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Knipling, Keith E.; Karnesky, Richard A.; Lee, Constance P.; Dunand, David C.; Seidman, David N. |
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Publication |
Precipitation Evolution in Al-0.1Sc, Al-0.1Zr, and Al-0.1Sc-0.1Zr (at.%) Alloys during Isochronal Aging |
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Journal Article |
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2010 |
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Abstract |
Acta Materialia |
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58 |
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15 |
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Summary Language |
5184-5195 |
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Aluminum alloys, Precipitation, Scandium, Zirconium, Atom-probe tomography; Al-Sc-Zr |
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Abbreviated Series Title |
Precipitation strengthening is investigated in binary Al-0.1Sc, Al-0.1Zr, and ternary Al-0.1Sc-0.1Zr (at.%) alloys aged isochronally between 200 and 600 °C. A pronounced synergistic effect is observed when both Sc and Zr are present. Above 325 °C, where peak microhardness (670 MPa) occurs in the binary Al-Sc alloy due to Al3Sc (L12) nanometer-scale precipitates, Zr additions result in a secondary increase in strength due to additional precipitation of Zr-enriched outer shells onto these precipitates. The ternary alloy reaches a peak microhardness of 780 MPa at 400 °C, delaying overaging by >100 °C compared with the binary Al-Sc alloy and increasing strength compared with the binary Al-Zr alloy (peak microhardness of 420 MPa at 425–450 °C). Compositions, radii, volume fractions, and number densities of the Al3(Sc1-xZrx) precipitates are measured directly using atom-probe tomography. This information is used to quantify the observed strengthening increments, attributed to dislocation shearing of the Al3(Sc1-xZrx) precipitates. |
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NU @ karnesky @ |
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10705 |
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Hadley, K. W.; Donders, P. J.; Lee, M. J. G. |
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Influence of shank profile on laser heating of a field emitter |
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1984 |
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Journal of Applied Physics |
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J. Appl. Phys. |
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8559 |
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Venus, D.; Lee, M. J. G. |
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Sample positioner and deflection energy analyzer for measurements of photofield emission |
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1985 |
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Review of Scientific Instruments |
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Rev. Sci. Instrum. |
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8837 |
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Kim, Jeong Kil; Kim, Yeong Ho; Lee, Bong Ho; Kim, Kyoo Young |
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New findings on intergranular corrosion mechanism of stabilized stainless steels |
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Journal Article |
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2011 |
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Electrochimica Acta |
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ADVANCES IN CORROSION SCIENCE FOR LIFETIME PREDICTION AND SUSTAINABILITYSelection of papers from the |
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56 |
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4 |
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1701-1710 |
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Intergranular corrosion; Stainless steel; Stabilizer effect; Segregation; Chromium |
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Number of different sets of stabilized both ferritic and austenitic stainless steels with various alloying elements were evaluated to verify new findings on the intergranular corrosion mechanism. The intergranular segregation and precipitation were analyzed by using a transmission electron microscopy with an energy dispersive X-ray spectroscopy and a laser assisted three-dimensional atom probe. On the basis of the current result, it is newly proposed that the intergranular corrosion occurring in the stabilized both ferritic and austenitic stainless steels is induced by Cr-depletion due to segregation of un-reacted Cr atoms around carbides of stabilizer elements (Ti or Nb) along the grain boundary, but not due to formation of Cr-carbide. A prevention method for this type of intergranular corrosion is also suggested after critical evaluation on the effect of Cr, C, and Ni. |
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0013-4686 |
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NU @ karnesky @ |
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11057 |
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Vaynman, S.; Fine, M.E.; Lee, S.; Espinosa, H.D. |
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Effect of strain rate and temperature on mechanical properties and fracture mode of high strength precipitation hardened ferritic steels |
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Journal Article |
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2006 |
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Scripta Materialia |
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55 |
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4 |
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351-354 |
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Steel; Fracture; Strain rate effect |
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NU @ p-kolli @ |
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9683 |
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Jiang, C.; Gleeson, B. |
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Effects of Cr on the elastic properties of B2 NiAl: A first-principles study |
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Journal Article |
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2006 |
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Scripta Materialia |
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55 |
