“Asymmetrical superelastic behavior of thermomechanically processed semi-equiatomic NiTi alloy in tensile and compressive modes of deformation”. Safdel A, Zarei-Hanzaki A, Abedi HR, Pourbabak S, Schryvers D, Basu R, Journal Of Alloys And Compounds 878, 160443 (2021). http://doi.org/10.1016/J.JALLCOM.2021.160443
Abstract: In the present work two different cold working and annealing schemes were utilized, and the asymmetric superelastic response of thermomechanically processed materials were then assessed through cyclic tensile and compressive modes of deformation. The values of transformation stress, transformation strain, and pseudoelastic strain were measured for each treated and solutionized specimens and the asymmetric response was compared. In the solution annealed state, the difference of these parameters at different deformation modes was negligible due to the weak texture of the material, while for thermomechanically treated ones, development of specific deformation and recrystallization texture components was identified to be one of the underlying reasons of intensified asymmetry. The evolved substructure during the thermomechanical processing also played a substantial role in determining the asymmetric response. The presence of fine grains and dense dislocation substructure could hinder the movement of the transformation front, thus limiting the range of transformation. In tensile mode, the transformation stress was lower, but higher transformation strain was achieved, which was discussed relying on the slip activity in specified oriented grains. The lower transformation strain in compression mode led to lower pseudoelastic strain due to the narrow transformation range which finally degraded superelastic response of the material. (C) 2021 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 3.133
DOI: 10.1016/J.JALLCOM.2021.160443
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“Atomic-scale investigation of the heterogeneous precipitation in the E (Al₁₈Mg₃Cr₂) dispersoid of 7075 aluminum alloy”. Ding L, Zhao L, Weng Y, Schryvers D, Liu Q, Idrissi H, Journal Of Alloys And Compounds 851, 156890 (2021). http://doi.org/10.1016/J.JALLCOM.2020.156890
Abstract: The heterogeneous precipitation of the eta (MgZn2) phase on the E (Al18Mg3Cr2) dispersoids of the 7075 aluminum alloy was systematically investigated by atomic resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and energy dispersive X-ray spectrometry (EDX). It is found that coarse B particles are heterogeneously precipitated at the E particle interface after water quenching and isothermal aging at 120 degrees C. The incoherent E/Al interface is responsible for the high tendency of heterogeneous precipitation of the B phase. Two different orientation relationships (ORs) between the eta, E and Al matrix are identified: OR1 [2 (11) over bar0](eta)[011](E)//[(1) over bar 12](Al), (01 (1) over bar0)(eta)//(13 (3) over bar)(E)//(201)(Al), OR2 [(1) over bar 12](E)//[0001](eta)//[011](Al), (01 (1) over bar0 )(eta)//(220)(E)//(34 (4) over bar)(Al). The eta phase is preferential to nucleate along the {111}(E) or the {220}(E) planes, depending on its OR. The heterogeneous nucleation of B phase on the E particle could stabilize the E/Al interface by introducing a coherent E/eta interface, which increases the drive force of heterogeneous precipitation. The reorientation of eta phase and mutual diffusion of solute atoms could assist the coherency of the E/eta interface. The present results suggest that increasing the coherency of the E/Al interface is a promising method to suppress the heterogeneous precipitation of the eta phase. (C) 2020 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 3.133
DOI: 10.1016/J.JALLCOM.2020.156890
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“Quantified contribution of β&Prime, and β&prime, precipitates to the strengthening of an aged Al–Mg–Si alloy”. Yang M, Chen H, Orekhov A, Lu Q, Lan X, Li K, Zhang S, Song M, Kong Y, Schryvers D, Du Y, Materials Science And Engineering A-Structural Materials Properties Microstructure And Processing 774, 138776 (2020). http://doi.org/10.1016/j.msea.2019.138776
Abstract: It is generally believed that β00 precipitates, rather than β0 precipitates, are the major strengthening precipitates in
aged Al–Mg–Si alloys. The reason for this difference is not well understood. To clarify this, two samples of the
same Al–Mg–Si alloy but with different aging states were prepared. The under-aged sample only contains nanoprecipitates
of the β00 type, while the peak-aged one contains nearly equal volumes of β00 and β0 precipitates. We
have, for the first time, separated the strengthening effect of the contribution from βʺ and βʹ precipitates,
respectively, by an indirect approach based on high-precision measurements of volume fractions, number densities,
sizes, proportions of the precipitates, their lattice strains, the composition and grain size of the matrix. The
β0 precipitates, which take 45.6% of the total precipitate volume in the peak-aged sample, contribute to the entire
precipitation strengthening by only 31.6%. The main reason why they are less useful compared to β00 precipitates
has been found to be associated with their smaller lattice strains relative to the matrix, which is 0.99% versus
2.10% (for β00 ).
