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Park, J.H.; Lee, Y.S.; Nam, W.J.; Park, K.T. |
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Publication |
Comparison of compressive deformation of ultrafine-grained 5083 Al alloy at 77 and 298 K |
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Journal Article |
Pages |
2005 |
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Abstract |
Metallurgical And Materials Transactions A-Physical Metallurgy And Materials Science |
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Corporate Author |
Metall. Mater. Trans. A-Phys. Metall. Mater. Sci. |
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36a |
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Editor |
5 |
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Summary Language |
1365-1368 |
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Abbreviated Series Title |
The compression behaviors of well-annealed coarse-grained (CG) and ultrafine-grained (UFG) 5083 Al alloys at 77 and 298 K were compared. For the CG alloy, stage II and III strain hardening were dominant at 77 and 298 K, respectively, depending on the completeness of dislocation cell formation. The UFG alloy exhibited the elastic-near perfectly plastic behavior without distinctive dislocation cell formation at both temperatures. For both alloys, the flow stress at 77 K was much higher than that at 298 K. |
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Series Issue |
Hanbat Natl Univ, Div Adv Mat Sci & Engn, Taejon 305719, South Korea, Email: ktpark@hanbat.ac.kr |
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Minerals Metals Materials Soc |
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1073-5623 |
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ISI:000228797500029 |
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NU @ karnesky @ |
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10027 |
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Muraleedharan, K.; Balamuralikrishnan, R.; Das, N. |
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TEM and 3D atom probe characterization of DMS4 cast nickel-base superalloy |
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Journal Article |
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2009 |
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Journal of Materials Science |
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J. Mater. Sci. |
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44 |
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9 |
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2218-2225 |
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Cast nickel-base superalloys possess the required mechanical properties (creep resistance and stress rupture life) at elevated temperatures that make them suitable for turbine blades in aero-engines. The origin of these properties lies in the presence of a simple two phase [gamma]-[gamma]' microstructure (with cuboidal [gamma]' particles dispersed in a [gamma] matrix), in spite of the presence of several alloying elements. The cuboidal nature of the [gamma]' particles arises from an optimal misfit between the two phases, which is a function of the composition of [gamma] and [gamma]' phases. In addition, several microstructural issues arising out of the partitioning of the alloying elements influences directly the deformation mechanisms in the [gamma] and [gamma]', and therefore the mechanical properties of the alloy. In this article, we discuss how some of these microstructural issues have been investigated in DMS4, a cast single crystal superalloy, experimentally using TEM and 3DAP techniques. |
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NU @ karnesky @ |
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10534 |
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Galtrey, M.J.; Oliver, R.A.; Kappers, M.J.; McAleese, C.; Zhu, D.; Humphreys, C.J.; Clifton, P.H.; Larsen, D.; Cerezo, A. |
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Atom probe revels the structure of InxGe1-xN based quantum wells in three dimensions |
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Journal Article |
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2008 |
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Physica Status Solidi B-Basic Solid State Physics |
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Phys. Status Solidi B-Basic Solid State Phys. |
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245 |
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5 |
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861-867 |
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The three-dimensional atom probe has been used to characterize InxGa1-xN based multiple quantum well structures emitting from the green to the ultra-violet with sub-nanometre resolution over a 100 nm field of view. The results show gross discontinuities and compositional variations within the UV-emitting quantum well layers on a 20-100 nm length scale. We propose that these may contribute to the high efficiency of this structure: In addition, the analysis shows the presence of indium in the barrier layers of all the samples, whether or not there was an indium precursor present during barrier growth. The distribution of indium within the blue- and green-emitting InxGa1-xN quantum wells is also analyzed, and we find no evidence that InxGa1-xN with a range of compositions is not a random alloy, and so rule out indium clustering as the cause of the reported carrier localization in these structures. The upper interface of each quantum well layer is shown to be rougher and more diffuse than the lower. and the existence of monolayer steps in the interfaces that could effectively localize carriers at room temperature is revealed. (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. |
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Univ Cambridge, Dept Mat Sci & Met, Cambridge CB2 3QZ, England, Email: mjg73@cam.ac.uk |
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Wiley-V C H Verlag Gmbh |
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English |
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0370-1972 |
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ISI:000256242300017 |
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NU @ m-krug @ |
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10392 |
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Bakhtizin, R. Z.; Valeev, V. G. |
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Microroughness field emission electron energy distribution and electron-phonon interaction spectroscopy near the metal surface |
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Journal Article |
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1988 |
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Physica Status Solidi A |
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Phys. Stat. Sol. A |
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108 |
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1 |
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251-255 |
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Field Emission |
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Field electron emission is considered from microtips on the metal surface. The possibility is shown of field emission spectroscopy of electron-phonon interaction near the emitting surface and the influence is studied of an increase in the surface potential barrier transparency by application of a weak high-frequency field altering the character of the field electron energy distribution in such a system. |
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4012 |
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Y.K. Chen-Wiegart, S. Wang, W.K. Lee, I. McNulty, P.W. Voorhees, D.C. Dunand |
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In situ Imaging of Dealloying during Nanoporous Gold Formation by Transmission X-ray Microscopy |
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Journal Article |
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2013 |
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Acta Materialia |
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61 |
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1118-1125 |
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NU @ michaeljsrawlings @ |
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11454 |
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Lee, Thomas C. M. |
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ON ALGORITHMS FOR ORDINARY LEAST SQUARES REGRESSION SPLINE FITTING: A COMPARATIVE STUDY |
