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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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Abstract |
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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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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Tewari, S.N.; Vijayakumar, M.; Lee, J.E.; Curreri, P.A. |
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Solutal partition coefficients in nickel-based superalloy PWA-1480 |
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Journal Article |
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1991 |
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Materials Science and Engineering A |
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141 |
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1 |
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97-102 |
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Solutal profiles in dendritic single-crystal specimens of PWA-1480 nickel-base superalloy, which were directionally solidified and quenched, were examined on several transverse cross-sections to obtain the partition coefficients. Similar to their nickel-base binaries, the partition coefficients of tantalum, titanium, and aluminum were found to be less than unity; those of tungsten and cobalt were greater than unity. The partition coefficients were temperature independent in the range 1584-1608 K. The contribution of solid-state diffusion to microsegregation was observed to be negligible. |
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NU @ karnesky @ |
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9820 |
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Lee, W.-B.; Hong, S.-G.; Park, C.-G.; Park, S.-H. |
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Carbide precipitation and high-temperature strength of hot-rolled high-strength, low-alloy steels containing Nb and Mo |
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Journal Article |
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2002 |
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Metallurgical and Materials Transactions A |
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33 |
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6 |
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1689-1698 |
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Abstract The effects of a Mo addition on both the precipitation kinetics and high-temperature strength of a Nb carbide have been investigated in the hot-rolled high-strength, low-alloy (HSLA) steels containing both Nb and Mo. These steels were fabricated by four-pass hot rolling and coiling at 650C, 600C, and 550C. Microstructural analysis of the carbides has been performed using field-emission gun transmission electron microscopy (TEM) employing energy-dispersive X-ray spectroscopy (EDS). The steels containing both Nb and Mo exhibited a higher strength at high temperatures (∼600 C) in comparison to the steel containing only Nb. The addition of Mo increased the hardenability and led to the refinement of the bainitic microstructure. The proportion of the bainitic phase increased with the increase of Mo content. The TEM observations revealed that the steels containing both Nb and Mo exhibited fine (<10 nm) and uniformly distributed metal carbide (MC)-type carbides, while the carbides were coarse and sparsely distributed in the steels containing Nb only. The EDS analysis also indicated that the fine MC carbides contain both Nb and Mo, and the ratio of Mo/Nb was higher in the finer carbides. In addition, electron diffraction analysis revealed that most of the MC carbides had one variant of the B-N relationship ((100)MC//(100)ferrite, [011]MC//[010]ferrite) with the matrix, suggesting that they were formed in the ferrite region. That is, the addition of Mo increased the nucleation sites of MC carbides in addition to the bainitic transformation, which resulted in finer and denser MC carbides. It is, thus, believed that the enhanced high-temperature strength of the steels containing both Nb and Mo was attributed to both bainitic transformation hardening and the precipitation hardening caused by uniform distribution of fine MC particles. |
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NU @ p-kolli @ |
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9838 |
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Lee, B.C.; Park, J.K. |
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Effect of the addition of Ag on the strengthening of Al3Li phase in Al-Li single crystals |
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Journal Article |
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1998 |
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Acta Materialia |
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46 |
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12 |
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4181-4187 |
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The variation of the critical resolved shear stress as a function of aging condition has been measured in ternary Al-~(1.9-2.0) wt% Li-~0.4 wt% Ag single crystals and has been analyzed using the same version of order-hardening theory as in our previous work in binary single crystals. The result showed that the antiphase boundary energy of the Al3Li lattice on {111} definitively increases from about 0.118 J/m2 in binary crystals to 0.128+/-0.012 J/m2 in ternary crystals, in good agreement with the analysis of the transition behavior from shearing to looping and of the dislocation pair spacings. A strong segregation tendency of Ag into the Al3Li lattice is believed to be responsible for this increment. Our previous result of [gamma]apb (0.118+/-0.006 J/m2) in binary crystals is, although unlikely from the recent suggestion of Nembach, the best value one can obtain from the recent knowledge of order-hardening theory. This is slightly larger than that (about 0.100 J/m2) obtained from the analysis of the transition from shearing to looping and somewhat larger than the result (about 0.085 J/m2) of the first-principles calculation. Three factors are discussed as principal causes of a possibility of an overestimation of [gamma]apb on applying order-hardening theory. |
