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Type Wojes, Ryan; Kolli, R. Prakash
  Publication Mechanical Polishing Volume Manuscript
Pages 2006
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Abbreviated Series Title These procedures work for harder metals. Anything above 300 HVN should be fine. For softer materials you will need to polish at each step for a longer time with a lower force.
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no NU @ karnesky @ 1746
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Vaynman, Semyon; Isheim, Dieter; Kolli, R. Prakash; Bhat, Shrikant P.; Seidman, David N.; Fine, Morris E. High-Strength Low-Carbon Ferritic Steel Containing Cu-Fe-Ni-Al-Mn Precipitates Journal Article 2008 Metallurgical and Materials Transactions A 39 2 363-373 High-Strength; Low-Carbon; Ferritic; Steel; Precipitates An investigation of a low-carbon, Fe-Cu–based steel, for Naval ship hull applications, with a yield strength of 965 MPa, Charpy V-notch absorbed impact-energy values as high as 74 J at –40 °C, and an elongation-to-failure greater than 15 pct, is presented. The increase in strength is derived from a large number density (approximately 1023 to 1024 m−3) of copper-iron-nickel-aluminum-manganese precipitates. The effect on the mechanical properties of varying the thermal treatment was studied. The nanostructure of the precipitates found within the steel was characterized by atom-probe tomography. Additionally, initial welding studies show that a brittle heat-affected zone is not formed adjacent to the welds. 1073-5623 no NU @ m-krug @ 10195
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Kolli, R.Prakash; Seidman, David N. Coarsening kinetics of Cu-rich precipitates in a concentrated multicomponent Fe–Cu based steel Journal Article 2011 International Journal of Materials Research (formerly Zeitschrift fuer Metallkunde) 102 09 1115-1124 Coarsening, Phase separation, Fe-Cu alloys, Atom-probe tomography, Precipitation The coarsening kinetics of Cu-rich precipitates in a concentrated multicomponent Fe–Cu based steel, containing 1.12 at.% Cu, aged at 550 °C or at 550 °C plus 2 h at 200 °C is investigated. The temporal evolution of the precipitates, heterophase interfaces, and &#945;-Fe matrix compositions and precipitate morphology are presented. Coarsening time exponents are determined for the mean radius, <R(t)>, and number density, NV(t), and compared to the Lifshitz–Slyzov–Wagner model for coarsening, modified for concentrated multicomponent alloys by Umantsev–Olson. The experimental results indicate that <R(t)> and NV(t) are in reasonable agreement with Umantsev–Olson model behavior. Additionally, we compare the results to earlier investigations of similar concentrated multicomponent steels containing 1.82 at.% Cu and 1.17 at.% Cu, aged at 500 °C. 1862-5282 no NU @ karnesky @ 2186 11293
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Kolli, R.P.; Mao, Z.; Seidman, D.N.; Keane, D.T. Identification of a Ni[sub:0.5](Al[sub:0.5 - x]Mn[sub:x]) B2 phase at the heterophase interfaces of Cu-rich precipitates in an alpha-Fe matrix Journal Article 2007 Applied Physics Letters Appl. Phys. Lett. 91 24 241903-3 ab initio calculations; aluminium alloys; manganese alloys; nickel alloys; precipitation; stoichiometry; surface segregation A phase with the stoichiometry Ni0.5(Al0.5&#8722;xMnx) is observed at heterophase interfaces of Cu-rich precipitates in an alpha-Fe matrix, utilizing atom-probe tomography. First-principles calculations are utilized to determine the substitutional energies, yielding EMn-->Ni=0.916 eV atom&#8722;1 and EMn-->Al=&#8722;0.016 eV atom&#8722;1 indicating that the manganese atoms prefer substituting at Al sublattice sites instead of Ni sites. A synchrotron radiation experiment demonstrates that the identified phase possesses the B2 structure. Aip no NU @ karnesky @ 10170
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Kolli, R. Prakash; Seidman, David N. Comparison of Compositional and Morphological Atom-Probe Tomography Analyses for a Multicomponent Fe-Cu Steel Journal Article 2007 Microscopy & Microanalysis Microsc. Microanal. 13 4 272-284 precipitate morphology, concentration profiles, atom-probe tomography, maximum separation distance, envelope method, proxigram, Fu-Cu steel, high-strength low-carbon ~HSLC! steel A multicomponent Fe-Cu based steel is studied using atom-probe tomography. The precipitates are identified using two different methodologies and subsequent morphological and compositional results are compared. The precipitates are first identified using a maximum separation distance algorithm, the envelope method, and then by a concentration threshold method, an isoconcentration surface. We discuss in detail the proper selection of the parameters needed to delineate precipitates utilizing both methods. The results of the two methods exhibit a difference of 44 identified precipitates, which can be attributed to differences in the basis of both methods and the sensitivity of our results to user-prescribed parameters. The morphology of the precipitates, characterized by four different precipitate radii and precipitate size distribution functions ~PSDs!, are compared and evaluated. A variation of less than ;8% is found between the different radii. Two types of concentration profiles are compared, giving qualitatively similar results. Both profiles show Cu-rich precipitates containing Fe with elevated concentrations of Ni, Al, and Mn near the heterophase interfaces. There are, however, quantitative disagreements due to differences in the basic foundations of the two analysis methods. no NU @ karnesky @ 713
