A coupled diffusion-deformation, multiphase field model for elastoplastic materials is presented.... more A coupled diffusion-deformation, multiphase field model for elastoplastic materials is presented. The equations governing the evolution of the phase fields and the molar concentration field are derived in a thermodynamically consistent way using microforce balance laws. As an example of its capabilities, the model is used to study the growth of the intermetallic compound (IMC) Cu 6 Sn 5 during room-temperature aging. This IMC is of great importance in, e.g., soldering of electronic components. The model accounts for grain boundary diffusion between IMC grains and plastic deformation of the microstructure. A plasticity model with hardening, based on an evolving dislocation density, is used for the Cu and Sn phases. Results from the numerical simulations suggest that the thickness of the IMC layer increases linearly with time and that the morphology of the IMC gradually changes from scallop-like to planar, consistent with previous experimental findings. The model predicts that plastic deformation occurs in both the Cu and the Sn layers. Furthermore, the mean value of the biaxial stress in the Sn layer is found to saturate at a level of −8 MPa to −10 MPa during aging. This is in good agreement with experimental data.
Journal of Materials Research and Technology, 2020
Hydrogen peroxide treatment is a cost-effective and simple method to improve the bioactivity of t... more Hydrogen peroxide treatment is a cost-effective and simple method to improve the bioactivity of titanium implants. In this study, the effects of chloride ion concentration and temperature of hydrogen peroxide on the surface treatment of titanium were investigated using X-ray diffractometry (XRD), Field Emission-Scanning Electron Microscopy (FESEM), and tests in order to determine wettability and apatite forming ability. The results showed that at the lower temperatures of treatment (60 • C), hydrogen peroxide corroded the formed titania layer and the post-heat treatment resulted in rutile formation on the surface of titanium. At higher temperatures of treatment (100 • C), a uniform and crack-free anatase layer was formed on the surface of titanium, leading to the improvement of superhydrophilicity and the apatite forming ability of titanium. However, these properties were affected by increasing the chloride concentration of hydrogen peroxide. At appropriate conditions, titanium dental implant surfaces could be treated effectively using hydrogen peroxide, such that the time of treatment could be reduced to 5 h.
The physical properties of polycrystalline materials depend on their microstructure, which is the... more The physical properties of polycrystalline materials depend on their microstructure, which is the nano- to centimeter scale arrangement of phases and defects in their interior. Such microstructure depends on the shape, crystallographic phase and orientation, and interfacing of the grains constituting the material. This article presents a new non-destructive 3D technique to study centimeter-sized bulk samples with a spatial resolution of hundred micrometers: time-of-flight three-dimensional neutron diffraction (ToF 3DND). Compared to existing analogous X-ray diffraction techniques, ToF 3DND enables studies of samples that can be both larger in size and made of heavier elements. Moreover, ToF 3DND facilitates the use of complicated sample environments. The basic ToF 3DND setup, utilizing an imaging detector with high spatial and temporal resolution, can easily be implemented at a time-of-flight neutron beamline. The technique was developed and tested with data collected at the Materia...
A coupled diffusion-deformation, multiphase field model for elastoplastic materials is presented.... more A coupled diffusion-deformation, multiphase field model for elastoplastic materials is presented. The equations governing the evolution of the phase fields and the molar concentration field are derived in a thermodynamically consistent way using microforce balance laws. As an example of its capabilities, the model is used to study the growth of the intermetallic compound (IMC) Cu 6 Sn 5 during room-temperature aging. This IMC is of great importance in, e.g., soldering of electronic components. The model accounts for grain boundary diffusion between IMC grains and plastic deformation of the microstructure. A plasticity model with hardening, based on an evolving dislocation density, is used for the Cu and Sn phases. Results from the numerical simulations suggest that the thickness of the IMC layer increases linearly with time and that the morphology of the IMC gradually changes from scallop-like to planar, consistent with previous experimental findings. The model predicts that plastic deformation occurs in both the Cu and the Sn layers. Furthermore, the mean value of the biaxial stress in the Sn layer is found to saturate at a level of −8 MPa to −10 MPa during aging. This is in good agreement with experimental data.
High temperature thermal stability of nanocrystalline 316L stainless steel processed by highpress... more High temperature thermal stability of nanocrystalline 316L stainless steel processed by highpressure torsion, Materials Science & Engineering A,
We report on two patients with fracture of a modular, tapered and distally fixed, uncemented tita... more We report on two patients with fracture of a modular, tapered and distally fixed, uncemented titanium revision hip stem, not previously described. A failure analysis revealed that the cause of the fractures was the development of fatigue cracks in the mid-stem cobalt-chromium modular junction ending in corrosionfatigue failure. No material defects or stress risers were found in any of the implants. The diameter of the midstem modular junction might be undersized for use in heavy and active patients. We also report a new way of detecting an undisplaced fracture at the modular junction, using the scout image from a computed tomography (CT) scan; a technique that can be used when plain radiographs are inconclusive.