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 6.4
DOI: 10.1016/j.msea.2019.138776
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“Dislocation structures and the role of grain boundaries in cyclically deformed Ni micropillars”. Samaee V, Sandfeld S, Idrissi H, Groten J, Pardoen T, Schwaiger R, Schryvers D, Materials Science And Engineering A-Structural Materials Properties Microstructure And Processing 769, 138295 (2020). http://doi.org/10.1016/j.msea.2019.138295
Abstract: Transmission electron microscopy and finite element-based dislocation simulations were combined to study the development of dislocation microstructures after cyclic deformation of single crystal and bicrystal Ni micropillars oriented for multi-slip. A direct correlation between large accumulation of plastic strain and the presence of dislocation cell walls in the single crystal micropillars was observed, while the presence of the grain boundary hampered the formation of wall-like structures in agreement with a smaller accumulated plastic strain. Automated crystallographic orientation and nanostrain mapping using transmission electron microscopy revealed the presence of lattice heterogeneities associated to the cell walls including long range elastic strain fields. By combining the nanostrain mapping with an inverse modelling approach, information about dislocation density, line orientation and Burgers vector direction was derived, which is not accessible otherwise in such dense dislocation structures. Simulations showed that the image forces associated with the grain boundary in this specific bicrystal configuration have only a minor influence on dislocation behavior. Thus, the reduced occurrence of “mature” cell walls in the bicrystal can be attributed to the available volume, which is too small to accommodate cell structures.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 6.4
Times cited: 1
DOI: 10.1016/j.msea.2019.138295
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“Enhancement of toughness of Al-to-steel Friction Melt Bonded welds via metallic interlayers”. Jimenez-Mena N, Jacques PJ, Ding L, Gauquelin N, Schryvers D, Idrissi H, Delannay F, Simar A, Materials science and engineering: part A: structural materials: properties, microstructure and processing 740-741, 274 (2019). http://doi.org/10.1016/j.msea.2018.10.101
Abstract: The toughness of Al-to-steel welds decreases with increasing thickness of the intermetallic (IM) layer formed at the interface. Co plating has been added as interlayer in Al-to-steel Friction Melt Bonded (FMB) welds to control the nature and thickness of the IM layer. In comparison to a weld without interlayer, Co plating brings about a reduction of the thickness of the IM layer by 70%. The critical energy release rate of the crack propagating in the weld is used as an indicator of toughness. It is evaluated via an adapted crack propagation test using an energy conservation criterion. For a weld without interlayer, critical energy release rate is found to increase when the thickness of the intermetallic layer decreases. When the intermetallic layer is thick, the crack propagates in a brittle manner through the intermetallic whereas, at low layer thickness, the crack deviates and partially propagates through the Al plate, which causes an increase of toughness. The use of a Co interlayer brings about an increase of toughness by causing full deviation of the crack towards the Al plate.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 3.094
Times cited: 4
DOI: 10.1016/j.msea.2018.10.101
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“Effect of annealing on the transformation behavior and mechanical properties of two nanostructured Ti-50.8at.%Ni thin wires produced by different methods”. Wang X, Amin-Ahmadi B, Schryvers D, Verlinden B, Van Humbeeck J, Materials science forum 738/739, 306 (2013). http://doi.org/10.4028/www.scientific.net/MSF.738-739.306
Abstract: A Ti-50.8at.%Ni wire produced using a co-drawing method and a commercial Ti-50.8at.%Ni wire were annealed at different temperatures between 450°C and 700°C. Grains with diameter less than 100nm were revealed by transmission electron microscopy for both wires before annealing treatment. However, the microstructural heterogeneity of the co-drawn wire is more obvious than that of the commercial wire. Multi-stage martensitic transformation was observed in the co-drawn wire, compared with the one-stage A↔M transformation in the commercial wire after annealing at 600°C for 30min. The differences of total elongation, plateau strain and pseudoelastic recoverable strain between the commercial wire and the co-drawn wire were also observed. The differences of the transformation behavior and mechanical properties between the commercial wire and the co-drawn wire are attributed to the microstructural difference between these two wires.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Times cited: 5
