ori yeheskel - Academia.edu (original) (raw)
Papers by ori yeheskel
Additive Manufacturing, 2022
Materials Science and Engineering, 1986
The hot isostatic pressing (HIP) of Si3N4 was performed in the temperature range 1500-1800 °C and... more The hot isostatic pressing (HIP) of Si3N4 was performed in the temperature range 1500-1800 °C and within the pressure range 90-1 72 MPa. Both additive-free Si3N 4 and Si3N 4 with Y203 additions were studied. During the HIP process the transformation of (~-SisN 4 to ~3-Si3N 4 occurs and the amount of (~-+ ~3 transformation increases as the HIP temperature and HIP pressure increase. The-+ {3 transition also depends on the Y2 03 content, The density of the SizN 4 consolidated by HIP increases as the HIP pressure, HIP temperature and Y2 0 3 content increase. The hardness and Young's modulus of the product increase gradually with increasing ]72 03. The effect of outgassing the starting material prior to HIP on the properties of the final product is discussed.
Additive Manufacturing, 2018
Abstract Pulse-echo ultrasonic method was carried out to investigate possible anisotropy in selec... more Abstract 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 waves TOF sound velocity as a function the oscillation angle relative to the build direction reveals that the AM AlSi10Mg material has anisotropy in both transverse wave velocity and attenuation with respect to the build direction. Such an anisotropy is with symmetry around the build direction. Three transverse wave velocity zones were identified, low-velocity zone, where the transverse oscillation direction perpendicular to the build direction, high-velocity zone where the transverse oscillation direction parallel to the build direction and a transition zone. This behavior held even after heat treatments. The transverse velocity and the frequency depended attenuation seems to be sensitive tools that enable detection of subtle changes in AM products.
AIP Conference Proceedings, 2009
ABSTRACT Using bulk acoustic waves we studied the nonlinear mechanical properties and hysteresis ... more ABSTRACT Using bulk acoustic waves we studied the nonlinear mechanical properties and hysteresis of the acousto-elastic effect in kinking nonlinear elastic, KNE, solids. The experiments reviewed here present direct observation of nonlinear hysteretic scattering and attenuation of ultrasonic waves in Ti3SiC2 and Ti3AlC2, representatives of KNE solids, as a function of quasi-static cyclic compressive stresses. We attribute this dynamic behavior to the interaction of the acoustic waves with dislocation in incipient kink bands. The relevance of these findings to possible sensor applications of hysteretic KNE solids is briefly discussed.
Scripta Materialia, 2011
ABSTRACT In this paper we report in situ neutron diffraction results of fine-grained (8 μm) polyc... more ABSTRACT In this paper we report in situ neutron diffraction results of fine-grained (8 μm) polycrystalline titanium sulfocarbide samples loaded to 700 MPa. The overall strains, and those on individual planes, are modeled via the elastoplastic self-consistent approach using elastic constants derived from ab initio calculations. Based on the results, we conclude that the response at stresses below 1 GPa, is, for the most part linear elastic and that when the theoretical elastic constants are combined with the elastoplastic self-consistent method, accurate predictions can be obtained of both the overall stress–strain curves and, more importantly, the 0 0 01, 101¯, and 101¯0 reflections.
Materials Science and Engineering: A, 2010
Recently cobalt was classified as a kinking nonlinear elastic, KNE, solid. Fully reversible incip... more Recently cobalt was classified as a kinking nonlinear elastic, KNE, solid. Fully reversible incipient kink bands, IKBs, were invoked to explain both its microyielding and hysteretic stress–strain curves. Herein we present further evidence and insights in the KNE nature of cobalt by measuring its mechanical hysteresis as a function of grain size, pre-strain and testing temperature. Unlike previous work, in
Journal of the European Ceramic Society, 2013
ABSTRACT Sintering of nanocrystalline (nc) monoclinic yttrium oxide (Y 2 O 3) was studied in the ... more ABSTRACT 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 physical properties of the samples, mainly elastic modulus follow in general the density changes, or the interparticle contact area, but are also affected by sintering temperature. The effect of compaction pressure and sample density on the phase transition is studied and discussed.
