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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 ...


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 ...


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 ...


Effects Of Schmid Factor And Slip Nucleation On Deformation Mechanism In Columnar-Grained Nanotwinned Ag And Cu, Valery Borovikov, Mikhail I. Mendelev, Alexander H. King, Richard Lesar 2017 The Ames Laboratory

Effects Of Schmid Factor And Slip Nucleation On Deformation Mechanism In Columnar-Grained Nanotwinned Ag And Cu, Valery Borovikov, Mikhail I. Mendelev, Alexander H. King, Richard Lesar

Richard Alan Lesar

We report the results of a molecular dynamics study of the effect of texture on the yield and peak stresses in columnar-grained nanotwinned Ag and Cu. The simulations suggest that in pure nanotwinned face-centered cubic metals, the strength is determined primarily by the cooperation or competition between two major factors: the magnitude of the Schmid factors for the available slip systems and the effectiveness of grain boundaries (and their triple-junctions) in generating dislocations. These factors and their relative impact depend on the geometry of the specimen relative to the applied stress, which is typically reflected in the texture of the ...


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 ...


Validation Of Tool Mark Comparisons Obtained Using A Quantitative, Comparative, Statistical Algorithm, L. Scott Chumbley, Max D. Morris, M. James Kreiser, Charles Fisher, Jeremy Craft, Lawrence Genalo, Stephen Davis, David Faden, Julie Kidd 2017 Iowa State University

Validation Of Tool Mark Comparisons Obtained Using A Quantitative, Comparative, Statistical Algorithm, L. Scott Chumbley, Max D. Morris, M. James Kreiser, Charles Fisher, Jeremy Craft, Lawrence Genalo, Stephen Davis, David Faden, Julie Kidd

L. Scott Chumbley

A statistical analysis and computational algorithm for comparing pairs of tool marks via profilometry data is described. Empirical validation of the method is established through experiments based on tool marks made at selected fixed angles from 50 sequentially manufactured screwdriver tips. Results obtained from three different comparison scenarios are presented and are in agreement with experiential knowledge possessed by practicing examiners. Further comparisons between scores produced by the algorithm and visual assessments of the same tool mark pairs by professional tool mark examiners in a blind study in general show good agreement between the algorithm and human experts. In specific ...


A New Method For Strengthening Gold, Alan M. Russell, Kai Xu, L. Scott Chumbley, James Parks, Joel Harringa 2017 Iowa State University

A New Method For Strengthening Gold, Alan M. Russell, Kai Xu, L. Scott Chumbley, James Parks, Joel Harringa

L. Scott Chumbley

Metal-metal composites were first produced in a copper matrix in the 1970’s, and they have since been produced in several other binary metal systems. This strengthening technique reinforces a ductile metal matrix with a ductile metal second phase. In some binary systems, this technique confers extraordinarily high strength and hardness while still maintaining low electrical resistivity. This article reports on the first gold matrix metal-metal composite, which was produced by deformation processing a 90%Au-10%Ag powder compact. The Au-Ag specimen studied had an ultimate tensile strength of 550 MPa and an electrical resistivity only 8% higher than that ...


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 ...


Statistical Confirmation Of Empirical Observations Concerning Tool Mark Striae, D. Faden, J. Kidd, J. Craft, Max D. Morris, Lawrence Genalo, J. Kreiser, S. Davis 2017 Iowa State University

Statistical Confirmation Of Empirical Observations Concerning Tool Mark Striae, D. Faden, J. Kidd, J. Craft, Max D. Morris, Lawrence Genalo, J. Kreiser, S. Davis

Lawrence Genalo

Too/marks produced by 44 sequentially manufactured screwdriver tips have been characterized for surface roughness using a pro.filometer. Too/marks were produced in lead at angles of 30 o, 60 o, and 85 °. A computer program developed to compare and match the pro.filometer data has been used to show that marks from a single tip produced at similar angles yield much higher correlation values than marks produced from the same tip but at different angles. This analysis provides statistical support for the widely-accepted empirical observation that too/mark striae must be reproduced at similar angles in order to ...


