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Van Deventer, E.H.; MacLaren, V.A.; Maroni, V.A. |
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Hydrogen permeation characteristics of aluminum-coated and aluminum-modified steels |
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Journal Article |
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1980 |
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Journal of Nuclear Materials |
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88 |
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1 |
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168-173 |
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NU @ karnesky @ |
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10331 |
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Moreno-Gobbi, A.; Zamir, G.; Eiras, J.A. |
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Ultrasonic investigation of the interaction of hydrogen-dislocations in copper crystals |
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Journal Article |
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Materials Science and Engineering: A |
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In Press, Corrected Proof |
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Ultrasound; Dislocations; Hydrogen embrittlement; Copper |
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In this paper we present experimental data of ultrasonic velocity and attenuation obtained in a high purity crystalline sample of copper hydrogenated by gaseous charge. The sample is oriented in the <1 1 1> crystallographic direction and aged for this work in three stages between 64 and 97 days. The results indicate that the hydrogen is mainly segregated at the dislocation core, inhibiting the hydrogen Snoek-Köster relaxations verified at earlier ageing stages. Despite this, a contribution to viscosity in the kink-chain resonance is provided by the mobile hydrogen in the dislocation core by its side movement along the dislocation line. At temperatures at which the hydrogen begins to freeze in the lattice the geometrical kinks find a gradual increase on the hindering of their movements along dislocation lines, becoming immobile when the hydrogen is completely frozen in the crystal, anchoring the dislocations in short loops. Although the viscosity associated with the mobile hydrogen is removed, the resonance associated with geometrical kinks is not completely cancelled. The interaction of hydrogen-dislocation can be fully described in terms of kinks in dislocations. |
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0921-5093 |
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NU @ karnesky @ |
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11026 |
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Venkateswarlu, K.; Rajinikanth, V.; Ray, Ajoy Kumar; Xu, Cheng; Langdon, Terence G. |
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The characteristics of aluminum-scandium alloys processed by ECAP |
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Journal Article |
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2010 |
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Materials Science and Engineering: A |
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527 |
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6 |
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1448-1452 |
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Aluminum alloys; Equal-channel angular pressing; Scandium; Tensile testing; Ultrafine grains |
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Aluminum-scandium alloys were prepared having different scandium additions of 0.2, 1.0 and 2.0wt.% and these alloys were processed by equal-channel angular pressing (ECAP) at 473K. The results show the grain refinement of the aluminum matrix and the morphology of the Al3Sc precipitates depends strongly on the scandium concentration. The tensile properties were evaluated after ECAP by pulling to failure at initial strain rates from 1.010-3 to 1.010-1s-1. The Al-1% Sc alloy exhibited the highest tensile strength of ~250MPa at a strain rate of 1.010-1s-1. This alloy also exhibited a superior grain refinement of ~0.4[mu]m after ECAP where this is attributed to a smaller initial grain size and an optimum volume fraction of dispersed Al3Sc precipitates having both micrometer and nanometer sizes. |
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0921-5093 |
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NU @ karnesky @ |
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10711 |
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Meng, Gang; Li, Bolong; Li, Hongmei; Huang, Hui; Nie, Zuoren |
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Hot deformation and processing maps of an Al-5.7 wt.%Mg alloy with erbium |
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Journal Article |
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2009 |
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Materials Science and Engineering: A |
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517 |
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1-2 |
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132-137 |
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Hot deformation; Processing maps; Kinetic analysis; Al-Mg alloy; Rare earth erbium |
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The hot deformation behavior of an Al-5.7 wt.%Mg alloy with erbium has been investigated. Compression tests are performed in the temperature range of 300-500 °C and in the strain rate ranging from 0.001 s-1 to 50 s-1 up to a true strain of 0.7. The processing maps are developed at different strains and the standard kinetic analysis has been applied to evaluate the rate controlling mechanisms. The processing maps have exhibited two domains of 350-450 °C at 0.001-0.03 s-1 and 450-500 °C at 0.01-1 s-1, representing dynamic recovery of Al-5.7 wt.%Mg with erbium. The apparent activation energies estimated in these two domains are 180 kJ/mol and 163 kJ/mol respectively, which suggests that cross-slip of dislocation and lattice self-diffusion are the deformation mechanisms. At strain rates higher than 10 s-1, the flow curves demonstrate flow softening behavior, and the flow instability regions reveal mixed microstructure of local deformation and dynamic recrystallization. |
