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Lattice Instability During Solid-Solid Structural Transformations Under A General Applied Stress Tensor: Example Of Si I → Si Ii With Metallization, Nikolai A. Zarkevich, Hao Chen, Valery I. Levitas, Duane D. Johnson 2018 Ames Laboratory

Lattice Instability During Solid-Solid Structural Transformations Under A General Applied Stress Tensor: Example Of Si I → Si Ii With Metallization, Nikolai A. Zarkevich, Hao Chen, Valery I. Levitas, Duane D. Johnson

Aerospace Engineering Publications

The density functional theory was employed to study the stress-strain behavior and elastic instabilities during the solid-solid phase transformation (PT) when subjected to a general stress tensor, as exemplified for semiconducting Si I and metallic Si II, where metallization precedes the PT, so stressed Si I can be a metal. The hydrostatic PT occurs at 76 GPa, while under uniaxial loading it is 11 GPa (3.7 GPa mean pressure), 21 times lower. The Si I → Si II PT is described by a critical value of the phase-field’s modified transformation work, and the PT criterion has only two parameters ...


Comparison Of Salicyl Hydroxamate Adsorption On Rare Earth Phosphates To Oxides And Carbonates, Stephanie Trant 2018 Montana Tech

Comparison Of Salicyl Hydroxamate Adsorption On Rare Earth Phosphates To Oxides And Carbonates, Stephanie Trant

Graduate Theses & Non-Theses

Adsorption behavior of the anionic collector salicyl hydroxamic acid (SHA) on a group of selected rare earth phosphates (REPs) was studied by means of experimental methods and modeling software. These REPs were then compared to rare earth carbonates (RECs) and rare earth oxides (REOs) to develop a trend. A suite of rare earth elements (REE) were studied that included light (LREE) and middle (MREE). Results for heavy (HREE) were inferred. Synthetic phosphate, oxide and carbonate powders of the rare earth elements Lanthanum (La), Cerium (Ce), Europium (Eu) and Dysprosium (Dy) were tested for these studies. Dysprosium phosphate was the only ...


Surface Chemistry And Modelling Of Salicyl Hydroxamic Acid Adsorption At The Surface Of Rare Earth Oxides, Carbonates And Phosphates, Marc F. Sime 2018 Montana Tech

Surface Chemistry And Modelling Of Salicyl Hydroxamic Acid Adsorption At The Surface Of Rare Earth Oxides, Carbonates And Phosphates, Marc F. Sime

Graduate Theses & Non-Theses

The adsorption mechanism of salicyl hydroxamic acid (SHA, C7H7O3N) on rare earth minerals was investigated using two complementary methods: precipitation studies and modelling. Precipitation studies showed that SHA adsorption occurs through a displacement of the hydroxide ion at the surface in an ion exchange mechanism, leading to surface precipitation and/or chemisorption. Surface precipitation predominates in the light rare earth oxides (LREOs), while chemisorption predominates in the heavier REOs. Modelling revealed that adsorption of SHA on the REM surface is dependent upon the orientation of SHA on the surface as well as the distance between rare earth elements sites on ...


Grain Boundary Motion Analysis, Jeremy Marquardt, Xiaorong Cai, Marisol Koslowski 2018 Purdue University

Grain Boundary Motion Analysis, Jeremy Marquardt, Xiaorong Cai, Marisol Koslowski

The Summer Undergraduate Research Fellowship (SURF) Symposium

Grain growth is a mechanism to relax residual stresses in thin films. These grains grow out of the thin film surface and are known as whiskers. These whiskers can cause short circuits, so developing scalable and cost effective solutions would increase the reliability and utility of tin electronics. A popular of method of examining tin whiskering is microscopic simulation, as it provides an accurate and cost effective way to predict the consequences of proposed models. Specifically examining the evolution of grain boundaries, this paper aims to present the results of grain boundary motion simulations through a generalized program that streamlines ...