In this work, the surface morphology changes of nanocrystalline Cr 2 O 3 film deposited on Si waf... more In this work, the surface morphology changes of nanocrystalline Cr 2 O 3 film deposited on Si wafer during the heating process were observed in-situ by means of an environmental scanning electron microscope (ESEM). The Cr 2 O 3 film cracked at high temperature due to the cause of thermal stress; the corresponding crack area percentages on the film surface were real-time evaluated using image analysis software (SISC IAS V8.0) based on the principle of gray value analysis. In the meantime, the effects of the heating temperature on the crack area percentage, phase constituents, and grain size of the Cr 2 O 3 film were also studied in detail. The results showed that the percentage of crack area on film surface first increased with the heating temperature rise, and reached the maximum value at around 980 • C, and then gradually declined again. The above trend is closely related to the changes of thermal stress and grain growth in film. In addition, the heat treatment also had a strong influence on the grain size of the Cr 2 O 3 film.
Advances in Powder Metallurgy Particulate Materials 2012 Proceedings of the 2012 International Conference on Powder Metallurgy Particulate Materials Powdermet 2012 June 10 13 Nashville, 2012
The present study focuses on in situ as well as ex situ studies on the sintering of pre-compacted... more The present study focuses on in situ as well as ex situ studies on the sintering of pre-compacted powder mixtures of 50at% Nickel-50at%Titanium. In situ studies were carried out by monitoring the changes in morphology of the fracture surface of the compact continuously during heating in the hot stage of an environmental scanning electron microscope. Results on the initiation of sintering and its variation with the particle size of reactants are presented. Differential Scanning Calorimetry and X-ray diffraction studies have also been made to characterize the formation of intermetallic compounds during the progress of sintering.
The Energy Citations Database (ECD) provides access to historical and current research (1948 to t... more The Energy Citations Database (ECD) provides access to historical and current research (1948 to the present) from the Department of Energy (DOE) and predecessor agencies.
International Journal of Refractory Metals and Hard Materials, 2013
This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/authorsrights
The present study focuses on in situ as well as ex situ studies on the sintering of pre-compacted... more The present study focuses on in situ as well as ex situ studies on the sintering of pre-compacted powder mixtures of 50 at% Nickel-50 at %Titanium. In situ studies were carried out by monitoring the changes in morphology of the fracture surface of the compact continuously during heating in the hot stage of an environmental scanning electron microscope. Results on the initiation of sintering and its variation with the particle size of reactants are presented. Differential Scanning Calorimetry and X-ray diffraction studies have also been made to characterize the formation of intermetallic compounds during the progress of sintering.
Proceedings of the 14th International Workshop on Spallation Materials Technology, Feb 5, 2020
Characterization of thermal and mechanical properties of high-energy proton and spallation neutro... more Characterization of thermal and mechanical properties of high-energy proton and spallation neutron irradiated tungsten was performed. The work includes studies of unirradiated tungsten from various suppliers and processing routes, to determine which grade of tungsten is the most suitable for use as spallation material at the European Spallation Source (ESS). Present fatigue studies on unirradiated tungsten suggest limiting the maximum stress in tungsten to 100 MPa and choosing rolled and annealed material which has proven to be the most durable. Studies of tungsten in mildly oxidising atmospheres, show that even 5 ppm of oxygen impurity in the helium cooling gas is enough to oxidise it. Based on these results, the upper temperature limit in the target during normal operation was set to 500 ˚C. However, both temperature and thermo-mechanical stress in tungsten will alter as the properties of the material change due to irradiation. As available data on irradiated tungsten is very limited, large efforts were made to study tungsten irradiated under similar conditions as the future ESS target material. These studies include irradiation induced changes in thermal diffusivity, hardness, ductility, and ultimate tensile strength. Data from these tests show severe embrittlement of tungsten post-irradiation, with virtually zero plasticity in specimens tested up to 500 °C. Hardness tests showed an increase in hardness by more than 50%, and thermal diffusivity decreased by up to 51%.
We report on two patients with fracture of a modular, tapered and distally fixed, uncemented tita... more We report on two patients with fracture of a modular, tapered and distally fixed, uncemented titanium revision hip stem, not previously described. A failure analysis revealed that the cause of the fractures was the development of fatigue cracks in the mid-stem cobalt-chromium modular junction ending in corrosionfatigue failure. No material defects or stress risers were found in any of the implants. The diameter of the midstem modular junction might be undersized for use in heavy and active patients. We also report a new way of detecting an undisplaced fracture at the modular junction, using the scout image from a computed tomography (CT) scan; a technique that can be used when plain radiographs are inconclusive.
