“On the mechanism of twin formation in FeMnC TWIP steels”. Idrissi H, Renard K, Ryelandt L, Schryvers D, Jacques PJ, Acta materialia 58, 2464 (2010). http://doi.org/10.1016/j.actamat.2009.12.032
Abstract: Although it is well known that FeMnC TWIP steels exhibit high work-hardening rates, the elementary twinning mechanisms controlling the plastic deformation of these steels have still not been characterized. The aim of the present study is to analyse the extended defects related to the twinning occurrence using transmission electron microscopy. Based on these observations, the very early stage of twin nucleation can be attributed to the pole mechanism with deviation proposed by Cohen and Weertman or to the model of Miura, Takamura and Narita, while the twin growth is controlled by the pole mechanism proposed by Venables. High densities of sessile Frank dislocations are observed within the twins at the early stage of deformation, which can affect the growth and the stability of the twins, but also the strength of these twins and their interactions with the gliding dislocations present in the matrix. This experimental evidence is discussed and compared to recent results in order to relate the defects analysis to the macroscopic behaviour of this category of material.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 5.301
Times cited: 244
DOI: 10.1016/j.actamat.2009.12.032
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“Oxidation processes at the metal/oxide interface in CoFe2/CoFe2O4 bilayers deposited by pulsed laser deposition”. Viart N, Sayed Hassan R, Ulhaq-Bouillet C, Meny C, Panissod P, Loison JL, Versini G, Huber F, Pourroy G, Verbeeck J, Van Tendeloo G, Acta materialia 54, 191 (2006). http://doi.org/10.1016/j.actamat.2005.08.041
Abstract: CoFe2/CoFe2O4 bilayers were made by pulsed laser ablation of a CoFe2 target on Si(I 0 0) substrates. The metallic layer was deposited first, in vacuum. The oxide was then deposited in an oxidizing O-2:N-2 (20:80) atmosphere. Two different procedures were used for the introduction of the oxidizing atmosphere in the deposition chamber: the laser ablation of the target was either stopped (discontinuous deposition process) or maintained (continuous deposition process) during the 20 min necessary for the establishment of the desired O-2:N-2 pressure. In both cases, the different electronegativities of Fe and Co cause an important modification of the Fe/Co ratio at the metal/oxide interface, with a depletion of Fe in the metal region and of Co in the oxide region. In the continuous procedure, the combination of the kinetic energy given by the ablation process to the Fe and Co adatoms with the one they get from their different affinity towards oxidation allows the formation of a low roughness metal/oxide interface with a high (111) preferred orientation of the CoFe2O4 layer, an induced re-crystallisation of the metal layer underneath and an unusual antiferromagnetic metal/oxide magnetic coupling. (c) 2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 5.301
Times cited: 5
DOI: 10.1016/j.actamat.2005.08.041
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“Quantitative determination of strain fields around Ni4Ti3 precipitates in NiTi”. Tirry W, Schryvers D, Acta materialia 53, 1041 (2005). http://doi.org/10.1016/j.actamat.2004.10.049
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 5.301
Times cited: 97
DOI: 10.1016/j.actamat.2004.10.049
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“Quantitative three-dimensional analysis of Ni4Ti3 precipitate morphology and distribution in polycrystalline Ni-Ti”. Cao S, Nishida M, Schryvers D, Acta materialia 59, 1780 (2011). http://doi.org/10.1016/j.actamat.2010.11.044
Abstract: The three-dimensional size, morphology and distribution of Ni4Ti3 precipitates in a Ni50.8Ti49.2 polycrystalline shape memory alloy with a heterogeneous microstructure have been investigated using a focused ion beam/scanning electron microscopy slice-and-view procedure. The mean volume, central plane diameter, thickness, aspect ratio and sphericity of the precipitates in the grain interior as well as near to the grain boundary were measured and/or calculated. The morphology of the precipitates was quantified by determining the equivalent ellipsoids with the same moments of inertia and classified according to the Zingg scheme. Also, the pair distribution functions describing the three-dimensional distributions were obtained from the coordinates of the precipitate mass centres. Based on this new data it is suggested that the existence of the heterogeneous microstructure could be due to a very small concentration gradient in the grains of the homogenized material and that the resulting multistage martensitic transformation originates in strain effects related to the size of the precipitates and scale differences of the available B2 matrix in between the precipitates.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 5.301
Times cited: 34
