“Interfacial characteristics and cohesion mechanisms of linear friction welded dissimilar titanium alloys: Ti–5Al–2Sn–2Zr–4Mo–4Cr (Ti17) and Ti–6Al–2Sn–4Zr–2Mo (Ti6242)”. Boyat X, Ballat-Durand D, Marteau J, Bouvier S, Favergeon J, Orekhov A, Schryvers D, Materials characterization 158, 109942 (2019). http://doi.org/10.1016/j.matchar.2019.109942
Abstract: A detailed microstructural examination endeavoring to understand the interfacial phenomena yielding to cohesion
in solid-state assembling processes was performed. This study focuses on the transition zone of a dissimilar
titanium alloy joint obtained by Linear Friction Welding (LFW) the β-metastable Ti17 to the near-α
Ti6242. The transition zone delimitating both alloys is characterized by a sharp microstructure change from
acicular HCP (Hexagonal Close-Packed) α′ martensitic laths in the Ti6242 to equiaxed BCC β (Body-Centered
Cubic) subgrains in the Ti17; these α′ plates were shown to precipitate within prior-β subgrains remarkably more
rotated than the ones formed in the Ti17. Both α′ and β microstructures were found to be intermingled within
transitional subgrains demarcating a limited gradient from one chemical composition to the other. These peculiar
interfacial grains revealed that the cohesive mechanisms between the rubbing surfaces occurred in the
single-phase β domain under severe strain and high-temperature conditions. During the hot deformation process,
the mutual migration of the crystalline interfaces from one material to another assisted by a continuous dynamic
recrystallization process was identified as the main adhesive mechanism at the junction zone. The latter led to
successful cohesion between the rubbing surfaces. Once the reciprocating motion stopped, fast cooling caused
both materials to experience either a βlean→α′ or βlean→βmetastable transformation in the interfacial zone depending
on their local chemical composition. The limited process time and the subsequent hindered chemical
homogenization at the transition zone led to retaining the so-called intermingled α’/βm subgrains constituting
the border between both Ti-alloys.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 2.714
DOI: 10.1016/j.matchar.2019.109942
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“Triple ion beam cutting of diamond/Al composites for interface characterization”. Ji G, Tan Z, Shabadi R, Li Z, Grünewald W, Addad A, Schryvers D, Zhang D, Materials characterization 89, 132 (2014). http://doi.org/10.1016/j.matchar.2014.01.008
Abstract: A novel triple ion beam cutting technique was employed to prepare high-quality surfaces of diamond/Al composites for interfacial characterization, which has been unachievable so far. Near-perfect and artifact-free surfaces were obtained without mechanical pre-polishing. Hence, the as-prepared surfaces are readily available for further study and also, ready to be employed in a focus ion beam system for preferential selection of transmission electron microscopy samples. Dramatically different diamond/Al interface configurations – sub-micrometer Al2O3 particles and clean interfaces were unambiguously revealed.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.714
Times cited: 9
DOI: 10.1016/j.matchar.2014.01.008
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“Heterogeneous interfacial chemical nature and bonds in a W-coated diamond/Al composite”. Ji G, Tan Z, Lu Y, Schryvers D, Li Z, Zhang D, Materials characterization 112, 129 (2016). http://doi.org/10.1016/j.matchar.2015.12.013
Abstract: Heterogeneous Al/Al4C3/Al2O3/diamond{111}, Al/nanolayered Al4C3/diamond{111} and Al12W particle/Al4C3/Al2O3/diamond{111} multi-interfaces have been developed at the nanoscale in a W-coated diamond/Al composite produced by vacuum hot pressing. The formation of nanoscale Al4C3 crystals is strongly associated with local O enrichment and can be further promoted by Al12W interfacial particles. The latter effectively contributes to enhance interfacial chemical bonding reducing interfacial thermal resistance and, in turn, enhancing thermal conductivity.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 2.714
Times cited: 7
DOI: 10.1016/j.matchar.2015.12.013
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“Martensite crystallography and chemistry in dual phase and fully martensitic steels”. Du C, Hoefnagels JPM, Kolling S, Geers MGD, Sietsma J, Petrov R, Bliznuk V, Koenraad PM, Schryvers D, Amin-Ahmadi B, Materials characterization 139, 411 (2018). http://doi.org/10.1016/j.matchar.2018.03.011