![Research paper thumbnail of Elastic moduli of polycrystalline LaAl[sub x]Ni[sub 5−x]](https://attachments.academia-assets.com/83465970/thumbnails/1.jpg)
](Journal of Applied Physics, 2002
Journal of Alloys and Compounds, 2004
Applied Physics Letters, 2009
Herein we report on direct experimental observation of nonlinear hysteretic ultrasonic wave trans... more Herein we report on direct experimental observation of nonlinear hysteretic ultrasonic wave transmission through the kinking nonlinear elastic solids Ti 3 SiC 2 and Ti 3 AlC 2 under bias-stress loading. We observed two characteristic regimes; up to strain Ϸ2 ϫ 10 −4 , the ultrasound attenuation increased strongly and linearly with strain. At higher strains, the attenuation was fully reversible and hysteretic as the compressive stresses were cycled. This hysteretic behavior was attributed to interaction of the acoustic waves with dislocations in the incipient kink bands, the micromechanism believed to be responsible for the concomitant hysteretic stress-strain loops. The relevance of these findings to possible sensor applications is briefly discussed.
LaNi5 and its alloys are of great interest for hydrogen storage, especially for use in batteries.... more LaNi5 and its alloys are of great interest for hydrogen storage, especially for use in batteries. It is important to fully characterize these materials, including their elastic properties. Ingots of LaSn_xNi_5-x ( x = 0.1, 0.22, 0.4, and 0.5) were prepared by arc-melting the elemental constituents. The ingots were then ground into powders. These intermetallic powders were then subjected to hot isostatic pressing ( 1000 bar at 1050 ^oC for 2 h). The high pressure/high temperature treatment transformed the powders into solid materials, which had near theoretical densities. Resonant ultrasound spectroscopy and conventional ultrasonic pulse echo techniques were used to measure the elastic constants. Comparing the results with the moduli of LaNi5 previously measured showed that both the bulk modulus and the shear modulus decrease with increasing x. The porosity-corrected bulk and shear moduli decrease from 139.6 GPa and 59.2 GPa respectively for x = 0 to 129.0 GPa and 54.4 GPa respectively for x = 0.5. These results should be useful in understanding the elastic energy contribution to hydride formation.
Materials, 2019
Using an electron beam melting (EBM) printing machine (Arcam A2X, Sweden), a matrix of 225 sample... more 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, ρT. Tensile strength, tensile elongation, and fatigue life were studied for the as-built samples. Location dependency of the mechanical properties along the build area was observed. Hot isostatic pressing (HIP) slightly increased the density to 99.99% of ρT but drastically improved the fatigue endurance and tensile elongation, probably due to the reduction in the size and the distribution of flaws. The microstructure of the as-built samples contained various defects (e.g., lack of fusion, porosity) that were not observed in the HIP-ed samples. HIP also reduced some of the location related variation in the mechanical properties values, observed in the as-printed condition.
Materials
Additively-manufactured Ti-6Al-4V (Ti64) exhibits high strength but in some cases inferior elonga... more 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 manufacturing process. The mechanical properties and fatigue resistance of Ti64 samples made by electron beam melting were tested in the as-built state. Several heat treatments (up to 1000 °C) were performed to study their effect on the microstructure and mechanical properties. Phase content during heating was tested with high reliability by neutron diffraction at Los Alamos National Laboratory. Two different hot isostatic pressings (HIP) cycles were tested, one at low temperature (780 °C), the other is at the standard temperature (920 °C). The results show that lowering the HIP holding temperature retains the fine microstructure (~1% β phase) and ...
Lanthanide sesquioxides (Ln2O3) display three stable solid phases as a function of temperature. I... more 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 phase transition sequence as other lanthanide sesquioxides (Ln2O3). Additionally, in this study increasing external pressure has been found to have a similar effect to increasing temperature on crystal structure in Y2O3. At room temperature the first pressure-induced phase transition occured at ~13 GPa, in which the symmetry changed from cubic to monoclinic symmetry. The symmetry then changed from monoclinic to hexagonal at 24.5 GPa. The sequence of phase transitions was not reversible upon pressure release. With decreasing pressure only a single phase transition occurred, from hexagonal to monoclinic symmetry.
JOM
Characterization of the bulk microstructure using neutron diffraction has been applied to investi... more 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 predominantly the build direction and not the fan angle determines the microstructure. In situ heating experiments of specimens from a rod built using EBM provided insight into the lattice strain, phase fraction, and texture evolution, providing a rich picture of the microstructure changes during heat treatment of additively manufactured Ti-6Al-4V. A remarkably low weight fraction of β-phase at lower temperatures, deviations from thermal expansion behavior attributed to vanadium repartitioning, as well as texture strengthening were observed.