DOI: 10.1016/j.actamat.2010.11.044
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“Site occupation of Nb atoms in ternary Ni-Ti-Nb shape memory alloys”. Shi H, Frenzel J, Martinez GT, Van Rompaey S, Bakulin A, Kulkova A, Van Aert S, Schryvers D, Acta materialia 74, 85 (2014). http://doi.org/10.1016/j.actamat.2014.03.062
Abstract: Nb occupancy in the austenite B2-NiTi matrix and Ti2Ni phase in NiTiNb shape memory alloys was investigated by aberration-corrected scanning transmission electron microscopy and precession electron diffraction. In both cases, Nb atoms were found to prefer to occupy the Ti rather than Ni sites. A projector augmented wave method within density functional theory was used to calculate the atomic and electronic structures of the austenitic B2-NiTi matrix phase and the Ti2Ni precipitates both with and without addition of Nb. The obtained formation energies and analysis of structural and electronic characteristics explain the preference for Ti sites for Nb over Ni sites.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 5.301
Times cited: 21
DOI: 10.1016/j.actamat.2014.03.062
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“Chemical stability of YBiO3 buffer layers for implementation in YBa2Cu3O7-&delta, coated conductors”. Pollefeyt G, Meledin A, Pop C, Ricart S, Hühne R, Van Tendeloo G, Van Driessche I, Acta materialia 100, 224 (2015). http://doi.org/10.1016/j.actamat.2015.08.023
Abstract: In this work, the chemical and microstructural stability of YBiO3 buffer layers during the growth of YBa2Cu3O7-δ (YBCO) was studied. The superconducting YBCO films were deposited via both Pulsed Laser Deposition as well as Chemical Solution Deposition. Although excellent superconducting properties are obtained in both cases, self-field critical current densities of 3.6 and 1.2 MA/cm2 respectively, chemical instability of the YBiO3 buffer layer is observed. An elaborate transmission electron microscopy study showed that in the case of vacuum deposited YBCO, the YBiO3 becomes unstable and Bi2O3 sublimates out of the architecture. Due to this structural instability, an intermediate Y2O3 layer is obtained which maintains it microstructural orientation relation with the substrate and acts as growth template for YBCO. For chemical solution deposited YBCO, reaction of YBCO with the YBiO3 buffer layer is observed, leading to large grains of YBa2BiO6 which are pushed towards the surface of the films and strongly reduce the superconducting properties. Upon using high growth temperatures for the superconducting layer, these secondary phases decompose, which subsequently leads to Bi2O3 sublimation and a textured YBCO film which directly nucleated onto the LaAlO3 single crystal substrate. Hence, this electron microscopy study indicates that bismuth-based buffer layers systems are not suitable for implementation in coated conductors.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 5.301
DOI: 10.1016/j.actamat.2015.08.023
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“TEM investigation of the microstructure and defects of CuZr martensite: 1: morphology and twin systems”. Seo JW, Schryvers D, Acta materialia 46, 1165 (1998). http://doi.org/10.1016/S1359-6454(97)00333-9
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 5.301
Times cited: 46
DOI: 10.1016/S1359-6454(97)00333-9
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“TEM investigation of the microstructure and defects of CuZr martensite: 2: planar defects”. Seo JW, Schryvers D, Acta materialia 46, 1177 (1998). http://doi.org/10.1016/S1359-6454(97)00334-0
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 5.301
Times cited: 21
DOI: 10.1016/S1359-6454(97)00334-0
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“A weak compatibility condition for precipitation with application to the microstructure of PbTe-Sb2Te3 thermoelectrics”. Chen X, Cao S, Ikeda T, Srivastava V, Snyder GJ, Schryvers D, James RD, Acta materialia 59, 6124 (2011). http://doi.org/10.1016/j.actamat.2011.06.025
Abstract: We propose a weak condition of compatibility between phases applicable to cases exhibiting full or partial coherence and Widmanstätten microstructure. The condition is applied to the study of Sb2Te3 precipitates in a PbTe matrix in a thermoelectric alloy. The weak condition of compatibility predicts elongated precipitates lying on a cone determined by a transformation stretch tensor. Comparison of this cone with the long directions of precipitates determined by a slice-and-view method of scanning electron microscopy combined with focused ion beam sectioning shows good agreement between theory and experiment. A further study of the morphology of precipitates by the Eshelby method suggests that interfacial energy also plays a role and gives an approximate value of interfacial energy per unit area of 250 dyn cm−1.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 5.301
Times cited: 8
DOI: 10.1016/j.actamat.2011.06.025
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