A coupled diffusion-deformation, multiphase field model for elastoplastic materials is presented.... more A coupled diffusion-deformation, multiphase field model for elastoplastic materials is presented. The equations governing the evolution of the phase fields and the molar concentration field are derived in a thermodynamically consistent way using microforce balance laws. As an example of its capabilities, the model is used to study the growth of the intermetallic compound (IMC) Cu 6 Sn 5 during room-temperature aging. This IMC is of great importance in, e.g., soldering of electronic components. The model accounts for grain boundary diffusion between IMC grains and plastic deformation of the microstructure. A plasticity model with hardening, based on an evolving dislocation density, is used for the Cu and Sn phases. Results from the numerical simulations suggest that the thickness of the IMC layer increases linearly with time and that the morphology of the IMC gradually changes from scallop-like to planar, consistent with previous experimental findings. The model predicts that plastic deformation occurs in both the Cu and the Sn layers. Furthermore, the mean value of the biaxial stress in the Sn layer is found to saturate at a level of −8 MPa to −10 MPa during aging. This is in good agreement with experimental data.
Journal of Materials Research and Technology, 2020
Hydrogen peroxide treatment is a cost-effective and simple method to improve the bioactivity of t... more Hydrogen peroxide treatment is a cost-effective and simple method to improve the bioactivity of titanium implants. In this study, the effects of chloride ion concentration and temperature of hydrogen peroxide on the surface treatment of titanium were investigated using X-ray diffractometry (XRD), Field Emission-Scanning Electron Microscopy (FESEM), and tests in order to determine wettability and apatite forming ability. The results showed that at the lower temperatures of treatment (60 • C), hydrogen peroxide corroded the formed titania layer and the post-heat treatment resulted in rutile formation on the surface of titanium. At higher temperatures of treatment (100 • C), a uniform and crack-free anatase layer was formed on the surface of titanium, leading to the improvement of superhydrophilicity and the apatite forming ability of titanium. However, these properties were affected by increasing the chloride concentration of hydrogen peroxide. At appropriate conditions, titanium dental implant surfaces could be treated effectively using hydrogen peroxide, such that the time of treatment could be reduced to 5 h.
The physical properties of polycrystalline materials depend on their microstructure, which is the... more The physical properties of polycrystalline materials depend on their microstructure, which is the nano- to centimeter scale arrangement of phases and defects in their interior. Such microstructure depends on the shape, crystallographic phase and orientation, and interfacing of the grains constituting the material. This article presents a new non-destructive 3D technique to study centimeter-sized bulk samples with a spatial resolution of hundred micrometers: time-of-flight three-dimensional neutron diffraction (ToF 3DND). Compared to existing analogous X-ray diffraction techniques, ToF 3DND enables studies of samples that can be both larger in size and made of heavier elements. Moreover, ToF 3DND facilitates the use of complicated sample environments. The basic ToF 3DND setup, utilizing an imaging detector with high spatial and temporal resolution, can easily be implemented at a time-of-flight neutron beamline. The technique was developed and tested with data collected at the Materia...
A coupled diffusion-deformation, multiphase field model for elastoplastic materials is presented.... more A coupled diffusion-deformation, multiphase field model for elastoplastic materials is presented. The equations governing the evolution of the phase fields and the molar concentration field are derived in a thermodynamically consistent way using microforce balance laws. As an example of its capabilities, the model is used to study the growth of the intermetallic compound (IMC) Cu 6 Sn 5 during room-temperature aging. This IMC is of great importance in, e.g., soldering of electronic components. The model accounts for grain boundary diffusion between IMC grains and plastic deformation of the microstructure. A plasticity model with hardening, based on an evolving dislocation density, is used for the Cu and Sn phases. Results from the numerical simulations suggest that the thickness of the IMC layer increases linearly with time and that the morphology of the IMC gradually changes from scallop-like to planar, consistent with previous experimental findings. The model predicts that plastic deformation occurs in both the Cu and the Sn layers. Furthermore, the mean value of the biaxial stress in the Sn layer is found to saturate at a level of −8 MPa to −10 MPa during aging. This is in good agreement with experimental data.
High temperature thermal stability of nanocrystalline 316L stainless steel processed by highpress... more High temperature thermal stability of nanocrystalline 316L stainless steel processed by highpressure torsion, Materials Science & Engineering A,
We report on two patients with fracture of a modular, tapered and distally fixed, uncemented tita... more We report on two patients with fracture of a modular, tapered and distally fixed, uncemented titanium revision hip stem, not previously described. A failure analysis revealed that the cause of the fractures was the development of fatigue cracks in the mid-stem cobalt-chromium modular junction ending in corrosionfatigue failure. No material defects or stress risers were found in any of the implants. The diameter of the midstem modular junction might be undersized for use in heavy and active patients. We also report a new way of detecting an undisplaced fracture at the modular junction, using the scout image from a computed tomography (CT) scan; a technique that can be used when plain radiographs are inconclusive.