Abstract: Lath martensite is important in industry because it is the key strengthening component in many advanced high strength steels. The study of crystallography and chemistry of lath martensite is extensive in the literature, however, mostly based on fully martensitic steels. In this work, lath martensite in dual phase steels is investigated with a focus on the substructure identification of the martensite islands and microstructural bands using electron backscattered diffraction, and on the influence of the accompanied tempering process during industrial coating process on the distribution of alloying elements using atom probe tomography. Unlike findings for the fully martensitic steels, no martensite islands with all 24 Kurdjumov-Sachs variants have been observed. Almost all martensite islands contain only one main packet with all six variants and minor variants from the remaining three packets of the same prior austenite grain. Similarly, the martensite bands are typically composed of connected domains originating from prior austenite grains, each containing one main packets (mostly with all variants) and few separate variants. The effect of tempering at similar to 450 degrees C (due to the industrial zinc coating process) has also been investigated. The results show a strong carbon partitioning to lath boundaries and Cottrell atmospheres at dislocation core regions due to the thermal process of coating. In contrast, auto-tempering contributes to the carbon redistribution only in a limited manner. The substitutional elements are all homogenously distributed. The phase transformation process has two effects on the material: mechanically, the earlier-formed laths are larger and softer and therefore more ductile (as revealed by nanoindentation); chemically, due to the higher dislocation density inside the later-formed laths, which are generally smaller, carbon Cottrell atmospheres are predominantly observed.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 2.714
DOI: 10.1016/j.matchar.2018.03.011
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“Microscopic investigation of as built and hot isostatic pressed Hastelloy X processed by Selective Laser Melting”. Pourbabak S, Montero-Sistiaga ML, Schryvers D, Van Humbeeck J, Vanmeensel K, Materials characterization 153, 366 (2019). http://doi.org/10.1016/j.matchar.2019.05.024
Abstract: Microstructural characteristics of Hastelloy X produced by Selective Laser Melting have been investigated by various microscopic techniques in the as built (AB) condition and after hot isostatic pressing (HIP). At sub-grain level the AB material consists of columnar high density dislocation cells while the HIP sample consists of columnar sub-grains with lower dislocation density that originate from the original dislocation cells, contradicting existing models. The sub-grains contain nanoscale precipitates enriched in Al, Ti, Cr and O, located at sub-grain boundaries in the AB condition and within the grains after HIP. At some grain boundaries, micrometer sized chromium carbides are detected after HIP. Micro hardness within the grains was found to decrease after HIP, which was attributed to the decrease in dislocation density due to recovery annealing.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 2.714
Times cited: 2
DOI: 10.1016/j.matchar.2019.05.024
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“Microstructure of adiabatic shear bands in Ti6Al4V”. Peirs J, Tirry W, Amin-Ahmadi B, Coghe F, Verleysen P, Rabet L, Schryvers D, Degrieck J, Materials characterization 75, 79 (2013). http://doi.org/10.1016/j.matchar.2012.10.009
Abstract: Microstructural deformation mechanisms in adiabatic shear bands in Ti6Al4V are studied using traditional TEM and selected area diffraction, and more advanced microstructural characterisation techniques such as energy dispersive X-ray spectroscopy, high angle annular dark field STEM and conical dark field TEM. The shear bands under investigation are induced in Ti6Al4V samples by high strain rate compression of cylindrical and hat-shaped specimens in a split Hopkinson pressure bar setup. Samples from experiments interrupted at different levels of deformation are used to study the evolution of the microstructure in and nearby the shear bands. From the early stages of adiabatic shear band formation, TEM revealed strongly elongated equiaxed grains in the shear band. These band-like grains become narrower towards the centre of the band and start to fraction even further along their elongated direction to finally result in a nano-crystalline region in the core. In fully developed shear bands, twins and a needle-like martensite morphology are observed near the shear band.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.714