DOI: 10.4028/www.scientific.net/MSF.738-739.306
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“EM characterization of precipitates in as-cast and annealed Ni45.5Ti45.5Nb9 shape memory alloys”. Shi H, Frenzel J, Schryvers D, Materials science forum 738/739, 113 (2013). http://doi.org/10.4028/www.scientific.net/MSF.738-739.113
Abstract: Nb-rich precipitates in the matrix of as-cast and annealed Ni45.5Ti45.5Nb9 alloys are investigated by scanning and scanning transmission electron microscopy, including slice-and-view and geometric phase analysis (GPA). The Nb-rich bcc nano-precipitates in the as-cast alloy have a 10% lattice parameter difference with the B2 matrix and reveal compensating interface dislocations. The 3D reconstruction of the configuration of small Nb-rich precipitates in the annealed alloy reveals a wall-like distribution of precipitates, which may increase the thermal hysteresis of the material.
Keywords: P1 Proceeding; Electron microscopy for materials research (EMAT)
Times cited: 1
DOI: 10.4028/www.scientific.net/MSF.738-739.113
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“Nano- and microcrystal investigations of precipitates, interfaces and strain fields in Ni-Ti-Nb by various TEM techniques”. Schryvers D, Shi H, Martinez GT, Van Aert S, Frenzel J, Van Humbeeck J, Materials science forum
T2 –, 9th European Symposium on Martensitic Transformations (ESOMAT 2012), SEP 09-16, 2012, St Petersburg, RUSSIA 738/739, 65 (2013). http://doi.org/10.4028/www.scientific.net/MSF.738-739.65
Abstract: In the present contribution several advanced electron microscopy techniques are employed in order to describe chemical and structural features of the nano- and microstructure of a Ni45.5Ti45.5Nb9 alloy. A line-up of Nb-rich nano-precipitates is found in the Ni-Ti-rich austenite of as-cast material. Concentration changes of the matrix after annealing are correlated with changes in the transformation temperatures. The formation of rows and plates of larger Nb-rich precipitates and particles is described. The interaction of a twinned martensite plate with a Nb-rich nano-precipitate is discussed and the substitution of Nb atoms on the Ti-sublattice in the matrix is confirmed.
Keywords: P1 Proceeding; Electron microscopy for materials research (EMAT)
Times cited: 2
DOI: 10.4028/www.scientific.net/MSF.738-739.65
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“Analysis of internal stress build-up during deposition of nanocrystalline Ni thin films using transmission electron microscopy”. Lumbeeck G, Delvaux A, Idrissi H, Proost J, Schryvers D, Thin solid films : an international journal on the science and technology of thin and thick films 707, 138076 (2020). http://doi.org/10.1016/j.tsf.2020.138076
Abstract: Ni thin films sputter-deposited at room temperature with varying Ar pressures were investigated with automated crystal orientation mapping in a transmission electron microscope to uncover the mechanisms controlling the internal stress build-up recorded in-situ during deposition. Large grains were found to induce behaviour similar to a stress-free nucleation layer. The measurements of grain size in most of the Ni thin films are in agreement with the island coalescence model. Low internal stress was observed at low Ar pressure and was explained by the presence of large grains. Relaxation of high internal stress was also noticed at the highest Ar pressure, which was attributed to a decrease of Σ3 twin boundary density due to a low deposition rate. The results provide insightful information to better understand the relationship between structural boundaries and the evolution of internal stress upon deposition of thin films.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
DOI: 10.1016/j.tsf.2020.138076
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“Determination of the atomic width of an APB in ordered CoPt using quantified HAADF-STEM”. Akamine H, Van den Bos KHW, Gauquelin N, Farjami S, Van Aert S, Schryvers D, Nishida M, Journal of alloys and compounds 644, 570 (2015). http://doi.org/10.1016/j.jallcom.2015.04.205
Abstract: Anti-phase boundaries (APBs) in an ordered CoPt alloy are planar defects which disturb the ordered structure in their vicinity and decrease the magnetic properties. However, it has not yet been clarified to what extend the APBs disturb the ordering. In this study, high-resolution HAADF-STEM images are statistically analysed based on the image intensities estimated by the statistical parameter estimation theory. In the procedure, averaging intensities, fitting the intensity profiles to specific functions, and assessment based on a statistical test are performed. As a result, the APBs in the stable CoPt are found to be characterised by two atomic planes, and a contrast transition range as well as the centre of an inclined APB is determined. These results show that the APBs are quite sharp and therefore may have no notable effect on the net magnetic properties due to their small volume fraction. (C) 2015 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 3.133