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0921-5093 |
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NU @ karnesky @ |
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10600 |
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Gang, Meng; bolong, Li; hongmei, Li; hui, Huang; zuoren, Nie |
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Hot deformation behavior of an Al-5.7 wt.%Mg alloy with erbium |
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Journal Article |
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2009 |
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Materials Science and Engineering: A |
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516 |
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1-2 |
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131-137 |
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Aluminum alloy with erbium; Drv; Hot deformation; Microstructure; Zener-Hollomon parameter |
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The hot deformation behavior of an Al–5.7 wt.%Mg alloy with erbium was studied by compressive deformation tests in the strain rate range of 0.001–10 s−1 and temperature range of 300–500 °C. The constitutive equations were presented considering the values of A and β as a function of strain in the exponential function form. The error of predicted and measured data was less than 9%. Dynamic recrystallization was restrained by precipitate with Er and dynamic recovery dominated in the hot deformation. The mechanism of dynamic recovery was dislocation movement and the development of microstructure during deformation can be characterized by the Z parameter, and then the relationship between subgrains and deformation parameters have been also established. |
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0921-5093 |
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The hot deformation behavior of an Al-5.7�wt.%Mg alloy with erbium was studied by compressive deformation tests in the strain rate range of 0.001-10�s-1 and temperature range of 300-500��C. The constitutive equations were presented considering the values of A and [beta] as a function of strain in the exponential function form. The error of predicted and measured data was less than 9%. Dynamic recrystallization was restrained by precipitate with Er and dynamic recovery dominated in the hot deformation. The mechanism of dynamic recovery was dislocation movement and the development of microstructure during deformation can be characterized by the Z parameter, and then the relationship between subgrains and deformation parameters have been also established. |
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NU @ karnesky @ 18273 |
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10646 |
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Lin, Shuangping; Nie, Zuoren; Huang, Hui; Li, Bolong |
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Annealing behavior of a modified 5083 aluminum alloy |
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Journal Article |
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2010 |
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Materials & Design |
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31 |
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3 |
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1607-1612 |
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The annealing behavior of a modified 5083 aluminum alloy was studied in the temperature range of 125-375 °C with different holding times. The results shown that the annealing temperature was more sensitive to the mechanical and corrosion resistance properties compared with the annealing holding time. The mechanical and corrosion resistance properties depend on annealing treatment due to different dislocation configuration in the matrix and the second phase interface, annealing temperature and time have been optimized for both of those properties improvement. |
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0261-3069 |
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NU @ karnesky @ |
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10727 |
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Rupert, Timothy J.; Trenkle, Jonathan C.; Schuh, Christopher A. |
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Enhanced solid solution effects on the strength of nanocrystalline alloys |
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Journal Article |
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2011 |
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Acta Materialia |
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59 |
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4 |
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1619-1631 |
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Solute strengthening; Nanocrystalline metals; Mechanical behavior; Nanoindentation; Thin films |
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Solid solution strengthening in nanocrystalline alloys is studied using sputtered Ni-W as a model system. In the composition range of 0-20 at.% W, the sputtered alloys have a nanocrystalline structure with a grain size that is independent of composition. Nanoindentation of these alloys shows that solute addition increases strength to very high levels, almost in proportion to the solute content. This behavior is not expected based on traditional solid solution strengthening mechanistic models of local dislocation pinning at solute atoms, but can be explained by further considering a global effect of solute on the average properties of the Ni lattice. The new strengthening term arises by considering grain boundaries as pinning points for dislocation motion in nanocrystalline materials and incorporating the effect of solutes on such a mechanism. Our discussion surrounding Ni-W also provides insights into other solid solution nanocrystalline systems, a variety of which we show can be accurately described using the same concept. These developments also explain the origin of solid solution softening in some nanocrystalline alloys. |
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1359-6454 |
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NU @ karnesky @ |