Times cited: 56
DOI: 10.1016/j.matchar.2012.10.009
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“Quantitative measurement for the microstructural parameters of nano-precipitates in Al-Mg-Si-Cu alloys”. Li K, Idrissi H, Sha G, Song M, Lu J, Shi H, Wang W, Ringer SP, Du Y, Schryvers D, Materials characterization 118, 352 (2016). http://doi.org/10.1016/j.matchar.2016.06.007
Abstract: Size, number density and volume fraction of nano-precipitates are important microstructural parameters controlling the strengthening of materials. In this work a widely accessible, convenient, moderately time efficient method with acceptable accuracy and precision has been provided for measurement of volume fraction of nano-precipitates in crystalline materials. The method is based on the traditional but highly accurate technique of measuring foil thickness via convergent beam electron diffraction. A new equation is proposed and verified with the aid of 3-dimensional atom probe (3DAP) analysis, to compensate for the additional error resulted from the hardly distinguishable contrast of too short incomplete precipitates cut by the foil surface. The method can be performed on a regular foil specimen with a modem LaB6 or field-emission-gun transmission electron microscope. Precisions around +/- 16% have been obtained for precipitate volume fractions of needle-like beta ''/C and Q precipitates in an aged Al-Mg-Si-Cu alloy. The measured number density is dose to that directly obtained using 3DAP analysis by a misfit of 45%, and the estimated precision for number density measurement is about +/- 11%. The limitations of the method are also discussed.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 2.714
Times cited: 9
DOI: 10.1016/j.matchar.2016.06.007
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“Quantitative study of particle size distribution in an in-situ grown Al-TiB2 composite by synchrotron X-ray diffraction and electron microscopy”. Tang Y, Chen Z, Borbely A, Ji G, Zhong SY, Schryvers D, Ji V, Wang HW, Materials characterization 102, 131 (2015). http://doi.org/10.1016/j.matchar.2015.03.003
Abstract: Synchrotron X-ray diffraction and transmission electron microscopy (TEM) were applied to quantitatively characterize the average particle size and size distribution of free-standing TiB2 particles and TiB2 particles in an insitu grown Al–TiB2 composite. The detailed evaluations were carried out by X-ray line profile analysis using the restrictedmoment method and multiplewhole profile fitting procedure (MWP). Both numericalmethods indicate that the formed TiB2 particles are well crystallized and free of crystal defects. The average particle size determined from different Bragg reflections by the restricted moment method ranges between 25 and 55 nm, where the smallest particle size is determined using the 110 reflection suggesting the highest lateral-growth velocity of (110) facets. TheMWP method has shown that the in-situ grown TiB2 particles have a very low dislocation density (~1011 m−2) and their size distribution can be described by a log-normal distribution. Good agreement was found between the results obtained from the restricted moment and MWP methods, which was further confirmed by TEM.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 2.714
Times cited: 41
DOI: 10.1016/j.matchar.2015.03.003
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“Twinning in pure Ti subjected to monotonic simple shear deformation”. Tirry W, Bouvier S, Benmhenni N, Hammami W, Habraken AM, Coghe F, Schryvers D, Rabet L, Materials characterization 72, 24 (2012). http://doi.org/10.1016/j.matchar.2012.07.001
