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Publications
Publications (42)
The effects of the secondary processes of Hot Isostatic Pressing (HIP) at 920 °C and Heat Treatment (HT) at 1000 °C of Electron Beam-Melted (EBM) Ti–6Al–4V alloy on the microstructure and hydrogen embrittlement (HE) after electrochemical hydrogen charging (EC) were investigated. Comprehensive characterization, including microstructural analysis, X-...
Electron Beam Additive Manufacturing (EBAM) is a powder bed-based Additive Manufacturing (AM) technology, considered to be an innovative industrial production technology. EBM employs an electron beam in a vacuum environment to selectively melt a metallic powder bed directed by a computer aided design (CAD) model. Although it is generally assumed th...
Additive manufacturing is a novel and breakthrough technology by which parts can be manufactured for various purposes and services. As in any production process, the desired properties of additively manufactured components, particularly in electron beam melting processes, ultimately depend on the manufacturing process parameters. Process parameters...
Effective optimization of the production of Ti-6Al-4V using AM requires a fundamental understanding of the relative importance of different microstructural features to the deformation and failure mechanisms, particularly features that vary between production methods. In this study, the tensile response and deformation mechanisms of electron beam me...
The influence of electrochemical charging of hydrogen at j = −5 mA/cm² for 6, 12, 48 and 96 h on the structural and the mechanical behavior of wrought and electron beam melting (EBM) Ti–6Al–4V alloys containing 6 wt% β and similar impurities level was investigated. The length of the α/β interphase boundaries in the EBM alloy was larger by 34% compa...
Among various off-equilibrium microstructures of additively manufactured Ti-6Al-4V alloy, electron beam powder bed fusion, in which three dimensional metallic objects are fabricated by melting the ingredient powder materials layer by layer on a pre-heated bed, results in a specimen that is nearly free of the preferred orientation of the α-Ti phase...
Thermal decomposition of titanium hydrides in electrochemically hydrogenated electron beam melting (EBM) and wrought Ti–6Al–4V alloys containing 6 wt% β is compared. Differential scanning calorimetry (DSC) is used to identify phase transitions. High-temperature X-ray diffraction (HTXRD) is used to identify phases and determine their contents and cr...
Electron beam melting (EBM) is a metal powder bed fusion additive manufacturing (AM) technology that facilitates the production of metal parts by selectively melting areas in layers of metal powder. The electron beam melting process is conducted in a vacuum chamber environment regulated with helium (He) at a pressure on the scale of 10−3 mbar. One...
Additively-manufactured Ti-6Al-4V (Ti64) exhibits high strength but in some cases inferior elongation to those of conventionally manufactured materials. Post-processing of additively manufactured Ti64 components is investigated to modify the mechanical properties for specific applications while still utilizing the benefits of the additive manufactu...
Electron beam powder bed fusion, commonly termed electron beam melting (EBM), offers great versatility in multiple-part processes and can produce high quality as-built components due to low residual stresses. The EBM process is complex and requires careful thermal management, including uniform and consistent preheating of the powder bed, in order t...
The hydrogen behavior in electrochemically charged electron beam melting (EBM) and wrought Ti–6Al–4V alloys with a similar β-phase content of ~6 wt% was compared. Hydrogenation resulted in the formation of microvoids, either adjacent to the surface or along interphases, their coalescence, and emanation of microcracks around them. The microstructure...
Knowledge of the appearance of texture components and fibres in pole figures, in inverse pole figures and in Euler space is fundamental for texture analysis. For cubic crystal systems, such as steels, an extensive literature exists and, for example, the book by Matthies, Vinel & Helming [Standard Distributions in Texture Analysis: Maps for the Case...
Using an electron beam melting (EBM) printing machine (Arcam A2X, Sweden), a matrix of 225 samples (15 rows and 15 columns) of Ti-6Al-4V was produced. The density of the specimens across the tray in the as-built condition was approximately 99.9% of the theoretical density of the alloy, ρ T. Tensile strength, tensile elongation, and fatigue life wer...
The electron inelastic mean free path (IMFP) is commonly used in surface analysis techniques such as X-ray photoelectron spectroscopy. Though numerous studies have been conducted in the quest to define the IMFP value, it is still substantiated mainly on the basis of calculations and extrapolations. Experimental methods such as elastic peak electron...
This study presents a detailed characterization of room temperature bulk microstructure and texture of additively manufactured Ti-6Al-4V alloy samples with the neutron time-of-flight diffractometer HIPPO. A comparison is made between samples that were manufactured by two different methods utilizing selective laser melting and electron beam melting....
Characterization of the bulk microstructure using neutron diffraction has been applied to investigate the phase fractions and textures of α- and β-phases in Ti-6Al-4V fabricated by additive manufacturing. The microstructure of a specimen cut from a fan structure, built by either electron beam melting (EBM) or selective laser melting, indicated that...
Pulse-echo ultrasonic method was carried out to investigate possible anisotropy in selective laser melting additively manufactured (AM) AlSi10Mg samples. Three types of ultrasonic analyses were employed: time of flight (TOF) sound velocity measurement, frequency depended attenuation and exponential fitted attenuation. Analysis of the transverse wav...
Pulse-echo ultrasonic method was carried out to investigate possible anisotropy in selective laser melting additively manufactured (AM) AlSi10Mg samples. Three types of ultrasonic analyses were employed: time of flight (TOF) sound velocity measurement, frequency depended attenuation and exponential fitted attenuation. Analysis of the transverse wav...
Additive Manufacturing (AM) of Ti6Al4V alloy by Electron Beam Melting (EBM)
yields unique microstructures characterized by micron and sub-micron grains.
