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Type Cerezo, A.; Godfrey, T. J.; Sijbrandij, S. J.; Smith, G. D. W.; Warren, P. J.
  Publication Performance of an energy-compensated three-dimensional atom probe Volume Journal Article
Pages 1998
  Abstract Review of Scientific Instruments  
  Corporate Author Rev. Sci. Instrum.  
Publisher 69  
Editor 1
  Summary Language 49-58 Series Editor atom probe field ion microscopy  
Abbreviated Series Title A wide acceptance angle first-order reflectron lens has been incorporated into a three-dimensional atom probe (3DAP) to provide improved mass resolution. This new 3DAP instrument is capable of resolving isotopes in the mass spectrum, with resolutions better than m/Delta m = 500 full width at half maximum and 250 full width at 10% maximum. However, use of a reflectron for energy compensation within an imaging system means that improvements in mass resolution result in degradation of the spatial resolution. This article addresses the detailed design of the energy compensated 3DAP, and the minimization and compensation of chromatic aberrations in the imaging performance of the instrument. Some applications of the new instrument are included to illustrate its capabilities in the atomic-scale analysis of engineering alloys.
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no NU @ karnesky @ 459
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Furuno, Kazuko; Akamatsu, Hiroki; Oh-ishi, Keiichiro; Furukawa, Minoru; Horita, Zenji; Langdon, Terence G. Microstructural development in equal-channel angular pressing using a 60° die Journal Article 2004 Acta Materialia Acta Mater. 52 9 2497-2507 Aluminum; Equal-channel angular pressing; Grain boundary misorientations; Texture; Ultrafine-grained microstructures Billets of pure aluminum and an Al1%Mg0.2%Sc alloy were successfully processed using equal-channel angular pressing (ECAP) with a die having an internal channel angle of 60°. Careful inspection of the microstructures after ECAP revealed excellent agreement, at both the macroscopic and the microscopic levels, with the theoretical predictions for shearing using a 60° die. The grain sizes introduced with the 60° die were slightly smaller than with a conventional 90° die; thus, the values with these two dies were ~1.1 and ~1.2 small mu, Greekm in pure Al and ~0.30 and ~0.36 small mu, Greekm in the AlMgSc alloy, respectively. Tensile testing of the pure aluminum at room temperature revealed similar strengthening after processing using either a 60° or a 90° die. In tests conducted at 673 K, the AlMgSc alloy processed with the 60° die exhibited significantly higher elongations to failure due primarily to the larger strain imposed with this die. It is shown using orientation imaging microscopy that superplastic flow in the AlMgSc alloy produces an essentially random texture and a distribution of boundary misorientations that approximates to the theoretical distribution for an array of randomly oriented grains. no NU @ karnesky @ 530
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Gómez de Salazar, J. M. ; Barrena, M. I. Role of Al2O3 particulate reinforcements on precipitation in 7005 Al-matrix composites Journal Article 2001 Scripta Materialia Scripta Mater. 44 10 2489-2495 Aluminum; Composites; Microstructure; Intermetallics phases; TEM no NU @ karnesky @ 533
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Han, Bing Q.; Langdon, Terence G. Factors contributing to creep strengthening in discontinuously-reinforced materials Journal Article 2002 Materials Science and Engineering A Mater. Sci. Eng. A 322 1-2 73-78 Composites; Creep; Load transfer; Substructure strengthening; Threshold stress There have been several experimental investigations of the creep behavior of materials with discontinuous reinforcement. For these materials, logarithmic plots of the steady-state or minimum strain rate against the applied stress usually reveal significant curvature such that the stress exponent, determined from the slope of the line, increases with decreasing stress. Plots of this nature are usually interpreted by invoking a threshold stress, o and replacing the applied stress, , with an effective stress, defined as (−o). This paper examines the implications of this approach using published creep data for several aluminum-based materials. It is shown that the introduction of an effective stress leads to a stress exponent that is similar to that observed in the unreinforced matrix material but, nevertheless, the creep rates in the reinforced materials are often significantly slower than in the matrix. This difference is examined with reference to the occurrence of load transfer and substructure strengthening. no NU @ karnesky @ 541
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Hunt, Warren H. Jr.; Maruyama, Benji The World Still Wont Beat a Path to Your Door: Transitioning DRA to the Marketplace Journal Article 1999 JOM 51 11 62-64 no NU @ karnesky @ 549