In this work, the surface morphology changes of nanocrystalline Cr 2 O 3 film deposited on Si waf... more In this work, the surface morphology changes of nanocrystalline Cr 2 O 3 film deposited on Si wafer during the heating process were observed in-situ by means of an environmental scanning electron microscope (ESEM). The Cr 2 O 3 film cracked at high temperature due to the cause of thermal stress; the corresponding crack area percentages on the film surface were real-time evaluated using image analysis software (SISC IAS V8.0) based on the principle of gray value analysis. In the meantime, the effects of the heating temperature on the crack area percentage, phase constituents, and grain size of the Cr 2 O 3 film were also studied in detail. The results showed that the percentage of crack area on film surface first increased with the heating temperature rise, and reached the maximum value at around 980 • C, and then gradually declined again. The above trend is closely related to the changes of thermal stress and grain growth in film. In addition, the heat treatment also had a strong influence on the grain size of the Cr 2 O 3 film.
Advances in Powder Metallurgy Particulate Materials 2012 Proceedings of the 2012 International Conference on Powder Metallurgy Particulate Materials Powdermet 2012 June 10 13 Nashville, 2012
The present study focuses on in situ as well as ex situ studies on the sintering of pre-compacted... more The present study focuses on in situ as well as ex situ studies on the sintering of pre-compacted powder mixtures of 50at% Nickel-50at%Titanium. In situ studies were carried out by monitoring the changes in morphology of the fracture surface of the compact continuously during heating in the hot stage of an environmental scanning electron microscope. Results on the initiation of sintering and its variation with the particle size of reactants are presented. Differential Scanning Calorimetry and X-ray diffraction studies have also been made to characterize the formation of intermetallic compounds during the progress of sintering.
The Energy Citations Database (ECD) provides access to historical and current research (1948 to t... more The Energy Citations Database (ECD) provides access to historical and current research (1948 to the present) from the Department of Energy (DOE) and predecessor agencies.
International Journal of Refractory Metals and Hard Materials, 2013
This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/authorsrights
The present study focuses on in situ as well as ex situ studies on the sintering of pre-compacted... more The present study focuses on in situ as well as ex situ studies on the sintering of pre-compacted powder mixtures of 50 at% Nickel-50 at %Titanium. In situ studies were carried out by monitoring the changes in morphology of the fracture surface of the compact continuously during heating in the hot stage of an environmental scanning electron microscope. Results on the initiation of sintering and its variation with the particle size of reactants are presented. Differential Scanning Calorimetry and X-ray diffraction studies have also been made to characterize the formation of intermetallic compounds during the progress of sintering.
Proceedings of the 14th International Workshop on Spallation Materials Technology, Feb 5, 2020
Characterization of thermal and mechanical properties of high-energy proton and spallation neutro... more Characterization of thermal and mechanical properties of high-energy proton and spallation neutron irradiated tungsten was performed. The work includes studies of unirradiated tungsten from various suppliers and processing routes, to determine which grade of tungsten is the most suitable for use as spallation material at the European Spallation Source (ESS). Present fatigue studies on unirradiated tungsten suggest limiting the maximum stress in tungsten to 100 MPa and choosing rolled and annealed material which has proven to be the most durable. Studies of tungsten in mildly oxidising atmospheres, show that even 5 ppm of oxygen impurity in the helium cooling gas is enough to oxidise it. Based on these results, the upper temperature limit in the target during normal operation was set to 500 ˚C. However, both temperature and thermo-mechanical stress in tungsten will alter as the properties of the material change due to irradiation. As available data on irradiated tungsten is very limited, large efforts were made to study tungsten irradiated under similar conditions as the future ESS target material. These studies include irradiation induced changes in thermal diffusivity, hardness, ductility, and ultimate tensile strength. Data from these tests show severe embrittlement of tungsten post-irradiation, with virtually zero plasticity in specimens tested up to 500 °C. Hardness tests showed an increase in hardness by more than 50%, and thermal diffusivity decreased by up to 51%.
We report on two patients with fracture of a modular, tapered and distally fixed, uncemented tita... more We report on two patients with fracture of a modular, tapered and distally fixed, uncemented titanium revision hip stem, not previously described. A failure analysis revealed that the cause of the fractures was the development of fatigue cracks in the mid-stem cobalt-chromium modular junction ending in corrosionfatigue failure. No material defects or stress risers were found in any of the implants. The diameter of the midstem modular junction might be undersized for use in heavy and active patients. We also report a new way of detecting an undisplaced fracture at the modular junction, using the scout image from a computed tomography (CT) scan; a technique that can be used when plain radiographs are inconclusive.
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