Phase content is primarily α-phase and residual β-phase. For the research of
mechanical properties of AM Ti6Al4V, specimens in the as built (AB), heat
treatment (HT), and hot isostatic pressing (HI...
Outline Introduction Application of AM of metals Maturity (MRL and other approaches) Our methodology (Engineering and Scientific) DT, NDT and NDE Ti6Al4V-EBM (strength, fatigue, NDT)
This Invention relates to radiation measurement instrumentation for monitoring the local neutron flux inside the core of a nuclear reactor and for evaluation of the absorbed dose in Radio-Isotope production processes. In particular, the invention relates to simultaneous measurement of neutron and gamma flux inside the reactor core and its surroundi...
The use of additive manufacturing (AM) by Electron Beam Melting (EBM) or Selective Laser Melting (SLM) has extensively grown in the past few years. A major goal in AM is to manufacture materials with mechanical properties at least as good as traditionally manufactured materials. In this work we present the results of planar impact tests and Split H...
Heating a mixture of uranyl(vi) nitrate and tantalum(v) oxide in the molar ratio of 2 : 3 to 1400 °C resulted in the formation of a new compound, UTa3O10. The honey colored to yellow brown crystals of UTa3O10 crystallize in an orthorhombic structure with the space group Fddd (no. 70), lattice parameters a = 7.3947(1), b = 12.7599(2), c = 15.8156(2)...
Although pentavalent uranium can exist in aqueous solution, its presence in the solid state is uncommon. Metal monouranates, MgUO4, CrUO4 and FeUO4 were synthesized for detailed structural and energetic investigations. Structural characteristics of these uranates used powder X-ray diffraction, synchrotron X-ray absorption spectroscopy, X-ray photoe...
Neutron diffraction study of poly-crystalline bulk samples of Ti-6Al-4V, prepared using laser selective melting (SLM) and electron beam melting (EBM), and of their ingredient powders, is reported. Both the SLM and EBM samples do not contain the macro- and micro-strain, found in the ingredient powder particles. In addition, the micro-structure of th...
In this paper, the mechanical properties and fracture behavior of additive manufactured AlSi10Mg specimens were investigated. The samples were manufactured by the powder-bed process known as Selective Laser Melting and underwent machining afterwards. Nine samples were tested in the as-built condition, as well as after stress relief heat treatment a...
Nanoscale uranyl peroxide clusters containing UO2 (2+) groups bonded through peroxide bridges to form polynuclear molecular species (polyoxometalates) exist both in solution and in the solid state. There is an extensive family of clusters containing 28 uranium atoms (U28 clusters), with an encapsulated anion in the center, for example, [UO2 (O2 )3-...
Weighing in… on uranyl phase stability. Two uranyl polyoxometalates that differ only by the anion encapsulated in the center are assessed by computational and experimental methods. Thermodynamic and molecular-orbital calculations agree that stability is gained by increasing cation/anion interactions. This agrees with the trend of all uranyl phases...
Defining the properties of the powder used for metal-based additive manufacturing (AM), is a necessary condition for the industry to be able to confidently select a suitable powder and produce consistent parts with known and predictable properties. This article reports results for AlSi10Mg powder properties assessment. The particle size, morphology...
Sintering of nanocrystalline (nc) monoclinic yttrium oxide (Y 2 O 3) was studied in the homologue temperature range of 0.4–0.7T M . Samples were isostatically consolidated at super high pressure (SHP), up to 1.8 GPa. The combined effects of consolidation pressure and sintering temperature on the properties and microstructure are explored. The physi...
Layer thickness estimation method using the average energy shift of electrons passing through the layer is presented. The traditional approach of analyzing the signal electron is extended by using the spectral distribution of the energy shift of the electrons. In this approach, the tendency of the multiple inelastic scattering spectra to increase t...
Lanthanide sesquioxides (Ln2O3) display three stable solid phases as a function of temperature. It has been assumed that Y2O3 should display similar crystal structures and phase transitions as other Ln2O3. Recently a new phase transition sequence was reported for Y2O3, contradicting earlier studies. In this work Y2O3 was found to have the same phas...
The initial room-temperature interactions of water vapor with polycrystalline bulk annealed uranium surfaces were studied by combined measurements utilizing Direct Recoil Spectrometry (DRS) and X-ray Photoelectron Spectroscopy (XPS). It was found that the water goes through a complete dissociation into oxidic oxygen and two neutral H atoms througho...
Traces of about 2% water vapor are sufficient to inhibit hydrogen dissociation and chemisorption on uranium surfaces, under low pressure exposures, at room temperature. The efficiency of the inhibition increases with temperature in the range of 200 – 400K. The inhibition effect is also influenced by the extent of residual strain of the sample, with...
The initial interaction of H2O vapor with polycrystalline uranium surfaces was studied with samples initially strained, then strain relieved by heat treatments, performed in the temperature range up to ∼650 K. The chemisorption characteristics of these surfaces were studied by a combination of direct recoils spectrometry and X-ray photoelectron spe...
The initial interaction of water vapor with polycrystalline uranium surfaces at low temperatures (LT, 200K), was studied by combined measurements utilizing Direct Recoil Spectrometry (DRS), Auger electron Spectroscopy (AES) and X-ray Photoelectron Spectroscopy (XPS). Three stages of water dissociation and adsorption can be observed: Stage (1) 0–0.6...
The initial room-temperature interactions of water vapor with polycrystalline bulk annealed uranium surfaces were studied by combined measurements utilizing direct recoil spectrometry (DRS) and X-ray photoelectron spectroscopy (XPS). It was found that the water goes through a complete dissociation into oxidic oxygen and two neutral H atoms througho...