Weak Anti-Localization And Quantum Oscillations Of Surface States In Topological Insulator Bi2se2te, Lihong Bao, Liang He, Nicholas R. Meyer, Xufeng Kou, Peng Zhang, Zhi-gang Chen, Alexei V. Fedorov, Trevor M. Riedemann, Thomas A. Lograsso, Kang L. Wang, Gary Tuttle, Faxian Xiu 2017 Iowa State University

Weak Anti-Localization And Quantum Oscillations Of Surface States In Topological Insulator Bi2se2te, Lihong Bao, Liang He, Nicholas R. Meyer, Xufeng Kou, Peng Zhang, Zhi-Gang Chen, Alexei V. Fedorov, Trevor M. Riedemann, Thomas A. Lograsso, Kang L. Wang, Gary Tuttle, Faxian Xiu

Gary Tuttle

Topological insulators, a new quantum state of matter, create exciting opportunities for studying topological quantum physics and for exploring spintronic applications due to their gapless helical metallic surface states. Here, we report the observation of weak anti-localization and quantum oscillations originated from surface states in Bi2Se2Te crystals. Angle-resolved photoemission spectroscopy measurements on cleaved Bi2Se2Te crystals show a well-defined linear dispersion without intersection of the conduction band. The measured weak anti-localization effect agrees well with the Hikami-Larkin-Nagaoka model and the extracted phase coherent length shows a power-law dependence with temperature ( ∼T−0.44), indicating the presence of the surface states. More ...


Atomistic Clustering-Ordering And High-Strain Deformation Of An Al0.1crcofeni High-Entropy Alloy, Aayush Sharma, Prashant Signh, Duane D. Johnson, Peter K. Liaw, Ganesh Balasubramanian 2017 Iowa State University

Atomistic Clustering-Ordering And High-Strain Deformation Of An Al0.1crcofeni High-Entropy Alloy, Aayush Sharma, Prashant Signh, Duane D. Johnson, Peter K. Liaw, Ganesh Balasubramanian

Ganesh Balasubramanian

Computational investigations of structural, chemical, and deformation behavior in high-entropy alloys (HEAs), which possess notable mechanical strength, have been limited due to the absence of applicable force fields. To extend investigations, we propose a set of intermolecular potential parameters for a quinary Al-Cr-Co-Fe-Ni alloy, using the available ternary Embedded Atom Method and Lennard-Jones potential in classical molecular-dynamics simulations. The simulation results are validated by a comparison to first-principles Korringa-Kohn-Rostoker (KKR) - Coherent Potential Approximation (CPA) [KKR-CPA] calculations for the HEA structural properties (lattice constants and bulk moduli), relative stability, pair probabilities, and high-temperature short-range ordering. The simulation (MD)-derived properties are ...


Atomistic Clustering-Ordering And High-Strain Deformation Of An Al0.1crcofeni High-Entropy Alloy, Aayush Sharma, Prashant Signh, Duane D. Johnson, Peter K. Liaw, Ganesh Balasubramanian 2017 Iowa State University

Atomistic Clustering-Ordering And High-Strain Deformation Of An Al0.1crcofeni High-Entropy Alloy, Aayush Sharma, Prashant Signh, Duane D. Johnson, Peter K. Liaw, Ganesh Balasubramanian

Duane D. Johnson

Computational investigations of structural, chemical, and deformation behavior in high-entropy alloys (HEAs), which possess notable mechanical strength, have been limited due to the absence of applicable force fields. To extend investigations, we propose a set of intermolecular potential parameters for a quinary Al-Cr-Co-Fe-Ni alloy, using the available ternary Embedded Atom Method and Lennard-Jones potential in classical molecular-dynamics simulations. The simulation results are validated by a comparison to first-principles Korringa-Kohn-Rostoker (KKR) - Coherent Potential Approximation (CPA) [KKR-CPA] calculations for the HEA structural properties (lattice constants and bulk moduli), relative stability, pair probabilities, and high-temperature short-range ordering. The simulation (MD)-derived properties are ...


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

Materials Science and Engineering Publications

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 ...


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