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11000 |
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Blobaum, K.J.M.; Krenn, C.R.; Wall, M.A.; Massalski, T.B.; Schwartz, A.J. |
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Nucleation and growth of the [alpha]' martensitic phase in Pu-Ga alloys |
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Journal Article |
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2006 |
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Acta Materialia |
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Acta Mater. |
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54 |
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15 |
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4001-4011 |
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Phase transformations; Martensitic phase transformation; Nucleation of phase transformations |
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In a Pu-2.0 at.% Ga alloy, it is observed experimentally that the amount of the martensitic [alpha]' product formed upon cooling the metastable [delta] phase below the martensite burst temperature (Mb) is a function of the holding temperature and holding time of a prior conditioning ("annealing") treatment. Before subjecting a sample to a cooling and heating cycle to form and revert the [alpha]' phase, it was first homogenized for 8 h at 375 [degree sign]C to remove any microstructural memory of prior transformations. Subsequently, conditioning was carried out in a differential scanning calorimeter apparatus at temperatures in the range between -50 and 370 [degree sign]C for periods of up to 70 h to determine the holding time and temperature that produced the largest volume fraction of [alpha]' upon subsequent cooling. Using transformation peak areas (i.e., the heats of transformation) as a measure of the amount of [alpha]' formed, the largest amount of [alpha]' was obtained following holding at 25 [degree sign]C for at least 6 h. Additional time at 25 [degree sign]C, up to 70 h, did not increase the amount of subsequent [alpha]' formation. At 25 [degree sign]C, the Pu-2.0 at.% Ga alloy is below the eutectoid transformation temperature in the phase diagram and the expected equilibrium phases are [alpha] and Pu3Ga, although a complete eutectoid decomposition of [delta] to these phases is expected to be extremely slow. It is proposed here that the influence of the conditioning treatment can be attributed to the activation of [alpha]-phase embryos in the matrix as a beginning step toward the eutectoid decomposition, and we discuss the effects of spontaneous self-irradiation accompanying the Pu radioactive decay on the activation process. Subsequently, upon cooling, certain embryos appear to be active as sites for the burst growth of martensitic [alpha]' particles, and their amount, distribution, and potency appear to contribute to the total amount of martensitic product formed. A modeling approach based on classic nucleation theory is presented to describe the formation of [alpha]-phase embryos during conditioning. The reasons why the holding times during conditioning become eventually ineffective in promoting more [alpha]' formation on cooling are discussed in terms of the differences in the potency of the embryos created in the [delta] matrix during conditioning and in terms of growth-impeding volume strains in the matrix resulting from an increasing number of martensite particles, thus opposing further growth. It is suggested that the disparate amounts of the [alpha]' formation reported in the literature following various studies may be in part a consequence of the fact that conditioning times at ambient temperatures are inevitably involved in any handling of radioactive samples prior to testing. |
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NU @ karnesky @ |
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1916 |
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Vurpillot, F.; Renaud, L.; Blavette, D. |
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A New Step Towards the Lattice Reconstruction in 3DAP |
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Journal Article |
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2003 |
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Ultramicroscopy |
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95 |
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223-229 |
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TY - JOUR |
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refbase @ user |
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1677 |
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Deconihout, B.; Renaud, L.; Da Costa, G.; Bouet, M.; Bostel, A.; Blavette, D. |
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Implementation of an Optical {TAP}: Preliminary Results |
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Journal Article |
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1998 |
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Ultramicroscopy |
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73 |
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1-4 |
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253-260 |
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The FIM Group of the University of Rouen is developing a new type of detector that can be used in atom probe and 3D atom probe applications. This detector consists of an array of conductive and transparent strips covered with a phosphorescent material. After having produced light, electrons generated by ionic impacts onto microchannel plates produce signals on strips that are used for timing. At the same time, light produced by ions on the phosphor screen is recorded by means of a CCD image sensor. Then, the comparison between positions and the distribution of time of flight on the strip array makes it possible to correlate positions and times for each event. In this contribution, preliminary results obtained with a 5 x 5 cm2 detector having eight strips will be shown. Potential capabilities and performance will be discussed. |
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TY - JOUR |
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refbase @ user |
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1056 |
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