Abstract: The aim of this paper is to provide a thorough study on the occurrence and importance of deformation twinning in simple shear deformed pure α-Ti. A statistically relevant inspection of the morphology of the deformation twins in relation to the applied strain/deformation is performed. The investigated microstructural aspects are the twin volume fraction, the twin thickness distribution and the resolved shear stress distribution on the twin plane. All these aspects are examined as a function of the twin types and two initial textures. Monotonic simple shear experiments are carried out for three different loading directions with respect to a direction linked to the initial crystallographic texture. EBSD and TEM observations reveal the presence of View the MathML source and View the MathML source twins. The statistical analysis reveals that View the MathML source and View the MathML source twins have a similar average thickness around 1.9 nm, but the View the MathML source twins show a far larger spread on their thickness and can grow to almost the size of the original parent grain. Correlation of the twin fractions with the RSS analysis shows that RSS is an acceptable method explaining the difference in twin fractions for different textures and orientations. A detailed analysis shows that View the MathML source twins occur in average with a smaller volume fraction but with a higher RSS, indicating they are more difficult to nucleate or grow compared to View the MathML source twinning. In general a higher RSS value on the twin plane is not connected to a higher twin thickness; only in the case of View the MathML source twins the highest RSS values show clearly thicker twins.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.714
Times cited: 25
DOI: 10.1016/j.matchar.2012.07.001
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“A quantitative method to characterize the Al4C3-formed interfacial reaction: the case study of MWCNT/Al composites”. Yan L, Tan Z, Ji G, Li Z, Fan G, Schryvers D, Shan A, Zhang D, Materials characterization 112, 213 (2015). http://doi.org/10.1016/j.matchar.2015.12.031
Abstract: The Al4C3-formed interfacial reaction plays an important role in tuning the mechanical and thermal properties of carbon/aluminum (C/Al) composites reinforced with carbonaceous materials such as multi-wall carbon nanotube (MWCNT) and graphene nanosheet. In terms of the hydrolysis nature of Al4C3, an electrochemical dissolution method was developed to quantitatively characterize the extent of C/Al interfacial reaction, which involves dissolving the composite samples in alkaline solution first, then collecting and measuring the CH4 gas released by Al4C3 hydrolysis with a gas chromatograph. Through a case study with powder metallurgy fabricated 2.0 wt.% MWCNT/Al composites, the detectability limit of the proposed method is 0.4 wt.% Al4C3, corresponding to 5 % extent of interfacial reaction with a measurement error of ±3 %. And then, with the already known MWCNT/Al reaction extent vs different sintering temperature and time, the reaction kinetics with an activation energy of 281 kJ mol-1 was successfully derived. Therefore, this rapid, sensitive, accurate method supplies an useful tool to optimize the processing and properties of all kinds of C/Al composites via interface design/control.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 2.714
Times cited: 24
DOI: 10.1016/j.matchar.2015.12.031
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“Atomic-resolution interfacial structures and diffusion kinetics in Gd/Bi0.5Sb1.5Te3 magnetocaloric/thermoelectric composites”. Wei P, Ke B, Xing L, Li C, Ma S, Nie X, Zhu W, Sang X, Zhang Q, Van Tendeloo G, Zhao W, Materials Characterization 163, 110240 (2020). http://doi.org/10.1016/J.MATCHAR.2020.110240
Abstract: The demand of a full solid-state cooling technology based on magnetocaloric and thermoelectric effects has led to a growing interest in screening candidate materials with high-efficiency cooling performance, which also stimulates the exploration of magnetocaloric/thermoelectric hybrid cooling materials. A series of Gd/Bi0.5Sb1.5Te3 composites was fabricated in order to develop the hybrid cooling technology. The chemical composition, phase structure and diffusion kinetics across the reaction layers in Gd/Bi0.5Sb1.5Te3 composites were analyzed at different reaction temperatures. Micro-area elemental analysis indicates that the formation of interfacial phases is dominated by the diffusion of Gd and Te while the diffusion of Bi and Sb is impeded. The interfacial phases, including GdTe2, GdTe3, and intermediate phases GdTex, are identified by atomic-resolution electron microscopy. The concentration modulation of Gd and Te is adapted by altering the stacking of the Te square-net sheets and the corrugated GdTe sheets. Boltzmann-Marano analysis was applied to reveal the diffusion kinetics of Gd and Te in the interfacial layers. The diffusion coefficients of Te in GdTe2 and GdTe3 are much higher than that of Gd while in GdTe the situation is reversed. This study provides a clear picture to understand the interfacial phase structures down to an atomic scale as well as the interfacial diffusion kinetics in Gd/Bi0.5Sb1.5Te3 hybrid cooling materials.