Eloisa Alarcon - Academia.edu (original) (raw)
Papers by Eloisa Alarcon
Metallurgical and Materials Transactions A, 2021
The evolution of the crystallographic texture and lattice strain of uranium 6-weight percent niob... more The evolution of the crystallographic texture and lattice strain of uranium 6-weight percent niobium alloy samples are tracked during multiple deformation and heat treating cycles in an effort to understand and control the mechanical properties of the material following thermo-mechanical processing. The heavily twinned microstructure and low-symmetry crystal structure of U-6Nb result in multiple sequential active deformation mechanisms associated with distinctive deformation textures in strain ranges from 0-0.15 true strain. It is found that heating into the high-temperature c-phase erases much of the texture formed during deformation at room temperature in the a¢¢-phase and resets the active deformation mechanisms. Through a small number of deformation/heat treat cycles to moderate strains, i.e.,~0.13 per cycle, the flow strength of the material is recovered to its original value. However, on the fourth such cycle, a reduction of strength is observed and the sample failed.
Department of Earth and Planetary Science, University of California Berkeley, Berkeley, CA 94720,... more Department of Earth and Planetary Science, University of California Berkeley, Berkeley, CA 94720, USA, Department of Physics, New Mexico State University, Las Cruces, NM 88003, USA, Los Alamos Neutron Science Center, Los Alamos National Laboratory, Los Alamos, NM 87545, USA, and Chemical and Earth Sciences Department, The University of Modena and Reggio Emilia, Via S. Eufemia 19, I-41121, Modena, Italy. Correspondence e-mail: wenk@berkeley.edu
Author(s): Zepeda-Alarcon, Eloisa | Advisor(s): Wenk, Hans-Rudolf | Abstract: The vast majority o... more Author(s): Zepeda-Alarcon, Eloisa | Advisor(s): Wenk, Hans-Rudolf | Abstract: The vast majority of rocks that constitute the Earth are composed of multiple mineral phases and complicated deformation conditions are found everywhere, yet little is known about plastic deformation of polyphase polycrystalline rocks, especially with low symmetry phases and highly contrasting mechanical properties. In particular, plastic deformation of mantle rocks is of interest for its connection to geophysical processes, such as mantle convection, slab subduction and upwelling plumes. Seismic observations show regions in the mantle where seismic waves encounter large scale anisotropy of the rocks they propagate in. Although there are many possible reasons for this large scale anisotropic signature of these particular regions, in the upper mantle it has been connected to the development of crystallographic preferred orientation, hereafter called texture, of the mineral olivine due to plastic deformation...
Metallurgical and Materials Transactions A, 2021
The microstructure of additively manufactured Ti-6Al-4V (Ti64) produced by a laser powder bed fus... more The microstructure of additively manufactured Ti-6Al-4V (Ti64) produced by a laser powder bed fusion process was studied during post-build heat treatments between 1043 K (770 °C) and just above the β transus temperature 1241 K (1008 °C) in situ using high-energy X-ray diffraction. Parallel studies on traditionally manufactured wrought and annealed Ti64 were completed as a baseline comparison. The initial and final grain structures were characterized using electron backscatter diffraction. Likewise, the initial texture, dislocation density, and final texture were determined with X-ray diffraction. The evolution of the microstructure, including the phase evolution, internal stress, qualitative dislocation density, and vanadium distribution between the constituent phases were monitored with in situ X-ray diffraction. The as-built powder bed fusion material was single-phase hexagonal close packed (to the measurement resolution) with a fine acicular grain structure and exhibited a high dislocation density and intergranular residual stress. Recovery of the high dislocation density and annealing of the internal stress were observed to initiate concurrently at a relatively low temperature of 770 K (497 °C). Transformation to the β phase initiated at roughly 913 K (640 °C), after recovery had occurred. These results are meant to be used to design post-build heat treatments resulting in specified microstructures and properties.
Acta Materialia, 2020
A bridgmanite/periclase aggregate is investigated due to its prevalence in the Earth's lower mant... more A bridgmanite/periclase aggregate is investigated due to its prevalence in the Earth's lower mantle and its importance for understanding geodynamic processes. In dual-phase polycrystalline aggregates, both strength contrast between phases and single crystal elastic and plastic anisotropy are known to influence the development of intragrain misorientation, and the evolution of crystallographic texture. In this study, full-field crystal plasticity simulations are performed with a finite element solution method, and applied to an aggregate of a mechanically strong orthorhombic phase with perovskite structure (bridgmanite, MgSiO 3), and a relatively weaker cubic phase (periclase, MgO). The relative strengths of the phases are parameterized to elucidate the effect that strength contrast has on texture evolution and single-phase simulations are performed for comparison. Overall, results indicate that the relative strength between the two phases influences the development of plasticity, and the overall texture evolution. Results are discussed in light of trends related to the evolution of plasticity and misorientation in the aggregate, and their dependence on both the strength contrast between phases as well as the spatial distribution of grains and phases.
