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Han, S. Z.; Rho, B. S.; Lee, H. M.; Choi, S. K. |
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Effect of Alloyed Ti:Zr ratio on Phase Stability of Al$_{66}$Mn$_9$(Ti,Zr)$_{25}$ Intermetallic Compounds |
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Journal Article |
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1996 |
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Abstract  |
Intermetallics |
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4 |
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3 |
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Summary Language |
245-249 |
Series Editor |
hardness
phase stability
compositional variation effects
zirconium trialuminides
l12 compounds
cubic phases
al3ti
deformation
behavior
do22
al66ti25mn9
strength
systems |
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Abbreviated Series Title |
The tetragonal Al-3(Ti1-xZrx) phase is transformed by the addition of 9% Mn to the cubic L1(2)-type Al66Mn9(Ti1-xZrx)(25) with a small amount of second phases such as Al8Mn5 and Al2Zr still existing in the as-cast condition. Second phases disappear when intermetallic compounds are homogenized at 1000 degrees C for 24 h, and alloys are of the monolithic L1(2) phase with compositional variations still existent. The combined addition of Ti and Zr is found to reduce the hardness of intermetallic alloys compared to the addition of Ti or Zr alone. The Al66Mn9(Ti, Zr)(25) phase is found to be structurally stable but compositionally unstable. |
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Korea Adv Inst Sci & Technol,Dept Mat Sci & Engn,Taejon 305701,South Korea |
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Times Cited: 3
Article
English
Cited References Count: 22
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refbase @ user |
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1171 |
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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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0370-1972 |
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ISI:000256242300017 |
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NU @ m-krug @ |
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10392 |
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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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1998 |
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Acta Materialia |
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46 |
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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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Lee, Woei-Shyan; Chen, Tao-Hsing; Lin, Chi-Feng; Chen, Ming-Shiang |
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Impact deformation behaviour and dislocation substructure of Al-Sc alloy |
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Journal Article |
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2010 |
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Journal of Alloys and Compounds |
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493 |
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1-2 |
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580-589 |
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Al-Sc alloy; Strain rate sensitivity; Activation volume; Adiabatic shear band; Dislocation; Precipitates |
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This paper employs a compressive split-Hopkinson pressure bar to investigate the impact deformation behaviour of Al-Sc alloy under high strain rates of 1.2103s-1, 3.2103s-1 and 5.8103s-1, respectively, and temperatures of -100C, 25C and 300C. It is shown that for a constant temperature, the flow stress, work hardening rate and strain rate sensitivity increase with increasing strain rate, while the activation volume decreases. Conversely, for a constant strain rate, the flow stress, work hardening rate and strain rate sensitivity decrease with increasing temperature, while the activation volume increases. It is found that the impact deformation behaviour of Al-Sc alloy can be accurately described using the Zerilli-Armstrong constitutive equation. Optical microscopy (OM) observations reveal that the specimens fail principally as the result of an adiabatic shearing mechanism. Furthermore, scanning electron microscopy (SEM) observations show that the fracture surfaces are characterised by a dimple-like structure, which indicates a ductile failure mode. Transmission electron microscopy (TEM) observations indicate that the dislocation density and cell size are related to the strain rate, flow stress and temperature. Finally, the TEM observations suggest that the strengthening effect observed in the deformed Al-Sc alloy is the result of Al3Sc precipitates within the matrix and at the grain boundaries, which suppress dislocation motion and prompt an increase in the work hardening stress. |
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0925-8388 |
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NU @ karnesky @ |
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10784 |
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Lee, W.-S.; Chen, T.-H. |
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Mechanical and microstructural response of aluminum-scandium (Al-Sc) alloy as a function of strain rate and temperature |
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Journal Article |
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2009 |
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Materials Chemistry and Physics |
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113 |
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2-3 |
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734-745 |
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Al-Sc alloy; Strain rate sensitivity; Activation energy; Shearing; Dislocation; Precipitates |