Trends In Pressure-Induced Layer-Selective Half-Collapsed Tetragonal Phases In The Iron-Based Superconductor Family Aeafe(4)As(4), Vladislav Borisov, Paul C. Canfield, Roser Valentí 2018 Goethe University

Trends In Pressure-Induced Layer-Selective Half-Collapsed Tetragonal Phases In The Iron-Based Superconductor Family Aeafe(4)As(4), Vladislav Borisov, Paul C. Canfield, Roser Valentí

Ames Laboratory Accepted Manuscripts

By performing pressure simulations within density functional theory for the family of iron-based superconductors AeAFe4As4 with Ae=Ca, Sr, Ba and A=K, Rb, Cs we predict in these systems the appearance of two consecutive half-collapsed tetragonal transitions at pressures Pc1 and Pc2, which have a different character in terms of their effect on the electronic structure. We find that, similar to previous studies for CaKFe4As4, spin-vortex magnetic fluctuations on the Fe sublattice play a key role for an accurate structure prediction in these materials at zero pressure. We identify clear trends of critical pressures and discuss the relevance of ...


Microstructure And Mechanical Properties Of Selective Laser Melted Superalloy Inconel 625., Md Ashabul Anam 2018 University of Louisville

Microstructure And Mechanical Properties Of Selective Laser Melted Superalloy Inconel 625., Md Ashabul Anam

Electronic Theses and Dissertations

Selective Laser Melting (SLM), a powder based Additive Manufacturing (AM) process, has gained considerable attention in the aerospace, biomedical and automotive industries due to its many potential benefits, such as, capability of fabricating complex three-dimensional components, shortened design to product time, reduction in process steps, component mass reduction and material flexibility. This process uses metallic powder and is capable of fabricating complex structures with excellent microstructure which make SLM not only an improvement over other manufacturing processes but also innovative material processing technology. Inconel 625, a nickel-based super alloy is widely popular in aerospace, chemical and nuclear industries. This alloy ...


Emergent Magnetic Degeneracy In Iron Pnictides Due To The Interplay Between Spin-Orbit Coupling And Quantum Fluctuations, Morten H. Christensen, Peter P. Orth, Brian M. Andersen, Rafael M. Fernandes 2018 University of Minnesota

Emergent Magnetic Degeneracy In Iron Pnictides Due To The Interplay Between Spin-Orbit Coupling And Quantum Fluctuations, Morten H. Christensen, Peter P. Orth, Brian M. Andersen, Rafael M. Fernandes

Physics and Astronomy Publications

Recent experiments in iron pnictide superconductors reveal that, as the putative magnetic quantum critical point is approached, different types of magnetic order coexist over a narrow region of the phase diagram. Although these magnetic configurations share the same wave vectors, they break distinct symmetries of the lattice. Importantly, the highest superconducting transition temperature takes place close to this proliferation of near-degenerate magnetic states. In this Letter, we employ a renormalization group calculation to show that such a behavior naturally arises due to the effects of spin-orbit coupling on the quantum magnetic fluctuations. Formally, the enhanced magnetic degeneracy near the quantum ...


Persistent Correlation Between Superconductivity And Antiferromagnetic Fluctuations Near A Nematic Quantum Critical Point In Fese1−Xsx, P. Wiecki, Khusboo Rana, A. E. Böhmer, Y. Lee, Sergey L. Bud’ko, Paul C. Canfield, Yuji Furukawa 2018 Iowa State University and Ames Laboratory

Persistent Correlation Between Superconductivity And Antiferromagnetic Fluctuations Near A Nematic Quantum Critical Point In Fese1−Xsx, P. Wiecki, Khusboo Rana, A. E. Böhmer, Y. Lee, Sergey L. Bud’Ko, Paul C. Canfield, Yuji Furukawa

Ames Laboratory Accepted Manuscripts

We present 77Se-NMR measurements on FeSe1−xSx samples with sulfur content x=0%, 9%, 15%, and 29%. Twinned nematic domains are observed in the NMR spectrum for all samples except x=29%. The NMR spin-lattice relaxation rate shows that antiferromagnetic (AFM) fluctuations are initially enhanced between x=0% and x=9%, but are strongly suppressed for higher x values. The observed behavior of the AFM fluctuations parallels the superconducting transition temperature Tc in these materials, providing strong evidence for the primary importance of AFM fluctuations for superconductivity, despite the presence of nematic quantum criticality in the FeSe1−xSx system.