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Kolli, R. Prakash; Seidman, David N. Asymmetric Chemical Composition Profiles of Nanoscale Precipitates in a Multi-component Alloy Studied by 3-D Atom-Probe Tomography Journal Article 2006 Scripta Materialia Scripta Mater. Submitted 3-D atom-probe tomography, Fe-Cu steels, phase transformations, heterogeneous segregation, precipitation Compositional profiles of precipitates in a multi-component Fe-Cu steel are obtained by 3-D local-electrode atom-probe (LEAP) tomography. Adjacent Cu-rich and Ni-Al-Mn rich regions in the 1-hour aged alloy evolve temporally into a Cu-rich precipitate core enveloped by a Ni-Al-Mn (0.42:0.49:0.09) enriched spherical-shell in the 1024-hour aged alloy. The compositions of the shells are demonstrated, for the first time, to be asymmetric. We propose this results from precipitation of Cu-rich precipitates followed by heterogeneous nucleation of Ni-Al-Mn on them and subsequent diffusional growth. PDF removed at request of author no NU @ karnesky @ 773
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Kolli, R. Prakash; Seidman, David N. The temporal evolution of the decomposition of a concentrated multicomponent Fe-Cu based steel Manuscript no NU @ m-krug @ 9834
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Kolli, R. Prakash; Seidman, D.N. The temporal evolution of the decomposition of a concentrated multicomponent Fe-Cu-based steel Journal Article 2008 Acta Materialia 56 9 2073-2088 Coarsening; Fe-Cu alloy; Phase separation; Atom-probe tomography; Interfacial segregation The nucleation (to a limited extent), growth and coarsening behavior of Cu-rich precipitates in a concentrated multicomponent Fe-Cu-based steel aged at 500 °C from 0.25 to 1024 h is investigated. The temporal evolution of the precipitates, heterophase interfaces, matrix compositions and precipitate morphologies are presented. With increasing time, Cu partitions to the precipitates, Ni, Al and Mn partition to the interfacial region, whereas Fe and Si partition to the matrix. Coarsening time exponents are determined for the mean radius, <R(t)>, number density, NV(t), and supersaturations, which are compared to the Lifshitz-Slyzov-Wagner (LSW) model for coarsening, modified for concentrated multicomponent alloys by Umantsev and Olson (UO). The experimental results indicate that the alloy does not strictly follow UO model behavior. Additionally, we delineate the formation of a Ni-Al-Mn shell with a stoichiometric ratio of 0.51:0.41:0.08 at 1024 h, which reduces the interfacial free energy between the precipitates and the matrix. no NU @ p-kolli @ 10373
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Kolli, R. Prakash; Mao, Zugang; Keane, D. T.; Seidman, David N. Identification of a Ni0.5(Al0.5-xMnx) B2 Phase at the Heterophase Interfaces of Cu-rich Precipitates in an a-Fe Matrix Journal Article 2007 Applied Physics Letters Accepted A phase with the stoichiometry Ni0.5(Al0.5-xMnx) is observed at heterophase interfaces of Cu-rich precipitates in an &#945;-Fe matrix, utilizing atom-probe tomography. First-principles calculations are utilized to determine the substitutional energies, yielding E Mn &#8594;Ni = 0.916 eV atom-1 and E Mn &#8594;Al = &#8722;0.016 eV atom-1, indicating that the manganese atoms prefer substituting at Al sub- lattice sites instead of Ni-sites. A synchrotron radiation experiment demonstrates that the identified phase possesses the B2 structure. no NU @ karnesky @ 9945
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Kolli, R. Prakash Kolli; Wojes, Ryan M.; Zaucha, Stephanie; Seidman, David N. A subnanoscale study of the nucleation, growth, and coarsening kinetics of Cu-rich precipitates in a multicomponent Fe–Cu based steel Journal Article 2008 International Journal of Materials Research Int. J. Mater. Res. 05 513-527 Nucleation; Growth; Coarsening; Fe-Cu alloy; Atom-probe tomography The nucleation, growth, and coarsening kinetics of Cu-rich precipitates in a multicomponent Fe–Cu based steel, containing 1.17 at.% Cu, aged at 500°C for up to 1024 h are investigated. The temporal evolution of the precipitate, heterophase interface, matrix compositions and precipitate morphology are presented. Coarsening temporal exponents are determined for mean radius, [R(t)], number density, NV(t), and supersaturations, and are compared to the Lifshitz–Slyzov–Wagner model for coarsening, modified for multicomponent alloys by Umantsev and Olson. The experimental results indicate that the alloy does not strictly follow Umantsev–Olson model behavior. Additionally, we compare the results to an investigation of a similar multicomponent steel containing 1.82 at.% Cu and to results in the literature. Furthermore, we present a Thermo-Calc determined phase diagram. no NU @ p-kolli @ 10374
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