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 4.7
Times cited: 1
DOI: 10.1016/J.MATCHAR.2020.110240
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“TEM investigation of the role of the polycrystalline-silicon film/substrate interface in high quality radio frequency silicon substrates”. Ding L, Raskin J-P, Lumbeeck G, Schryvers D, Idrissi H, Materials Characterization 161, 110174 (2020). http://doi.org/10.1016/J.MATCHAR.2020.110174
Abstract: The microstructural characteristics of two polycrystalline silicon (poly-Si) films with different electrical properties produced by low-pressure chemical vapour deposition on top of high resistivity silicon substrates were investigated by advanced transmission electron microscopy (TEM), including high resolution aberration corrected TEM and automated crystallographic orientation mapping in TEM. The results reveal that the nature of the poly-Si film/Si substrate interface is the main factor controlling the electrical resistivity of the poly-Si films. The high resistivity and high electrical linearity of poly-Si films are strongly promoted by the Sigma 3 twin type character of the poly-Si/Si substrate interface, leading to the generation of a huge amount of extended defects including stacking faults, Sigma 3 twin boundaries as well as Sigma 9 grain boundaries at this interface. Furthermore, a high density of interfacial dislocations has been observed at numerous common and more exotic grain boundaries deviating from their standard crystallographic planes. In contrast, poly-Si film/Si substrate interfaces with random character do not favour the formation of such complex patterns of defects, leading to poor electrical resistivity of the poly-Si film. This finding opens windows for the development of high resistivity silicon substrates for Radio Frequency (RF) integrated circuits (ICs) applications.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 4.7
DOI: 10.1016/J.MATCHAR.2020.110174
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“Structures in textured Cu-Al-Ni shape memory thin films grown by sputtering”. Espinoza Torres C, Condó, AM, Haberkorn N, Zelaya E, Schryvers D, Guimpel J, Lovey FC, Materials characterization 96, 256 (2014). http://doi.org/10.1016/j.matchar.2014.08.005
Abstract: The structure and texture formation in CuAlNi thin films of different thicknesses (1 μm to 5 μm) grown by DC magnetron sputtering without any intentional heating of the substrate are reported. The as-grown films present grains with an average size of 20 nm. The films with thickness of 1 μm have a single metastable phase with a hexagonal structure and are textured with planes (0002) parallel to the plane of the films. It was observed that thicker films present phase coexistence between metastable hexagonal and body centered cubic structures with a gradual increment of the body centered cubic phase fraction. The films with thickness of 5 μm are textured with planes (0002) and View the MathML source101¯0 in the hexagonal structure, whereas in the body centered cubic structure the films are textured with {110} planes parallel to the plane of the films. This fact can be associated with self-heating of the substrate during the growth of the films and with the relative stability of the metastable phases. Free standing films annealed in a second step (1123 K for 1 h) present austenitic phase with L21 structure and sub-micrometric grains textured with {220}L21 planes parallel to the plane of the films. The martensitic transformation temperature was determined from the analysis of resistance against temperature measurements.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.714
Times cited: 9
DOI: 10.1016/j.matchar.2014.08.005