Effective Demagnetizing Factors Of Diamagnetic Samples Of Various Shapes, Ruslan Prozorov, Vladimir G. Kogan 2018 Iowa State University and Ames Laboratory

Effective Demagnetizing Factors Of Diamagnetic Samples Of Various Shapes, Ruslan Prozorov, Vladimir G. Kogan

Ames Laboratory Accepted Manuscripts

Effective demagnetizing factors that connect the sample magnetic moment with the applied magnetic field are calculated numerically for perfectly diamagnetic samples of various nonellipsoidal shapes. The procedure is based on calculating the total magnetic moment by integrating the magnetic induction obtained from a full three-dimensional (3D) solution of the Maxwell equations using an adaptive mesh. The results are relevant for superconductors (and conductors in ac fields) when the London penetration depth (or the skin depth) is much smaller than the sample size. Simple but reasonably accurate approximate formulas are given for practical shapes including rectangular cuboids, finite cylinders in axial ...


Non-Hysteretic First-Order Phase Transition With Large Latent Heat And Giant Low-Field Magnetocaloric Effect, F. Guillou, Arjun K. Pathak, Durga Paudyal, Yaroslav Mudryk, F. Wilhelm, A. Rogalev, Vitalij K. Pecharsky 2018 Ames Laboratory

Non-Hysteretic First-Order Phase Transition With Large Latent Heat And Giant Low-Field Magnetocaloric Effect, F. Guillou, Arjun K. Pathak, Durga Paudyal, Yaroslav Mudryk, F. Wilhelm, A. Rogalev, Vitalij K. Pecharsky

Materials Science and Engineering Publications

First-order magnetic transitions (FOMTs) with a large discontinuity in magnetization are highly sought in the development of advanced functional magnetic materials. Isosymmetric magnetoelastic FOMTs that do not perturb crystal symmetry are especially rare, and only a handful of material families, almost exclusively transition metal-based, are known to exhibit them. Yet, here we report a surprising isosymmetric FOMT in a rare-earth intermetallic, Eu2In. What makes this transition in Eu2In even more remarkable is that it is associated with a large latent heat and an exceptionally high magnetocaloric effect in low magnetic fields, but with tiny lattice discontinuities and negligible hysteresis. An ...


Current Progress And Future Challenges In Rare-Earth-Free Permanent Magnets, Jun Cui, Matthew J. Kramer, Lin Zhou, Fei Liu, Alexander Gabay, George Hadjipanayis, Balamurugan Balasubramanian, David Sellmyer 2018 Iowa State University and Ames Laboratory

Current Progress And Future Challenges In Rare-Earth-Free Permanent Magnets, Jun Cui, Matthew J. Kramer, Lin Zhou, Fei Liu, Alexander Gabay, George Hadjipanayis, Balamurugan Balasubramanian, David Sellmyer

Ames Laboratory Accepted Manuscripts

Permanent magnets (PM) are critical components for electric motors and power generators. Key properties of permanent magnets, especially coercivity and remanent magnetization, are strongly dependent on microstructure. Understanding metallurgical processing, phase stability and microstructural changes are essential for designing and improving permanent magnets. The widely used PM for the traction motor in electric vehicles and for the power generator in wind turbines contain rare earth elements Nd and Dy due to their high maximum energy product. Dy is used to sustain NdFeB's coercivity at higher temperature. Due to the high supply risk of rare earth elements (REE) such as ...


Magnetic Phase Diagram Of The Iron Pnictides In The Presence Of Spin-Orbit Coupling: Frustration Between C2 And C4 Magnetic Phases, Morten H. Christensen, Peter P. Orth, Brian M. Andersen, Rafael M. Fernandes 2018 University of Minnesota

Magnetic Phase Diagram Of The Iron Pnictides In The Presence Of Spin-Orbit Coupling: Frustration Between C2 And C4 Magnetic Phases, Morten H. Christensen, Peter P. Orth, Brian M. Andersen, Rafael M. Fernandes

Physics and Astronomy Publications

We investigate the impact of spin anisotropic interactions, promoted by spin-orbit coupling, on the magnetic phase diagram of the iron-based superconductors. Three distinct magnetic phases with Bragg peaks at (π,0) and (0,π) are possible in these systems: one C2 (i.e. orthorhombic) symmetric stripe magnetic phase and two C4 (i.e. tetragonal) symmetric magnetic phases. While the spin anisotropic interactions allow the magnetic moments to point in any direction in the C2 phase, they restrict the possible moment orientations in the C4 phases. As a result, an interesting scenario arises in which the spin anisotropic interactions favor a ...