Times cited: 12
DOI: 10.1016/j.jallcom.2015.04.205
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“Stress-induced amorphization triggers deformation in the lithospheric mantle”. Samae V, Cordier P, Demouchy S, Bollinger C, Gasc J, Koizumi S, Mussi A, Schryvers D, Idrissi H, Nature 591, 82 (2021). http://doi.org/10.1038/S41586-021-03238-3
Abstract: The mechanical properties of olivine-rich rocks are key to determining the mechanical coupling between Earth's lithosphere and asthenosphere. In crystalline materials, the motion of crystal defects is fundamental to plastic flow(1-4.) However, because the main constituent of olivine-rich rocks does not have enough slip systems, additional deformation mechanisms are needed to satisfy strain conditions. Experimental studies have suggested a non-Newtonian, grain-size-sensitive mechanism in olivine involving grain-boundary sliding(5,6). However, very few microstructural investigations have been conducted on grain-boundary sliding, and there is no consensus on whether a single or multiple physical mechanisms are at play. Most importantly, there are no theoretical frameworks for incorporating the mechanics of grain boundaries in polycrystalline plasticity models. Here we identify a mechanism for deformation at grain boundaries in olivine-rich rocks. We show that, in forsterite, amorphization takes place at grain boundaries under stress and that the onset of ductility of olivine-rich rocks is due to the activation of grain-boundary mobility in these amorphous layers. This mechanism could trigger plastic processes in the deep Earth, where high-stress conditions are encountered (for example, at the brittle-plastic transition). Our proposed mechanism is especially relevant at the lithosphere-asthenosphere boundary, where olivine reaches the glass transition temperature, triggering a decrease in its viscosity and thus promoting grain-boundary sliding.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 40.137
DOI: 10.1038/S41586-021-03238-3
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“3D reconstruction of Ni4Ti3 precipitates in a Ni51Ti49 alloy in a FIB/SEM dual-beam system”. Cao S, Tirry W, van den Broek W, Schryvers D, Materials science forum 583, 277 (2008). http://doi.org/10.4028/www.scientific.net/MSF.583.277
Abstract: Ni4Ti3 precipitates play an important role in the shape memory and superelastic behaviour of thermo-mechanically treated Ni-Ti material. The 3D morphology and distribution of such precipitates with lenticular shape and rhombohedral atomic structure in the austenitic B2 matrix of a binary Ni-rich Ni-Ti alloy has been elucidated via a slice view procedure in a Dual-Beam FIB/SEM system. With the sequence of cross-section SE images obtained from the SEM, a 3D reconstruction has been achieved after proper alignment and image processing, from which both qualitative and quantitative analysis can be performed. Careful imaging is needed to ensure that all variants of the precipitates are observed with equal probability, regardless sample orientation. Moreover, due to the weak contrast of the precipitates, proper imaging conditions need to be selected to allow for semi-automated image treatment. Finally, a volume ratio of 10.2% for the Ni4Ti3 precipitates could be calculated, summed over all variants, which yields a net composition of Ni50.36Ti49.64 for the matrix, leading to an increase of 113 degrees for the martensitic start temperature Ms. Also, the expected relative orientation of the different variants of the precipitates could be confirmed. In the near future, other quantitative measures on the distribution of the precipitates can be expected.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
DOI: 10.4028/www.scientific.net/MSF.583.277
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“Microstructural dependence on middle eigenvalue in Ti-Ni-Au”. Shi H, Delville R, Srivastava V, James RD, Schryvers D, Journal of alloys and compounds 582, 703 (2013). http://doi.org/10.1016/j.jallcom.2013.08.132
Abstract: The microstructure of various compounds of the Ti-Ni-Au alloy system is investigated by transmission electron microscopy in relation with changing lattice parameters improving the compatibility conditions between austenite and martensite expressed by the lambda(2) = 1 equation based on the Geometrically NonLinear Theory of Martensite (GNLTM). Although local differences in microstructure are observed, when increasing the gold content compound twins are replaced by Type I twins, while twinned lamellar structures are replaced by untwinned plates and self-accommodating structures when lambda(2) = 1 is approached, all confirming the predictions of the GNLTM. (c) 2013 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 3.133