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Journal Article |
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2002 |
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Journal of Statistical Computation and Simulation |
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72 |
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8 |
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647-663 |
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Bivariate smoothing; Generalized cross-validation; Genetic algorithms; Regression spline; Stepwise selection |
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Regression spline smoothing is a popular approach for conducting nonparametric regression. An important issue
associated with it is the choice of a ‘‘theoretically best’’ set of knots. Different statistical model selection
methods, such as Akaike’s information criterion and generalized cross-validation, have been applied to derive
different ‘‘theoretically best’’ sets of knots. Typically these best knot sets are defined implicitly as the optimizers
of some objective functions. Hence another equally important issue concerning regression spline smoothing is
how to optimize such objective functions. In this article different numerical algorithms that are designed for
carrying out such optimization problems are compared by means of a simulation study. Both the univariate and
bivariate smoothing settings will be considered. Based on the simulation results, recommendations for choosing a
suitable optimization algorithm under various settings will be provided. |
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NU @ karnesky @ |
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860 |
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Park, Kyung-Tae; Hwang, Duck-Young; Lee, Young-Kook; Kim, Young-Kuk; Shin, Dong Hyuk |
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High strain rate superplasticity of submicrometer grained 5083 Al alloy containing scandium fabricated by severe plastic deformation |
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Journal Article |
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2003 |
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Materials Science and Engineering A |
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Mater. Sci. Eng. A |
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341 |
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1-2 |
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273-281 |
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High strain rate superplasticity; 5083 Al alloy; Scandium; Severe plastic deformation; Ultrafine grains |
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High strain rate superplasticity (HSRS) was obtained in a commercial 5083 Al alloy by introducing a ultrafine grained structure of 0.3 small mu, Greekm through severe plastic deformation and by adding a dilute amount of scandium (Sc) as a microstructure stabilizer. Tensile tests were carried out on the as-processed sample at temperatures of 623–823 K and initial strain rates of 1×10−3–1×100 s−1. The maximum elongation to failure of 740% was obtained at 773 K and 1×10−2 s−1. HSRS of the alloy was attributed to the combined effects of dynamic recrystallization and preservation of fine recrystallized grains by the presence of Sc. The mechanical behavior of the alloy at 773 K was characterized by a sigmoidal behavior in a plot of stress vs strain rate in the double logarithmic scale. The origin of the sigmoidal behavior was discussed in terms of microstructural evolution during superplastic deformation. An examination of the fractured samples revealed that failure occurred in a brittle manner related to cavitation rather than necking. Cavity stringers were formed parallel to the tensile axis by interlinkage of jagged-shaped isolated cavities along grain boundaries aligned to the tensile axis. |
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no |
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NU @ karnesky @ |
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585 |
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Ahmad, Zaki; Ul-Hamid, Anwar; B.J., Abdul-Aleem |
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The corrosion behavior of scandium alloyed Al 5052 in neutral sodium chloride solution |
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Journal Article |
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2001 |
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Corrosion Science |
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43 |
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7 |
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1227-1243 |
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Corrosion; Al–Mg–Sc; Age-hardening; Microstructure; Pitting potential; Polarization |
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Alloying with scandium has a strong influence on the strengthening and weight saving characteristics of Al–2.5Mg alloys. Scandium addition (0.1–0.3 wt.%) to Al–2.5Mg alloys does not introduce any appreciable loss in their resistance to corrosion in 3.5 wt.% NaCl. The corrosion behavior of these alloys is not significantly affected by age hardening. Because of a unique combination of outstanding mechanical properties and a good resistance to corrosion Al–Mg alloys containing scandium represent a major improvement over the more familiar Al–Mg alloys. |
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no |
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NU @ karnesky @ |
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435 |
| Permanent link to this record |
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Lee, Woei-Shyan; Chen, Tao-Hsing |
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Rate-dependent deformation and dislocation substructure of Al–Sc alloy |
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Journal Article |
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2006 |
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Scripta Materialia |
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Scripta Mater. |
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54 |
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8 |
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1463-1468 |
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Al–Sc alloy; Strain rate effect; Activation volume; Dislocation |
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High strength aluminum–scandium (Al–Sc) alloy is impacted at strain rates ranging from 1.2 × 103 s−1 to 5.8 × 103 s−1 at room temperature. The deformation behaviour of Al–Sc alloy is highly dependent on the strain rate. A higher strain rate increases the dislocation density, thereby reducing the size of the dislocation cells. |
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no |
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NU @ karnesky @ |
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653 |
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Park, Kyung-Tae; Lee, Hang-Jae; Lee, Chong Soo; Nam, Won Jong; Shin, Dong Hyuk |
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Enhancement of high strain rate superplastic elongation of a modified 5154 Al by subsequent rolling after equal channel angular pressing |
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Journal Article |
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2004 |
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Scripta Materialia |
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Scripta Mater. |
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51 |
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6 |
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479-483 |
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Aluminum alloy; Superplasticity; Equal channel angular pressing; Rolling |
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Subsequent rolling after equal channel angular pressing (ECAP) resulted in a considerable enhancement of the high strain rate superplastic elongation of a modified 5154 Al alloy, compared to that of the alloy subjected to the identical ECAP strain without rolling. The mechanical data revealed that the deformation of the former was governed by grain boundary sliding but that of the latter was dominated by viscous glide. |
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NU @ karnesky @ |
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586 |
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