Material Properties Of Laser Powder Bed Fusion Processed 316l Stainless Steel, Steven Keckler 2018 Montana Tech

Material Properties Of Laser Powder Bed Fusion Processed 316l Stainless Steel, Steven Keckler

Graduate Theses & Non-Theses

Laser powder bed fusion additive manufactured 316L stainless steel specimens were evaluated to establish a baseline for future research in determining an optimized energy density and build orientation. Test specimens were printed at various energy densities. At each energy density, tensile and fatigue specimens were printed at 0o (longitudinal), 45o, and 90o (transverse) orientation to the build plate. Tensile and high cycle fatigue tests were performed then representative fracture surfaces were analyzed. The apparent melt track and dendrite size were evaluated using grain analysis software. Static loading of the tensile specimens showed a marginal difference in UTS for specimens with ...


Investigation Of Narloy-Z Yield Strength In Response To Changes In Ingot Processing And Heat Treatment, Stanley C. Goto, Sarah E. Wattenberg 2018 California Polytechnic State University, San Luis Obispo

Investigation Of Narloy-Z Yield Strength In Response To Changes In Ingot Processing And Heat Treatment, Stanley C. Goto, Sarah E. Wattenberg

Materials Engineering

This study investigates the effect of cooling rate on the yield strength of NARloy-Z. NARloy-Z is a copper-based alloy with 3 wt.% silver and 0.5 wt.% zirconium. The types of NARloy-Z were classified by the ingot processing (old or new) and the material lot (old or new). There were three variations of NARloy-Z in this study: old processing and material (Old/Old); old processing and new material (Old/New); and new processing and material (New/New). NARloy-Z undergoes a braze thermal cycle and age (BTCA) heat treatment for its application, and a single cooling rate within the BTCA was ...


Temper Response Of A Vanadium Microalloy Steel, Bradley W. Hostetler 2018 California Polytechnic State University, San Luis Obispo

Temper Response Of A Vanadium Microalloy Steel, Bradley W. Hostetler

Materials Engineering

This investigation details the effect of a quench-and-temper processing treatment on the mechanical properties of a microalloy steel being considered for use as a pipeline flange. Microalloy steels are normally processed via Thermo-Mechanically Controlled Processing (TMCP) due to the increased strength from ferrite grain refinement; however, the geometry of a pipeline flange requires post processing beyond TMCP which diminishes the strengthening effect provided by TMCP. The purpose of this research project is to determine the mechanical properties produced when a vanadium microalloy steel is quenched and tempered. The two major considerations are the effect of tempering time on properties and ...


Anomalous 304 Stainless Steel Mechanical Properties In Medical Guide Wires, Andrew Joseph Freeman 2018 Cal Poly San Luis Obispo Materials Engineering Department

Anomalous 304 Stainless Steel Mechanical Properties In Medical Guide Wires, Andrew Joseph Freeman

Materials Engineering

Stainless steel medical guide wire cores, processed by Abbott Vascular, are returning anomalous mechanical properties upon strain hardening and heat treatment. As theory dictates, mechanical strength properties increase with strain hardening, and decrease with an annealing treatment. The opposite response is being observed. This is counter intuitive to fundamental materials knowledge, and a perfect materials engineering paradox. This project was designed to characterize these behaviors, and attempt to determine causation. To accomplish this, tensile testing of all processing steps mapped the mechanical property evolution of the wire. Published literature research revealed the potential of nitrogen and chromium solid state diffusion ...