Times cited: 8
DOI: 10.1016/j.jallcom.2013.08.132
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“Atomic structure of alloys close to phase transitions”. Van Tendeloo G, Schryvers D, Nucleation and growth processes in materials 580, 283 (2000)
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
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“Morphological characterization and distribution of autocatalytic-grown Ni4Ti3 precipitates in a Ni-Ti single crystal”. Cao S, Ke CB, Zhang XP, Schryvers D, Journal of alloys and compounds 577, 215 (2013). http://doi.org/10.1016/j.jallcom.2012.02.013
Abstract: The 3D size, morphology and distribution of autocatalytic-grown Ni4Ti3 precipitates in a Ni51Ti49 single crystal were characterized via a FIB/SEM Slice-and-View procedure and phase-field simulation. Important parameters on size and shape of the precipitates were measured. The pair distribution function and the minimum distance between two precipitates from different variants were calculated to describe the 3D distribution of the autocatalytic-grown Ni4Ti3 precipitates in single crystal Ni-Ti, with a comparison to the polycrystalline Ni50.8Ti49.2 alloy. Phase-field simulation was conducted to study the nucleation behavior of precipitates in the single crystal Ni-Ti. (C) 2012 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 3.133
Times cited: 5
DOI: 10.1016/j.jallcom.2012.02.013
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“Recent EM investigations on nano-and micro-defect structures in SMAs”. Schryvers D, Cao S, Pourbabak, Shi H, Lu, Journal of alloys and compounds 577, S705 (2013). http://doi.org/10.1016/j.jallcom.2011.10.112
Abstract: The present contribution reviews some recent electron microscopy investigations on different shape memory systems in which a variety of nano- and micro-defect structures play an essential role in the functional behaviour of the material. (NiTi3)-Ti-4 precipitates in Ni-Ti are a well-known example for which the focus is now on the 3D configurations, in Ni-Ti-Nb Nb-rich nanoprecipitates are thought to have a large impact on the hysteresis, in Co-Ni-Al an Al-enriched zone nearby the y'-precipitates yields a small sandwiched austenite while some first signs of quasidynamical lattice deformation in non-frozen Ni-Ti strain glass are measured by Cs-aberration-corrected transmission electron microscopy. (C) 2011 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 3.133
Times cited: 7
DOI: 10.1016/j.jallcom.2011.10.112
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“Microstructure and precipitates in annealed Co38Ni33Al29 ferromagnetic shape memory alloy”. Lu JB, Shi H, Sedlakova-Ignacova S, Espinoza R, Kopeček J, Sittner P, Bártová, B, Schryvers D, Journal of alloys and compounds 572, 5 (2013). http://doi.org/10.1016/j.jallcom.2013.03.228
Abstract: Transmission electron microscopy was performed to investigate the microstructure and precipitates in the annealed Co38Ni33Al29 ferromagnetic shape memory alloy. Apart from the dendritic secondary phase in the austenite matrix, micron-sized (up to 100 μm) fcc-based precipitates with partial γ′ L12 ordering and containing none, one or three {1 1 1}p parallel twin planes were found. The orientation relationship between the precipitates and matrix was found to be KurdjumovSachs. STEMEDX analysis indicates that twinned and non-twinned precipitates are Co-rich and Al- and Ni-deficient with respect to the matrix and with a lower Co/Al ratio for the latter. The 3D morphologies of precipitates were reconstructed with focused ion beam/scanning electron microscope dual-beam slice-and-view imaging, showing that the single {1 1 1}p plane twinned precipitates have a plate-like shape while the non-twinned precipitates are lath-like and often bent.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 3.133
Times cited: 10
DOI: 10.1016/j.jallcom.2013.03.228
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“Characterization of IASCC crack tips extracted from neutron-irradiated flux thimble tube specimens in view of a probabilistic fracture model”. Penders AG, Konstantinović, MJ, Van Renterghem W, Bosch R-W, Schryvers D, Somville F, Journal of nuclear materials 571, 154015 (2022). http://doi.org/10.1016/J.JNUCMAT.2022.154015