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NU @ karnesky @ |
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9941 |
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Kim, Y.-C.; Adusumilli, P.; Lauhon, L.J.; Seidman, D.N.; Jung, S.-Y.; Lee, H.-D.; Alvis, R.L.; Ulfig, R.M.; Olson, J.D. |
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Three-dimensional atomic-scale mapping of Pd in Ni[sub:1 - x]Pd[sub:x]Si/Si(100) thin films |
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Journal Article |
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2007 |
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Applied Physics Letters |
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Appl. Phys. Lett. |
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91 |
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11 |
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113106:1-3 |
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annealing; interface roughness; nickel compounds; palladium compounds; rapid thermal processing; semiconductor-metal boundaries |
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Atom-probe tomography was utilized to map the three-dimensional distribution of Pd atoms in nickel monosilicide thin films on Si(100). A solid-solution Ni0.95Pd0.05 film on a Si(100) substrate was subjected to rapid thermal processing plus steady-state annealing to simulate the thermal processing experienced by NiSi source and drain contacts in standard complementary metal-oxide-semiconductor processes. Pd is found to segregate at the (Ni0.95Pd0.05)Si/Si(100) heterophase interface, which may provide a previously unrecognized contribution to monosilicide stabilization. The silicide-Si heterophase interface was reconstructed in three dimensions on an atomic scale and its chemical roughness was evaluated. |
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Aip |
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NU @ karnesky @ |
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9944 |
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Galtrey, M.J.; Oliver, R.A.; Kappers, M.J.; McAleese, C.; Zhu, D.; Humphreys, C.J.; Clifton, P.H.; Larson, D.; Cerezo, A. |
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Compositional inhomogeneity of a high-efficiency In[sub x]Ga[sub 1 - x]N based multiple quantum well ultraviolet emitter studied by three dimensional atom probe |
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Journal Article |
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2008 |
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Applied Physics Letters |
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Appl. Phys. Lett. |
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92 |
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4 |
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041904-3 |
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III-V semiconductors; indium compounds; light emitting diodes; semiconductor quantum wells; wide band gap semiconductors |
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An InxGa1−xN based multiple quantum well structure emitting in the ultraviolet, which has the highest reported efficiency (67%) at its wavelength (380 nm), was analyzed with the three-dimensional atom probe. The results reveal gross discontinuities and compositional variations within the quantum well layers on a 20–100 nm length scale. In addition, the analysis shows the presence of indium in the AlyGa1−yN barrier layers, albeit at a very low level. By comparing with analogous epilayer samples, we suggest that the quantum well discontinuities we observe may play an important role in improving the efficiency of these structures. |
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NU @ karnesky @ |
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10199 |
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Radmilovic, V.; Tolley, A.; Marquis, E.A.; Rossell, M.D.; Lee, Z.; Dahmen, U. |
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Monodisperse Al3(LiScZr) core/shell precipitates in Al alloys |
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Journal Article |
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2008 |
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Scripta Materialia |
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58 |
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7 |
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529-532 |
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Al alloy; Atom probe tomography (APT); Core/shell precipitates; Dispersion strengthening; Electron microscopy |
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We demonstrate a way of producing monodisperse Al3(LiScZr) core/shell inclusions using solid-state reactions. A uniform distribution of particles with a Li- and Sc-rich core surrounded by Li-rich shell a few nanometers thick with Zr segregating at the core/shell interface can be made reproducibly by exploiting kinetic and thermodynamic parameters. This approach to generating precipitate distributions can be applied to a range of alloys and could lead to new types of dispersion-strengthened materials. |
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NU @ karnesky @ 13381 |
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10202 |
| Permanent link to this record |
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Lee, S.-M.; Pyun, S.-I. |
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Effects of hydrogen redistribution on hydrogen-assisted cracking in Al-1.9% Li and Al-4.5% Zn-2.3% Mg alloys |
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Journal Article |
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1990 |
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Scripta Metallurgica et Materialia |
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24 |
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9 |
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1629-1634 |
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NU @ karnesky @ |
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10238 |
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