| |
Records |
Links |
|
Type |
Lee, S.-M.; Pyun, S.-I. |
| |
Publication |
Effects of hydrogen redistribution on hydrogen-assisted cracking in Al-1.9% Li and Al-4.5% Zn-2.3% Mg alloys |
Volume |
Journal Article |
Pages |
1990 |
| |
Abstract |
Scripta Metallurgica et Materialia |
|
| |
Corporate Author |
|
|
Publisher |
24 |
|
Editor |
9 |
| |
Summary Language |
1629-1634 |
Series Editor  |
|
|
Abbreviated Series Title |
|
| |
Series Issue |
|
ISSN |
|
|
Medium |
|
| |
Expedition |
|
Notes |
|
|
Call Number |
|
|
Contribution Id |
|
|
Serial |
|
URL |
|
ISBN |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
no |
|
NU @ karnesky @ |
|
10238 |
| Permanent link to this record |
| |
|
| |
|
Lee, D.-H.; Hong, K.T.; Nam, S.W. |
|
Intergraular fracture behavior of an Al-3at.%Mg solid solution alloy under the viscous glide creep condition |
|
Journal Article |
|
1991 |
|
Scripta Metallurgica et Materialia |
|
|
|
25 |
|
4 |
|
823-828 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
no |
|
NU @ karnesky @ |
|
10279 |
| Permanent link to this record |
| |
|
| |
|
Lee, Z.; Witkin, D.B.; Radmilovic, V.; Lavernia, E.J.; Nutt, S.R. |
|
Bimodal microstructure and deformation of cryomilled bulk nanocrystalline Al-7.5Mg alloy |
|
Journal Article |
|
2005 |
|
Materials Science and Engineering: A |
|
The Langdon Symposium: Flow and forming of Crystalline Materials |
|
410-411 |
|
|
|
462-467 |
|
Nanocrystalline; Bimodal; Cryomilling; Aluminum; Deformation |
|
The microstructure, mechanical properties and deformation response of bimodal structured nanocrystalline Al-7.5Mg alloy were investigated. Grain refinement was achieved by cryomilling of atomized Al-7.5Mg powders, and then cryomilled nanocrystalline powders blended with 15 and 30% unmilled coarse-grained powders were consolidated by hot isostatic pressing followed by extrusion to produce bulk nanocrystalline alloys. Bimodal bulk nanocrystalline Al-7.5Mg alloys, which were comprised of nanocrystalline grains separated by coarse-grain regions, show balanced mechanical properties of enhanced yield and ultimate strength and reasonable ductility and toughness compared to comparable conventional alloys and nanocrystalline metals. The investigation of tensile and hardness test suggests unusual deformation mechanisms and interactions between ductile coarse-grain bands and nanocrystalline regions. |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
no |
|
NU @ karnesky @ |
|
10321 |
| Permanent link to this record |
| |
|
| |
|
Witkin, D.; Lee, Z.; Rodriguez, R.; Nutt, S.; Lavernia, E. |
|
Al-Mg alloy engineered with bimodal grain size for high strength and increased ductility |
|
Journal Article |
|
2003 |
|
Scripta Materialia |
|
|
|
49 |
|
4 |
|
297-302 |
|
Aluminum alloys; Nanocrystalline materials; Mechanical properties |
|
Al-7.5Mg powders were cryomilled, then consolidated and extruded to produce bulk nanostructured material. The extrusions had a tensile yield strength of 641 MPa and an ultimate strength of 847 MPa. Additional samples were prepared by combining cryomilled powder unmilled Al-7.5Mg, resulting in extrusions with high strength and increased ductility. |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
no |
|
NU @ karnesky @ |
|
10322 |
| Permanent link to this record |
| |
|
| |
|
Ye, J.; Han, B.Q.; Lee, Z.; Ahn, B.; Nutt, S.R.; Schoenung, J.M. |
|
A tri-modal aluminum based composite with super-high strength |
|
Journal Article |
|
2005 |
|
Scripta Materialia |
|
|
|
53 |
|
5 |
|
481-486 |
|
Metal matrix composites; Aluminum alloy; Cryomilling; Compression test; Nanocrystalline |
|
A bulk composite with 10 wt.% B4C, 50 wt.% coarse-grained 5083 Al and the balance nanocrystalline 5083 Al was fabricated, using cryomilling and compaction. This tri-modal composite exhibited an extremely high yield strength (up to 1065 MPa) when tested under compressive load. The structure-property relationships are discussed. |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
no |
|
NU @ karnesky @ |
|
10328 |
| Permanent link to this record |
| |
|
| |
|
Veerababu, R.; Balamuralikrishnan, R.; Muraleedharan, K.; Srinivas, M. |
|
Three-dimensional atom probe investigation of microstructural evolution during tempering of an ultra-high-strength high-toughness steel |
|
Journal Article |
|
2008 |
|
Metallurgical And Materials Transactions A-Physical Metallurgy And Materials Science |
|
Metall. Mater. Trans. A-Phys. Metall. Mater. Sci. |
|
39a |
|
7 |
|
1486-1495 |
|
|
|
The evaluation of the tempering response of an ultra-high-strength, high-toughness (UHSHT) steel revealed that samples austenitized at 900 degrees C and tempered for 4 and 8 hours at 485 degrees C had similar yield strengths but a similar to 50 pct increase in fracture toughness for the 8-hour temper. The results of our investigations of microstructural origins of this difference, using the nanometric scale resolution of the three-dimensional atom probe (3DAP) suggest that nanoscale strengthening precipitates, essentially carbides and intermetallic clusters (containing primarily Cr and Mo atoms), are present in both samples. The chemical compositions of the particles in the two samples were found to be similar, but clear evidence of differences in physical attributes of the precipitates, such as particle size, morphology, and interparticle spacing, are seen. |