Abstract: This study reports the properties of irradiation assisted stress corrosion crack tips extracted by means of focused-ion beam from 60 to 80 dpa neutron-irradiated O-ring specimens tested under straining conditions under a pressurized-water reactor environment. Various crack tip morphologies and surrounding deformation features were analyzed as a function of applied stress, surface oxidation state and loading form – constant versus cyclic. All investigated cracks exhibit grain boundary oxidation in front of the crack tip, with the extent of oxidation being proportional to applied stress. These findings clearly demonstrate that, under the subcritical crack propagation regime, the grain boundary oxide grows faster than the crack. On the other hand, crack tips appertaining to specimens with removed oxide layer at the outer surface show comparatively less oxidation at the crack tip, which could indicate towards crack initiation from regions that exemplify lower stress, such as the O-ring inner surface. Cyclic loading is found to have a more pronounced effect on the crack tip microstructure, demonstrating increased deformation twinning and -martensitic transformation, which signifies towards an increased susceptibility to intergranular failure. Still, the extent of crack tip grain boundary oxidation in this case agrees well with expected values for maximum stress applied during cyclic loading. All results are interpreted based on the probabilistic subcritical crack propagation mechanism and provide strong support to a stress-driven internal oxidation model.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 3.1
DOI: 10.1016/J.JNUCMAT.2022.154015
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“Microstructural investigation of IASCC crack tips extracted from thimble tube O-ring specimens”. Penders AG, Konstantinovic MJ, Yang T, Bosch R-w, Schryvers D, Somville F, Journal of nuclear materials 565, 153727 (2022). http://doi.org/10.1016/J.JNUCMAT.2022.153727
Abstract: The microstructural features of intergranular irradiation-assisted stress corrosion crack tips from a redeemed neutron-irradiated flux thimble tube (60 dpa) have been investigated using focused-ion beam analysis and (scanning) transmission electron microscopy. The current work presents a close examination of the deformation field and oxide assembly associated with intergranular cracking, in addition to the analysis of radiation-induced segregation at leading grain boundaries. Evidence of stress induced martensitic transformation extending from the crack tips is presented. Intergranular crack arrest is demonstrated on the account of the external tensile stress orientation, and as a consequence of MnS inclusion particles segregating close to the fractured grain boundary. Exclusive observations of grain boundary oxidation prior to the cracking are presented, which is in full-agreement with the internal oxidation model.(c) 2022 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 3.1
DOI: 10.1016/J.JNUCMAT.2022.153727
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“Effect of deposition rate on the microstructure of electron beam evaporated nanocrystalline palladium thin films”. Amin-Ahmadi B, Idrissi H, Galceran M, Colla MS, Raskin JP, Pardoen T, Godet S, Schryvers D, Thin solid films : an international journal on the science and technology of thin and thick films 539, 145 (2013). http://doi.org/10.1016/j.tsf.2013.05.083
Abstract: The influence of the deposition rate on the formation of growth twins in nanocrystalline Pd films deposited by electron beam evaporation is investigated using transmission electron microscopy. Statistical measurements prove that twin boundary (TB) density and volume fraction of grains containing twins increase with increasing deposition rate. A clear increase of the dislocation density was observed for the highest deposition rate of 5 Å/s, caused by the increase of the internal stress building up during deposition. Based on crystallographic orientation indexation using transmission electron microscopy, it can be concluded that a {111} crystallographic texture increases with increasing deposition rate even though the {101} crystallographic texture remains dominant. Most of the TBs are fully coherent without any residual dislocations. However, for the highest deposition rate (5 Å/s), the coherency of the TBs decreases significantly as a result of the interaction of lattice dislocations emitted during deposition with the growth TBs. The analysis of the grain boundary character of different Pd films shows that an increasing fraction of high angle grain boundaries with misorientation angles around 5565° leads to a higher potential for twin formation.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.879
Times cited: 13
DOI: 10.1016/j.tsf.2013.05.083
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“Importance of twinning in static and dynamic compression of a Ti-6Al-4V titanium alloy with an equiaxed microstructure”. Coghe F, Tirry W, Rabet L, Schryvers D, Van Houtte P, Materials science and engineering: part A: structural materials: properties, microstructure and processing 537, 1 (2012). http://doi.org/10.1016/j.msea.2011.12.047