The Proceedings of the Materials and Mechanics Conference, 2014
Earth and Planetary Science Letters, 2016
The lower mantle is estimated to be composed of mostly bridgmanite and a smaller percentage of fe... more The lower mantle is estimated to be composed of mostly bridgmanite and a smaller percentage of ferropericlase, yet very little information exists for two-phase deformation of these minerals. To better understand the rheology and active deformation mechanisms of these lower mantle minerals, especially dislocation slip and the development of crystallographic preferred orientation (CPO), we deformed mineral analogs neighborite (NaMgF 3 , iso-structural with bridgmanite) and halite (NaCl, isostructural with ferropericlase) together in the deformation-DIA at the Advanced Photon Source up to 51% axial shortening. Development of CPO was recorded in situ with X-ray diffraction, and information on microstructural evolution was collected using X-ray microtomography. Results show that when present in as little as 15% volume, the weak phase (NaCl) controls the deformation. Compared to single phase NaMgF 3 samples, samples with just 15% volume NaCl show a reduction of CPO in NaMgF 3 and weakening of the aggregate. Microtomography shows both NaMgF 3 and NaCl form highly interconnected networks of grains. Polycrystal plasticity simulations were carried out to gain insight into slip activity, CPO evolution, and strain and stress partitioning between phases for different synthetic two-phase microstructures. The results suggest that ferropericlase may control deformation in the lower mantle and reduce CPO in bridgmanite, which implies a less viscous lower mantle and helps to explain why the lower mantle is fairly isotropic.
Geophysical Research Letters, 2016
Lattice distortions in crystals can be mapped at the micron scale using synchrotron X-ray Laue mi... more Lattice distortions in crystals can be mapped at the micron scale using synchrotron X-ray Laue microdiffraction (μXRD). From lattice distortions the shape and orientation of the elastic strain tensor can be derived and interpreted in terms of residual stress. Here we apply the new method to vein quartz from the original boudinage locality at Bastogne, Belgium. A long-standing debate surrounds the kinematics of the Bastogne boudins. The μXRD measurements reveal a shortening residual elastic strain, perpendicular to the vein wall, corroborating the model that the Bastogne boudins formed by layer-parallel shortening and not by layer-parallel extension, as is in the geological community generally inferred by the process of boudinage.
Journal of Applied Crystallography, 2014
The magnetic structure of two natural samples of goethite (α-FeOOH) with varying crystallinity wa... more The magnetic structure of two natural samples of goethite (α-FeOOH) with varying crystallinity was analyzed at 15 and 300 K by neutron diffraction. The well crystallized sample has thePb′nmcolor space group and remained antiferromagnetic up to 300 K, with spins aligned parallel to thecaxis. The purely magnetic 100 peak, identifying this color space group, was clearly resolved. The nanocrystalline sample shows a phase transition to the paramagnetic state at a temperature below 300 K. This lowering of the Néel temperature may be explained by the interaction of magnetic clusters within particles. The nuclear structure, refined with the Rietveld and pair distribution function methods, is consistent with reports in the literature.
Review of Scientific Instruments, 2013
To extend the range of high-temperature, high-pressure studies within the diamond anvil cell, a L... more To extend the range of high-temperature, high-pressure studies within the diamond anvil cell, a Liermann-type diamond anvil cell with radial diffraction geometry (rDAC) was redesigned and developed for synchrotron X-ray diffraction experiments at beamline 12.2.2 of the Advanced Light Source. The rDAC, equipped with graphite heating arrays, allows simultaneous resistive and laser heating while the material is subjected to high pressure. The goals are both to extend the temperature range of external (resistive) heating and to produce environments with lower temperature gradients in a simultaneously resistive-and laser-heated rDAC. Three different geomaterials were used as pilot samples to calibrate and optimize conditions for combined resistive and laser heating. For example, in Run#1, FeO was loaded in a boron-mica gasket and compressed to 11 GPa then gradually resistively heated to 1007 K (1073 K at the diamond side). The laser heating was further applied to FeO to raise temperature to 2273 K. In Run#2, Fe-Ni alloy was compressed to 18 GPa and resistively heated to 1785 K (1973 K at the diamond side). The combined resistive and laser heating was successfully performed again on (Mg 0.9 Fe 0.1)O in Run#3. In this instance, the sample was loaded in a boron-kapton gasket, compressed to 29 GPa, resistive-heated up to 1007 K (1073 K at the diamond side), and further simultaneously laser-heated to achieve a temperature in excess of 2273 K at the sample position. Diffraction patterns obtained from the experiments were deconvoluted using the Rietveld method and quantified for lattice preferred orientation of each material under extreme conditions and during phase transformation.