Additive Manufacturing, 2022
Materials Science and Engineering, 1986
The hot isostatic pressing (HIP) of Si3N4 was performed in the temperature range 1500-1800 °C and... more The hot isostatic pressing (HIP) of Si3N4 was performed in the temperature range 1500-1800 °C and within the pressure range 90-1 72 MPa. Both additive-free Si3N 4 and Si3N 4 with Y203 additions were studied. During the HIP process the transformation of (~-SisN 4 to ~3-Si3N 4 occurs and the amount of (~-+ ~3 transformation increases as the HIP temperature and HIP pressure increase. The-+ {3 transition also depends on the Y2 03 content, The density of the SizN 4 consolidated by HIP increases as the HIP pressure, HIP temperature and Y2 0 3 content increase. The hardness and Young's modulus of the product increase gradually with increasing ]72 03. The effect of outgassing the starting material prior to HIP on the properties of the final product is discussed.
Additive Manufacturing, 2018
Abstract Pulse-echo ultrasonic method was carried out to investigate possible anisotropy in selec... more Abstract 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 waves TOF sound velocity as a function the oscillation angle relative to the build direction reveals that the AM AlSi10Mg material has anisotropy in both transverse wave velocity and attenuation with respect to the build direction. Such an anisotropy is with symmetry around the build direction. Three transverse wave velocity zones were identified, low-velocity zone, where the transverse oscillation direction perpendicular to the build direction, high-velocity zone where the transverse oscillation direction parallel to the build direction and a transition zone. This behavior held even after heat treatments. The transverse velocity and the frequency depended attenuation seems to be sensitive tools that enable detection of subtle changes in AM products.
AIP Conference Proceedings, 2009
ABSTRACT Using bulk acoustic waves we studied the nonlinear mechanical properties and hysteresis ... more ABSTRACT Using bulk acoustic waves we studied the nonlinear mechanical properties and hysteresis of the acousto-elastic effect in kinking nonlinear elastic, KNE, solids. The experiments reviewed here present direct observation of nonlinear hysteretic scattering and attenuation of ultrasonic waves in Ti3SiC2 and Ti3AlC2, representatives of KNE solids, as a function of quasi-static cyclic compressive stresses. We attribute this dynamic behavior to the interaction of the acoustic waves with dislocation in incipient kink bands. The relevance of these findings to possible sensor applications of hysteretic KNE solids is briefly discussed.
Scripta Materialia, 2011
ABSTRACT In this paper we report in situ neutron diffraction results of fine-grained (8 μm) polyc... more ABSTRACT In this paper we report in situ neutron diffraction results of fine-grained (8 μm) polycrystalline titanium sulfocarbide samples loaded to 700 MPa. The overall strains, and those on individual planes, are modeled via the elastoplastic self-consistent approach using elastic constants derived from ab initio calculations. Based on the results, we conclude that the response at stresses below 1 GPa, is, for the most part linear elastic and that when the theoretical elastic constants are combined with the elastoplastic self-consistent method, accurate predictions can be obtained of both the overall stress–strain curves and, more importantly, the 0 0 01, 101¯, and 101¯0 reflections.
Materials Science and Engineering: A, 2010
Recently cobalt was classified as a kinking nonlinear elastic, KNE, solid. Fully reversible incip... more Recently cobalt was classified as a kinking nonlinear elastic, KNE, solid. Fully reversible incipient kink bands, IKBs, were invoked to explain both its microyielding and hysteretic stress–strain curves. Herein we present further evidence and insights in the KNE nature of cobalt by measuring its mechanical hysteresis as a function of grain size, pre-strain and testing temperature. Unlike previous work, in
Journal of the European Ceramic Society, 2013
ABSTRACT Sintering of nanocrystalline (nc) monoclinic yttrium oxide (Y 2 O 3) was studied in the ... more ABSTRACT 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 physical properties of the samples, mainly elastic modulus follow in general the density changes, or the interparticle contact area, but are also affected by sintering temperature. The effect of compaction pressure and sample density on the phase transition is studied and discussed.