Abstract: Whereas deformation twinning is known to be an important deformation mechanism for hexagonal materials like magnesium and pure titanium, so far almost no literature exists on the twinning behaviour of the Ti-6Al-4V alloy. In this work it was shown that the activation of twinning as a deformation mechanism could have a pronounced effect on the mechanical behaviour of the Ti-6Al-4V alloy. This effect is even more pronounced under dynamic loading conditions. Transmission electron microscopy showed that only the {1 0 1 2}{1 0 1 1} tensile twin system was activated under certain loading conditions. Light-optical microscopy and electron backscatter diffraction data were afterwards used to experimentally determine the twin fractions. The importance of twinning for the texture evolution was also studied. It was shown that even small twin fractions can lead to distinct texture features, especially due to the discrete reorientation of the c-axes. The experimental results were compared to simulated results that were obtained with a viscoplastic self-consistent crystal plasticity code, after experimental validation that twinning can be reliably modelled as a unidirectional slip system. Although good agreement was obtained for the experimental and simulated stress-strain curves, the simulated results concerning twinning correlated well only on a qualitative basis as the simulated twin fractions were systematically higher than the experimental fractions. This seems to strengthen the hypothesis made by other research groups that complete grains might reorient by twinning. (C) 2011 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 3.094
Times cited: 35
DOI: 10.1016/j.msea.2011.12.047
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“A multi-scale characterization of deformation twins in Ti6Al4V sheet material deformed by simple shear”. Tirry W, Coghe F, Bouvier S, Gasperini M, Rabet L, Schryvers D, Materials science and engineering: part A: structural materials: properties, microstructure and processing 527, 4136 (2010). http://doi.org/10.1016/j.msea.2010.03.039
Abstract: Ti6Al4V sheet material is subjected to simple shear deformation with strain ratio's of 10%, 30% and 50%. Optical microscopy, transmission electron microscopy and electron backscatter diffraction techniques are applied to study the presence and morphology of deformation twins. Only the View the MathML source type of twins seems to be present with a volume fraction below 1%. These View the MathML source twins show a high density of basal stacking faults of the ABABACAC type identified using atomic resolution transmission electron microscopy. A resolved shear stress analysis shows that twins most often occur on those planes with the highest resolved shear stresses, but that the starting texture is not beneficial for the occurrence of twins. It is further suggested that a transitory strain hardening regime observed around 530 MPa might be related with the onset of twinning.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.094
Times cited: 20
DOI: 10.1016/j.msea.2010.03.039
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“Tailoring the Ti-C nanoprecipitate population and microstructure of titanium stabilized austenitic steels”. Cautaerts N, Delville R, Stergar E, Schryvers D, Verwerft M, Journal of nuclear materials 507, 177 (2018). http://doi.org/10.1016/J.JNUCMAT.2018.04.041
Abstract: The present work reports on the microstructural evolution of a new heat of 24% cold worked austenitic DIN 1.4970 (15-15Ti) nuclear cladding steel subjected to ageing heat treatments of varying duration between 500 and 800 degrees C (by steps of 100 degrees C). The primary aim was studying the finely dispersed Ti-C nanoprecipitate population, which are thought to be beneficial for creep and swelling resistance during service. Their size distribution and number density were estimated through dark field imaging and bright field Moire imaging techniques in the transmission electron microscope. Nanoprecipitates formed at and above 600 degrees C, which is a lower temperature than previously reported. The observed nucleation, growth and coarsening behavior of the nanoprecipitates were consistent with simple diffusion arguments. The formation of nanoprecipitates coincided with significant dissociation of dislocations as evidenced by weak beam dark field imaging. Possible mechanisms, including Silcock's stacking fault growth model and Suzuki segregation, are discussed. Recrystallization observed after extended ageing at 800 degrees C caused the redissolution of nanoprecipitates. Large primary Ti(C,N) and (Ti,Mo)C precipitates that occur in the as-received material, and M23C6 precipitates that nucleate on grain boundaries at low temperatures were also characterized by a selective dissolution procedure involving filtration, X-ray diffraction and quantitative Rietveld refinement. The partitioning of key elements between the different phases was derived by combining these findings and was consistent with thermodynamic considerations and the processing history of the steel. (C) 2018 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 2.048