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“Quantitative FIB/SEM three-dimensional characterization of a unique Ni₄Ti₃, network in a porous Ni50.8Ti49.2 alloy undergoing a two-step martensitic transformation”. Cao S, Zeng CY, Li YY, Yao X, Ma X, Samaee V, Schryvers D, Zhang XP, Materials Characterization 169, 110595 (2020). http://doi.org/10.1016/J.MATCHAR.2020.110595
Abstract: The three-dimensional (3D) nanostructure of Ni4Ti3 precipitates in a porous Ni50.8Ti49.2 alloy has been re-constructed by “Slice-and-View” in a Focused Ion Beam/Scanning Electron Microscope (FIB/SEM). The 3D configuration of these precipitates forming a network structure in the B2 austenite matrix has been characterized via 3D visualization and quantitative analysis including volume fraction, skeleton, degree of anisotropy and local thickness. It is found that dense Ni4Ti3 precipitates occupy 54% of the volume in the B2 austenite matrix. Parallel Ni4Ti3 precipitates grow alongside the surface of a micro-pore, yielding an asymmetric structure, while nano voids do not seem to affect the growth of Ni4Ti3 precipitates. The small average local thickness of the precipitates around 60 nm allows their coherency with the matrix, and further induces the R-phase transformation in the matrix. On the other hand, the B2 matrix exhibits a winding and narrow structure with a skeleton of 18.20 mm and a thickness similar to the precipitates. This discontinuous matrix segmented by the Ni4Ti3 network and pores is responsible for the gradual transformation by stalling the martensite propagation.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 4.7
DOI: 10.1016/J.MATCHAR.2020.110595
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“Early stages of dissolution corrosion in 316L and DIN 1.4970 austenitic stainless steels with and without anticorrosion coatings in static liquid lead-bismuth eutectic (LBE) at 500 degrees C”. Charalampopoulou E, Lambrinou K, Van der Donck T, Paladino B, Di Fonzo F, Azina C, Eklund P, Mraz S, Schneider JM, Schryvers D, Delville R, Materials Characterization 178, 111234 (2021). http://doi.org/10.1016/J.MATCHAR.2021.111234
Abstract: This work addresses the early stages (<= 1000 h) of the dissolution corrosion behavior of 316L and DIN 1.4970 austenitic stainless steels in contact with oxygen-poor (C-O < 10(-8) mass%), static liquid lead-bismuth eutectic (LBE) at 500 degrees C for 600-1000 h. The objective of this study was to determine the relative early-stage resistance of the uncoated steels to dissolution corrosion and to assess the protectiveness of select candidate coatings (Cr2AlC, Al2O3, V2AlxCy). The simultaneous exposure of steels with intended differences in microstructure and thermomechanical state showed the effects of steel grain size, density of annealing/deformation twins, and secondary precipitates on the steel dissolution corrosion behavior. The findings of this study provide recommendations on steel manufacturing with the aim of using the steels to construct Gen-IV lead-cooled fast reactors.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 2.714
DOI: 10.1016/J.MATCHAR.2021.111234
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“Microstructure and phase composition characterization in a Co38Ni33Al29 ferromagnetic shape memory alloy”. Lu JB, Schryvers D, Materials characterization 118, 9 (2016). http://doi.org/10.1016/j.matchar.2016.04.028
Abstract: Transmission electron microscopy was performed to investigate the microstructures of a secondary phase and its surrounding matrix in a Co38Ni33Al29 ferromagnetic shape memory alloy. The secondary phase shows a γ′ L12 structure exhibiting a dendritic morphology with enclosed B2 austenite regions while the matrix shows the L10 martensitic structure. A secondary phase-austenite-martensite sandwich structure with residual austenite ranging from several hundred nanometers to several micrometers wide is observed at the secondary phase-martensite interface due to the depletion of Co and enrichment of Al in the chemical gradient zone and the effect of the strong martensitic start temperature dependency of the element concentrations. The crystallographic orientation relationship of the secondary phase and the B2 austenite fits the Kurdjumov-Sachs relationship.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 2.714
Times cited: 3
DOI: 10.1016/j.matchar.2016.04.028
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