Journal of Applied Physics, 2002
Journal of Alloys and Compounds, 2004
Applied Physics Letters, 2009
Herein we report on direct experimental observation of nonlinear hysteretic ultrasonic wave trans... more Herein we report on direct experimental observation of nonlinear hysteretic ultrasonic wave transmission through the kinking nonlinear elastic solids Ti 3 SiC 2 and Ti 3 AlC 2 under bias-stress loading. We observed two characteristic regimes; up to strain Ϸ2 ϫ 10 −4 , the ultrasound attenuation increased strongly and linearly with strain. At higher strains, the attenuation was fully reversible and hysteretic as the compressive stresses were cycled. This hysteretic behavior was attributed to interaction of the acoustic waves with dislocations in the incipient kink bands, the micromechanism believed to be responsible for the concomitant hysteretic stress-strain loops. The relevance of these findings to possible sensor applications is briefly discussed.
LaNi5 and its alloys are of great interest for hydrogen storage, especially for use in batteries.... more LaNi5 and its alloys are of great interest for hydrogen storage, especially for use in batteries. It is important to fully characterize these materials, including their elastic properties. Ingots of LaSn_xNi_5-x ( x = 0.1, 0.22, 0.4, and 0.5) were prepared by arc-melting the elemental constituents. The ingots were then ground into powders. These intermetallic powders were then subjected to hot isostatic pressing ( 1000 bar at 1050 ^oC for 2 h). The high pressure/high temperature treatment transformed the powders into solid materials, which had near theoretical densities. Resonant ultrasound spectroscopy and conventional ultrasonic pulse echo techniques were used to measure the elastic constants. Comparing the results with the moduli of LaNi5 previously measured showed that both the bulk modulus and the shear modulus decrease with increasing x. The porosity-corrected bulk and shear moduli decrease from 139.6 GPa and 59.2 GPa respectively for x = 0 to 129.0 GPa and 54.4 GPa respectively for x = 0.5. These results should be useful in understanding the elastic energy contribution to hydride formation.
Materials, 2019
Using an electron beam melting (EBM) printing machine (Arcam A2X, Sweden), a matrix of 225 sample... more 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, ρT. Tensile strength, tensile elongation, and fatigue life were studied for the as-built samples. Location dependency of the mechanical properties along the build area was observed. Hot isostatic pressing (HIP) slightly increased the density to 99.99% of ρT but drastically improved the fatigue endurance and tensile elongation, probably due to the reduction in the size and the distribution of flaws. The microstructure of the as-built samples contained various defects (e.g., lack of fusion, porosity) that were not observed in the HIP-ed samples. HIP also reduced some of the location related variation in the mechanical properties values, observed in the as-printed condition.
Materials
Additively-manufactured Ti-6Al-4V (Ti64) exhibits high strength but in some cases inferior elonga... more 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 manufacturing process. The mechanical properties and fatigue resistance of Ti64 samples made by electron beam melting were tested in the as-built state. Several heat treatments (up to 1000 °C) were performed to study their effect on the microstructure and mechanical properties. Phase content during heating was tested with high reliability by neutron diffraction at Los Alamos National Laboratory. Two different hot isostatic pressings (HIP) cycles were tested, one at low temperature (780 °C), the other is at the standard temperature (920 °C). The results show that lowering the HIP holding temperature retains the fine microstructure (~1% β phase) and ...
Lanthanide sesquioxides (Ln2O3) display three stable solid phases as a function of temperature. I... more 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 phase transition sequence as other lanthanide sesquioxides (Ln2O3). Additionally, in this study increasing external pressure has been found to have a similar effect to increasing temperature on crystal structure in Y2O3. At room temperature the first pressure-induced phase transition occured at ~13 GPa, in which the symmetry changed from cubic to monoclinic symmetry. The symmetry then changed from monoclinic to hexagonal at 24.5 GPa. The sequence of phase transitions was not reversible upon pressure release. With decreasing pressure only a single phase transition occurred, from hexagonal to monoclinic symmetry.
JOM
Characterization of the bulk microstructure using neutron diffraction has been applied to investi... more 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 predominantly the build direction and not the fan angle determines the microstructure. In situ heating experiments of specimens from a rod built using EBM provided insight into the lattice strain, phase fraction, and texture evolution, providing a rich picture of the microstructure changes during heat treatment of additively manufactured Ti-6Al-4V. A remarkably low weight fraction of β-phase at lower temperatures, deviations from thermal expansion behavior attributed to vanadium repartitioning, as well as texture strengthening were observed.