Effects Of Head Formation And Heat Treatment On The Mechanical Properties Of Connecting Rod Bolts, Matthew R. Lauretta, Caleb A. Leavitt 2018 California Polytechnic State University, San Luis Obispo

Effects Of Head Formation And Heat Treatment On The Mechanical Properties Of Connecting Rod Bolts, Matthew R. Lauretta, Caleb A. Leavitt

Materials Engineering

Oliver Racing Parts (ORP; Charlevoix, Michigan) is looking to optimize their manufacturing process for high-strength connecting rod bolts. A high yield strength is desired for the bolts because deformation would result in catastrophic engine failure. The bolts were made of H11, a chromium hot-work tool steel; and MLX17, a precipitation hardenable stainless steel. Tensile testing was performed to determine the tensile and yield strengths of the bolts. Fracture surfaces were imaged via scanning electron microscopy to characterize the failure modes. To observe the effects of bolt heading on microstructure and bolt strength, two batches of MLX17 were prepared; one batch ...


Antiferromagnetic Order In Cak(Fe1-Xnix)(4)As-4 And Its Interplay With Superconductivity, Andreas Kreyssig, John M. Wilde, Anna E. Böhmer, W. Tian, William R. Meier, Bing Li, Benjamin G. Ueland, Mingyu Xu, Sergey L. Bud’ko, Paul C. Canfield, Robert J. McQueeney, Alan I. Goldman 2018 Iowa State University and Ames Laboratory

Antiferromagnetic Order In Cak(Fe1-Xnix)(4)As-4 And Its Interplay With Superconductivity, Andreas Kreyssig, John M. Wilde, Anna E. Böhmer, W. Tian, William R. Meier, Bing Li, Benjamin G. Ueland, Mingyu Xu, Sergey L. Bud’Ko, Paul C. Canfield, Robert J. Mcqueeney, Alan I. Goldman

Ames Laboratory Accepted Manuscripts

The magnetic order in CaK(Fe1−xNix)4 As4 (1144) single crystals (x=0.051 and 0.033) has been studied by neutron diffraction. We observe magnetic Bragg peaks associated with the same propagation vectors as found for the collinear stripe antiferromagnetic (AFM) order in the related BaFe2As2 (122) compound. The AFM state in 1144 preserves tetragonal symmetry and only a commensurate, noncollinear structure with a hedgehog spin-vortex crystal (SVC) arrangement in the Fe plane and simple AFM stacking along the c direction is consistent with our observations. The SVC order is promoted by the reduced symmetry in the FeAs ...


An Evaluation Of Ultrasonic Shot Peening And Abrasive Flow Machining As Surface Finishing Processes For Selective Laser Melted 316l, Rhys Gilmore 2018 California Polytechnic State University, San Luis Obispo

An Evaluation Of Ultrasonic Shot Peening And Abrasive Flow Machining As Surface Finishing Processes For Selective Laser Melted 316l, Rhys Gilmore

Master's Theses and Project Reports

Additive Manufacturing, and specifically powder bed fusion processes, have advanced rapidly in recent years. Selective Laser Melting in particular has been adopted in a variety of industries from biomedical to aerospace because of its capability to produce complex components with numerous alloys, including stainless steels, nickel superalloys, and titanium alloys. Post-processing is required to treat or solve metallurgical issues such as porosity, residual stresses, and surface roughness. Because of the geometric complexity of SLM produced parts, the reduction of surface roughness with conventional processing has proven especially challenging. In this Thesis, two processes, abrasive flow machining and ultrasonic shot peening ...


In Situ Sem Solidification Study Of Ga And Egain: A Characterization Technique For Monitoring The Microstructural Evolution Of Liquid Metals, Jeremy Geovann Del Aguila 2018 California Polytechnic State University, San Luis Obispo

In Situ Sem Solidification Study Of Ga And Egain: A Characterization Technique For Monitoring The Microstructural Evolution Of Liquid Metals, Jeremy Geovann Del Aguila

Materials Engineering

Scanning electron microscopy (SEM) video recording is used to characterize the solidification of small volumes of 99.999% pure gallium (Ga) and eutectic gallium-indium (eGaIn) under a high vacuum environment. Specimen are superheated to 55℃ using a hot plate, cast into spherical droplets, and cooled in situ by means of a Peltier cooling stage. Special attention is given to the preparation of the specimen prior to viewing because of gallium and its alloys’ nature to form an oxide layer when melted and air cooled. The oxide acts as a skin that inhibits the observation of microstructural features during solidification. Heated ...


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