|
Def Met Res Lab, Hyderabad 500058, Andhra Pradesh, India, Email: muraleek@hotmail.com |
|
|
|
|
|
Springer |
|
|
|
|
|
English |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
1073-5623 |
|
|
|
|
|
|
|
|
|
|
|
ISI:000256081500004 |
|
no |
|
NU @ m-krug @ |
|
10377 |
| Permanent link to this record |
| |
|
| |
|
Galtrey, M.J.; Oliver, R.A.; Kappers, M.J.; McAleese, C.; Zhu, D.; Humphreys, C.J.; Clifton, P.H.; Larsen, D.; Cerezo, A. |
|
Atom probe revels the structure of InxGe1-xN based quantum wells in three dimensions |
|
Journal Article |
|
2008 |
|
Physica Status Solidi B-Basic Solid State Physics |
|
Phys. Status Solidi B-Basic Solid State Phys. |
|
245 |
|
5 |
|
861-867 |
|
|
|
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. |
|
Univ Cambridge, Dept Mat Sci & Met, Cambridge CB2 3QZ, England, Email: mjg73@cam.ac.uk |
|
|
|
|
|
Wiley-V C H Verlag Gmbh |
|
|
|
|
|
English |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
0370-1972 |
|
|
|
|
|
|
|
|
|
|
|
ISI:000256242300017 |
|
no |
|
NU @ m-krug @ |
|
10392 |
| Permanent link to this record |
| |
|
| |
|
Lee, W.-S.; Chen, T.-H. |
|
Mechanical and microstructural response of aluminum-scandium (Al-Sc) alloy as a function of strain rate and temperature |
|
Journal Article |
|
2009 |
|
Materials Chemistry and Physics |
|
|
|
113 |
|
2-3 |
|
734-745 |
|
Al-Sc alloy; Strain rate sensitivity; Activation energy; Shearing; Dislocation; Precipitates |
|
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. |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
no |
|
NU @ karnesky @ |
|
10512 |
| Permanent link to this record |
| |
|
| |
|
Lee, W.S.; Chen, T.H. |
|
Effects of strain rate and temperature on dynamic mechanical behaviour and microstructural evolution in aluminium-scandium (Al-Sc) alloy |
|
Journal Article |
|
2008 |
|
Materials Science and Technology |
|
|
|
24 |
|
10 |
|
1271-1282 |
|
AL-SC ALLOY; STRAIN RATE SENSITIVITY; ACTIVATION ENERGY; ADIABATIC SHEARING; DISLOCATION; AL3SC PRECIPITATES |
|
The present study applies a compressive split Hopkinson bar to investigate the mechanical response, microstructural evolution and fracture characteristics of an aluminium-scandium (Al-Sc) alloy at temperatures ranging from − 100 to 300°C and strain rates of 1·2 × 103, 3·2×103 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 increasing 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. The Zerilli-Armstrong fcc constitutive model is used to describe the plastic deformation behaviour of the Al-Sc alloy, and the error between the predicted flow stress and the measured stress is found to be less than 5%. The fracture analysis results reveal that cracks initiate and propagate in the shear bands of the Al-Sc alloy specimens and are responsible for their ultimate failure. 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. Scanning electron microscopy observations show that the surfaces of the fractured specimens are characterised by transgranular dimpled features, which are indicative of ductile fracture. The depth and density of these dimples are significantly influenced by the strain rate and temperature. The transmission electron microscopy structural observations show the precipitation of Al3Sc particles in the matrix and at the grain boundaries. These particles suppress dislocation motion and result in a strengthening effect. The transmission electron microscopy analysis also reveals that the dislocation density increases, but the dislocation cell size decreases, with increasing strain rate for a constant level of strain. However, a higher temperature causes the dislocation density to decrease, thereby increasing the dislocation cell size. |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
no |
|
NU @ m-krug @ |
|
10531 |
| Permanent link to this record |
| |
|
| |
|
Lagow, B.W.; Robertson, I.M.; Jouiad, M.; Lassila, D.H.; Lee, T.C.; Birnbaum, H.K. |
|
Observation of dislocation dynamics in the electron microscope |
|
Journal Article |
|
2001 |
|
Materials Science And Engineering A |
|
Mater. Sci. Eng. A |
|
309-310 |
|
|
|
445-450 |
|
|
|
Deformation experiments performed in situ in the transmission electron microscope have led to an increased understanding of dislocation dynamics. To illustrate the capability of this technique two examples will be presented. In the first example, the processes of work hardening in Mo at room temperature will be presented. These studies have improved our understanding of dislocation mobility, dislocation generation, and dislocation-obstacle interactions. Zn the second example, the interaction of matrix dislocations with grain boundaries will be described. From such studies predictive criteria for slip transfer through grain boundaries have been developed. |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
0921-5093 |
|
|
|
|
|
|
|
|
|
|
|
WOS:000169044600089 |
|
no |
|
NU @ m-krug @ |
|
10533 |
| Permanent link to this record |