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This study applies a compressive split Hopkinson bar to investigate the mechanical response, microstructural evolution and fracture characteristics of aluminum-scandium (Al-Sc) alloy at temperatures ranging from -100 °C to 300 °C and strain rates of 1.2 × 103 s-1, 3.2 × 103 s-1 and 5.8 × 103 s-1. The relationship between the dynamic mechanical behaviour of the Al-Sc alloy and its microstructural characteristics is explored. The fracture features and microstructural evolution are observed using scanning and transmission electron microscopy techniques. The stress-strain relationships indicate that the flow stress, work hardening rate and strain rate sensitivity increase with strain rate, but decrease with increasing temperature. Conversely, the activation volume and activation energy increase as the temperature increases or the strain rate decreases. Additionally, the fracture strain reduces with increasing strain rate and decreasing temperature. However, at room temperature under a low strain rate of 1.2 × 103 s-1 and at a high experimental temperature of 300 °C under all three tested strain rates, the specimens do not fracture, even under large strain deformations. The Zerilli-Armstrong fcc constitutive model is used to describe the plastic deformation behaviour of the Al-Sc alloy. Comparing the predicted flow stress values with the experimental values over all the considered strain rate and temperature conditions, the maximum error between the two sets of results is found to be less than 4%. SEM observations show that the specimens fracture predominantly as a result of a shearing mechanism. Moreover, the surfaces of the fractured specimens are characterised by transgranular dimpled features, which are indicative of a ductile fracture mode. Fine Al3Sc precipitates are found to be distributed in the matrix and at the grain boundaries. Finally, the TEM analysis results reveal that the dislocation density increases, but the dislocation cell size decreases, with increasing strain rate. However, a higher temperature causes the dislocation density to decrease, thereby increasing the dislocation cell size. |
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NU @ karnesky @ |
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10512 |
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Huang, L.; Lee, Y. H. |
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Experimental method for preparing nanometer scale Pd probe |
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Journal Article |
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1993 |
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Review of Scientific Instruments |
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Rev. Sci. Instrum. |
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64 |
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10 |
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3022-3023 |
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Two-step electrochemical etching is used to fabricate a palladium microprobe having a tip diameter less than 20 nm. The first etching is done at 4–7 V in a solution containing 4:6 volume ratio of HCl:HNO3, while in the second the etching, low voltage pulses are used. |
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no |
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5327 |
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Darling, K.A.; VanLeeuwen, B.K.; Semones, J.E.; Koch, C.C.; Scattergood, R.O.; Kecskes, L.J.; Mathaudhu, S.N. |
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Stabilized Nanocrystalline Iron-based Alloys: Guiding Efforts in Alloy Selection |
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Journal Article |
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2011 |
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Materials Science and Engineering: A |
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In Press |
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Accepted Manuscript |
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Mechanical Alloying; Grain Growth; Interfaces; Recrystallization and Nanostructured Materials |
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Using a modified regular solution model for grain boundary solute segregation, the relative thermal stability of a number of Fe-based nanocrystalline binary alloys was predicted with considerable accuracy. It was found that nanocrystalline iron was strongly stabilized by zirconium, moderately stabilized by tantalum, and not significantly stabilized by nickel or chromium. These findings are fully in line with the aforementioned predictions. This success with iron based alloys highlights the utility of this practical approach to selecting stabilizing solutes for nanocrystalline alloys. |
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0921-5093 |
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no |
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NU @ karnesky @ |
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11038 |
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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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no |
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NU @ karnesky @ 13381 |
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10202 |
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Tomaszewska, Agnieszka; Shim, Hyungjoon; Ahn, Chanmo; Lee, Geunseop |
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Reinvestigation of the alkali-metal-induced Ge(1 1 1)3×1 reconstruction on the basis of boundary structure observations |
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Journal Article |
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2011 |
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Ultramicroscopy |
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Special Issue: 52nd International Field Emission Symposium |
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111 |
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6 |
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392-396 |
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Alkali-metal adsorption; Ge(1 1 1); Surface reconstruction; HCC model; Stm |
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We have investigated the surface atomic structure of boundary area of Li- and Na-induced Ge(1 1 1)3×1 reconstruction using scanning tunneling microscope. On Li/Ge(1 1 1)3×1, the 3×1 phase was found to be terminated with a single row in the filled-state image and with dimer-like features in the empty-state image. The images of both interior and boundary of the Li/Ge(1 1 1)3×1 surface are compatible with the honeycomb-chain-channel (HCC) model, which has substrate atoms with double bonds and is well established as the structure of AM/Si(1 1 1)3×1 surfaces. In contrast, termination with zigzag double rows at the domain boundary edges was observed in the filled-state images of the Na/Ge(1 1 1)3×1 phase, which is not reconcilable with the HCC structure. The filled-state STM feature of the boundary region of the Na/Ge(1 1 1)3×1 phase supports a structural model not having Ge=Ge double bonds, which was proposed to interpret its empty-state images. The trend of bondings between atoms in the surface layer of the AM-induced 3×1 reconstruction of Si and Ge is discussed in terms of electronegativity differences. |
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0304-3991 |
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no |
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NU @ karnesky @ |
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11195 |
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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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no |
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NU @ p-kolli @ |
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9710 |
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