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9 |
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759-762 |
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Chromium; Nickel aluminides; Point defects; First-principle electron theory |
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We performed first-principles calculations based on the density functional theory to investigate the effects of Cr addition on the elastic properties of B2 NiAl. The Wagner-Schottky model was employed to correlate single-crystal elastic constants of ternary B2 NiAl-Cr alloys with point defect concentrations, in which the defect-formation parameters were obtained from first-principles supercell calculations. The present calculations clearly show that the effects of Cr addition on the elastic properties of B2 NiAl are strongly composition-dependent. |
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NU @ p-kolli @ |
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9710 |
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Lee, Byeong-Joo; Jang, Je-Wook |
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A modified embedded-atom method interatomic potential for the Fe–H system |
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Journal Article |
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2007 |
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Acta Materialia |
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55 |
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20 |
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6779-6788 |
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Modified embedded-atom method; Iron–hydrogen alloys; Atomistic simulation; Molecular dynamics; Lattice defect |
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A modified embedded-atom method (MEAM) interatomic potential for the Fe–H binary system has been developed using previously developed MEAM potentials of Fe and H. The potential parameters were determined by fitting to experimental data on the dilute heat of solution of hydrogen in body-centered cubic (bcc) and face-centered cubic (fcc) Fe, the vacancy–hydrogen binding energy in bcc Fe, and to a first-principles calculation for the lattice parameter and bulk modulus of a hypothetical NaCl-type FeH. The potential accurately reproduces the known physical properties of hydrogen as an interstitial solute element in bcc and fcc Fe. The applicability of the potential to atomistic approaches for investigating interactions between hydrogen atoms and other defects such as vacancies, dislocations and grain boundaries, and also for investigating the effects of hydrogen on various deformation and mechanical behaviors of iron is demonstrated. |
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1359-6454 |
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NU @ karnesky @ |
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11399 |
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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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NU @ karnesky @ |
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653 |
| Permanent link to this record |
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Jiang, C.; Sordelet, D.J.; Gleeson, B. |
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Effects of Pt on the elastic properties of B2 NiAl: A combined first-principles and experimental study |
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Journal Article |
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2006 |
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Acta Materialia |
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54 |
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9 |
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2361-2369 |
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Platinum; Nickel aluminides; Point defects; First-principles electron theory |
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First-principles calculations were performed to investigate the effects of Pt addition on the elastic properties of B2 NiAl. By correlating single-crystal elastic constants with point defect concentrations in the context of the Wagner-Schottky model, a general equation is proposed to calculate elastic properties of ternary B2 NiAl-Pt alloys as a function of alloy composition, in which the defect formation parameters were obtained from first-principles supercell calculations. At constant Al content, the calculations showed that the addition of Pt to B2 NiAl will increase its bulk modulus B but decrease both its shear moduli C' and C44. Results from the model calculations were found to be in good agreement with experimental measurements on polycrystalline samples, as well as direct first-principles calculations on special quasirandom structures. |
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NU @ p-kolli @ |
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9711 |
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Kwon, H.; Barlat, F.; Lee, M.; Chung, Y.; Uhm, S. |
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Influence of Tempering Temperature on Low Cycle Fatigue of High Strength Steel |
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Journal Article |
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2014 |
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ISIJ International |
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54 |
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4 |
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979-984 |
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In this study, the mechanical and low cycle fatigue properties for a heat-treatment steel subjected to quenching and tempering (QT) were evaluated. The steel had a modified chemical composition with respect to a conventional material and was subjected to tempering at various temperatures. It was shown that the material tempered at 250°C exhibited superior fatigue properties in the short life regions. Carbon atom clusters in concentration of 18 at% in martensite were observed using atom probe tomography (APT) for the steel tempered at 250°C. It is believed that these clusters contribute to the improvement of fatigue properties by hindering the motion of dislocations. |
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NU @ karnesky @ |
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11486 |
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