, formation of dross, decomposition to aluminum, and uncontrolled thermal cracking. In order to overcome these limitations, a thermochemical method that uses a defocused laser beam to melt a thin layer of AlN surface in oxygen environment was utilized. Subsequent solidification of the melt layer generated shrinkage and thermal gradient stresses that, in turn, created a crack along the middle path of laser beam and caused material separation through unstable crack ...


Microscopic Observations Of Voids In Anodic Oxide Films On Aluminum, R. Huang, Kurt R. Hebert, L. Scott Chumbley 2017 Iowa State University

Microscopic Observations Of Voids In Anodic Oxide Films On Aluminum, R. Huang, Kurt R. Hebert, L. Scott Chumbley

L. Scott Chumbley

The relationship was explored between nanoscale voids in anodic aluminum oxide films and the surface condition of aluminum samples prior to anodizing. Transmission electron microscopy (TEM) detected voids on the order of 10 nm in anodic films. Atomic force microscopy (AFM) of these films, obtained after partial oxide dissolution, revealed surface cavities; comparison of TEM and AFM suggested that the cavities were the oxide voids. AFM images after variable extents of oxide dissolution showed that the voids were distributed evenly through the inner 60% of the film thickness, indicating that they were formed at the metal-oxide interface during film growth ...


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