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Li, Yong; Langdon, Terence G. Creep behavior of an Al-6061 metal matrix composite reinforced with alumina particulates Journal Article 1997 Acta Materialia Acta Mater. 45 11 4797-4806 Creep tests were conducted on an Al-6061 matrix alloy reinforced with 20 vol.% of irregularly shaped Al2O3 particulates. The composite was fabricated using an ingot metallurgy technique and the creep properties were determined at temperatures from 623 to 773 K. The results show high values for both the apparent stress exponent (up to > 10) and the apparent activation energy for creep (~ 200–275 kJ/mol) but it is demonstrated, by incorporating a threshold stress into the analysis, that the true stress exponent is close to 3 and the true activation energy is close to the value for diffusion of Mg in the Al matrix. The results suggest that creep is controlled by the viscous glide of dislocations in the Al-6061 matrix alloy. Very fast creep rates are observed at the highest stress levels owing to the breakaway of dislocations from their solute atom atmospheres. Direct comparison shows that the creep resistance of this composite is less than in an Al-6061 alloy reinforced with 20 vol.% of Al2O3 microspheres. This difference is attributed to the creation of additional precipitates in the microsphere-reinforced composite because of an interfacial reaction between the matrix alloy and the reinforcement. no NU @ karnesky @ 562
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Li, Yong; Langdon, Terrence G. A simple procedure for estimating threshold stresses in the creep of metal matrix composites Journal Article 1997 Scripta Materialia Scripta Mater. 36 12 1457-1460 no NU @ karnesky @ 563
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My, Yan; Langdon, Terence G. Creep behavior of an Al-6061 metal matrix composite produced by liquid metallurgy processing Journal Article 1997 Materials Science and Engineering A Mater. Sci. Eng. A 230 1-2 183-187 Activation energy; Alumina microspheres; Aluminum composite; Creep; Stress exponent; Threshold stress Constant stress creep tests were conducted on an Al-6061 metal matrix composite reinforced with alumina microspheres and produced using liquid metallurgy processing. By introducing a threshold stress into the creep analysis, it is concluded that creep occurs by viscous glide in the matrix with a stress exponent of ≈ 3 and an activation energy of ≈125 kJ mol−1. The threshold stress is probably associated with the presence of fine spinel crystals which have been identified in the matrix of the composite. no NU @ karnesky @ 715
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Deconihout, B.; Vurpillot, F.; Bouet, M.; Renaud, L. Improved ion detection efficiency of microchannel plate detectors Journal Article 2002 Review of Scientific Instruments Rev. Sci. Instrum. 73 4 1734-1740 The knowledge of the detection efficiency of the microchannel plate is of upmost importance in many applications using this type of particle detector. However, few attempts have been made to measure the absolute value of the detection efficiency of microchannel plates. In this article, a new way of accurately measuring the absolute value of the detection efficiency is described. When particles hit the detector in the interchannel web of the microchannel plate, secondary electrons are generated. These secondary electrons can be returned to neighboring channels by means of an electric field applied at the front face of the detector. The resulting increase in the detection efficiency has been quantified using the absolute measurement of the detection efficiency. It is found that the value of the returning field has to be carefully set in order to prevent detection artifacts that may lead to a wrong estimation of the detection efficiency. In the best conditions, the detection efficiency increase reaches 40%. no NU @ karnesky @ 806
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Zhang, Y.; Blazquez, J.S.; Conde, A.; Warren, P.J.; Cerezo, A. Partitioning of Co during crystallisation of FeCoNbB(Cu) amorphous alloys Journal Article 2003 Materials Science and Engineering A Mater. Sci. Eng. A 353 1-2 158-163 Amorphous; Soft magnetic; Atom probe; Nanocrystallisation; Microstructure Partitioning behaviour of alloying elements during the primary crystallisation of both Fe18Co60Nb6B16 and Fe39Co39Nb6B15Cu1 alloys has been studied using three-dimensional atom probe (3DAP). Cu rich clusters were found in the Cu-containing alloy, and they provided nucleation sites for the primary α-Fe(Co) particles. In the Cu clusters, concentration of both Fe and Co was greatly decreased. In both Cu-containing and Cu-free alloys Nb and B were depleted in the α-Fe(Co) particles and enriched in the remaining amorphous phase. However, Co concentration in the α-Fe(Co) was the same as the remaining amorphous phase. Based on the 3DAP analysis, the phase volume fraction has been estimated. no NU @ karnesky @ 818
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