Times cited: 1
DOI: 10.1016/J.JNUCMAT.2018.04.041
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“Dissolution corrosion of 316L austenitic stainless steels in contact with static liquid lead-bismuth eutectic (LBE) at 500 °C”. Lambrinou K, Charalampopoulou E, Van der Donck T, Delville R, Schryvers D, Journal of nuclear materials 490, 9 (2017). http://doi.org/10.1016/j.jnucmat.2017.04.004
Abstract: This work addresses the dissolution corrosion behaviour of 316L austenitic stainless steels. For this purpose, solution-annealed and cold-deformed 316L steels were simultaneously exposed to oxygen-poor (<10-8 mass%) static liquid lead-bismuth eutectic (LBE) for 253e3282 h at 500 °C. Corrosion was consistently more severe for the cold-drawn steels than the solution-annealed steel, indicating the importance of the steel thermomechanical state. The thickness of the dissolution-affected zone was nonuniform, and sites of locally-enhanced dissolution were occasionally observed. The progress of LBE dissolution attack was promoted by the interplay of certain steel microstructural features (grain boundaries, deformation twin laths, precipitates) with the dissolution corrosion process. The identified dissolution mechanisms were selective leaching leading to steel ferritization, and non-selective leaching; the latter was mainly observed in the solution-annealed steel. The maximum corrosion rate decreased with exposure time and was found to be inversely proportional to the depth of dissolution attack.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 2.048
Times cited: 24
DOI: 10.1016/j.jnucmat.2017.04.004
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“Effect of annealing on cold-rolled Ni-Ti alloys”. Srivastava AK, Yang Z, Schryvers D, van Hurnbeeck J, Materials science and engineering: part A: structural materials: properties, microstructure and processing 481, 594 (2008). http://doi.org/10.1016/j.msea.2006.12.216
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.094
Times cited: 8
DOI: 10.1016/j.msea.2006.12.216
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“Electron energy-loss spectroscopy study of NiTi shape memory alloys”. Yang ZQ, Schryvers D, Materials science and engineering: part A: structural materials: properties, microstructure and processing 481, 214 (2008). http://doi.org/10.1016/j.msea.2006.12.227
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.094
Times cited: 7
DOI: 10.1016/j.msea.2006.12.227
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“In situ transmission electron microscopy of stress-induced martensite with focus on martensite twinning”. Tirry W, Schryvers D, Materials science and engineering: part A: structural materials: properties, microstructure and processing 481, 420 (2008). http://doi.org/10.1016/j.msea.2006.12.214
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.094
Times cited: 22
DOI: 10.1016/j.msea.2006.12.214
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“New (3(3)under-bar) long-period microtwin variant in the martensitic phase of the PtTi alloy”. Rotaru G-M, Schryvers D, Materials science and engineering: part A: structural materials: properties, microstructure and processing 481, 437 (2008). http://doi.org/10.1016/j.msea.2006.12.201
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.094
Times cited: 3
DOI: 10.1016/j.msea.2006.12.201
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“Measuring strain fields and concentration gradients around Ni4Ti3 precipitates”. Schryvers D, Tirry W, Yang ZQ;, Materials science and engineering A: structural materials properties microstructure and processing 438, 485 (2006). http://doi.org/10.1016/j.msea.2006.02.166
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.094
Times cited: 35
DOI: 10.1016/j.msea.2006.02.166
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“Quantitative determination of the crystal structure of Ni4Ti3 precipitates”. Tirry W, Schryvers D, Jorissen K, Lamoen D, Materials science and engineering: part A: structural materials: properties, microstructure and processing 438, 517 (2006). http://doi.org/10.1016/j.msea.2006.02.063
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.094
Times cited: 7
DOI: 10.1016/j.msea.2006.02.063
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