Review of Scientific Instruments, 2013
Metallurgical and Materials Transactions A, 2021
The evolution of the crystallographic texture and lattice strain of uranium 6-weight percent niob... more The evolution of the crystallographic texture and lattice strain of uranium 6-weight percent niobium alloy samples are tracked during multiple deformation and heat treating cycles in an effort to understand and control the mechanical properties of the material following thermo-mechanical processing. The heavily twinned microstructure and low-symmetry crystal structure of U-6Nb result in multiple sequential active deformation mechanisms associated with distinctive deformation textures in strain ranges from 0-0.15 true strain. It is found that heating into the high-temperature c-phase erases much of the texture formed during deformation at room temperature in the a¢¢-phase and resets the active deformation mechanisms. Through a small number of deformation/heat treat cycles to moderate strains, i.e.,~0.13 per cycle, the flow strength of the material is recovered to its original value. However, on the fourth such cycle, a reduction of strength is observed and the sample failed.
Department of Earth and Planetary Science, University of California Berkeley, Berkeley, CA 94720,... more Department of Earth and Planetary Science, University of California Berkeley, Berkeley, CA 94720, USA, Department of Physics, New Mexico State University, Las Cruces, NM 88003, USA, Los Alamos Neutron Science Center, Los Alamos National Laboratory, Los Alamos, NM 87545, USA, and Chemical and Earth Sciences Department, The University of Modena and Reggio Emilia, Via S. Eufemia 19, I-41121, Modena, Italy. Correspondence e-mail: wenk@berkeley.edu
Author(s): Zepeda-Alarcon, Eloisa | Advisor(s): Wenk, Hans-Rudolf | Abstract: The vast majority o... more Author(s): Zepeda-Alarcon, Eloisa | Advisor(s): Wenk, Hans-Rudolf | Abstract: The vast majority of rocks that constitute the Earth are composed of multiple mineral phases and complicated deformation conditions are found everywhere, yet little is known about plastic deformation of polyphase polycrystalline rocks, especially with low symmetry phases and highly contrasting mechanical properties. In particular, plastic deformation of mantle rocks is of interest for its connection to geophysical processes, such as mantle convection, slab subduction and upwelling plumes. Seismic observations show regions in the mantle where seismic waves encounter large scale anisotropy of the rocks they propagate in. Although there are many possible reasons for this large scale anisotropic signature of these particular regions, in the upper mantle it has been connected to the development of crystallographic preferred orientation, hereafter called texture, of the mineral olivine due to plastic deformation...
Metallurgical and Materials Transactions A, 2021
The microstructure of additively manufactured Ti-6Al-4V (Ti64) produced by a laser powder bed fus... more The microstructure of additively manufactured Ti-6Al-4V (Ti64) produced by a laser powder bed fusion process was studied during post-build heat treatments between 1043 K (770 °C) and just above the β transus temperature 1241 K (1008 °C) in situ using high-energy X-ray diffraction. Parallel studies on traditionally manufactured wrought and annealed Ti64 were completed as a baseline comparison. The initial and final grain structures were characterized using electron backscatter diffraction. Likewise, the initial texture, dislocation density, and final texture were determined with X-ray diffraction. The evolution of the microstructure, including the phase evolution, internal stress, qualitative dislocation density, and vanadium distribution between the constituent phases were monitored with in situ X-ray diffraction. The as-built powder bed fusion material was single-phase hexagonal close packed (to the measurement resolution) with a fine acicular grain structure and exhibited a high dislocation density and intergranular residual stress. Recovery of the high dislocation density and annealing of the internal stress were observed to initiate concurrently at a relatively low temperature of 770 K (497 °C). Transformation to the β phase initiated at roughly 913 K (640 °C), after recovery had occurred. These results are meant to be used to design post-build heat treatments resulting in specified microstructures and properties.
Acta Materialia, 2020
A bridgmanite/periclase aggregate is investigated due to its prevalence in the Earth's lower mant... more A bridgmanite/periclase aggregate is investigated due to its prevalence in the Earth's lower mantle and its importance for understanding geodynamic processes. In dual-phase polycrystalline aggregates, both strength contrast between phases and single crystal elastic and plastic anisotropy are known to influence the development of intragrain misorientation, and the evolution of crystallographic texture. In this study, full-field crystal plasticity simulations are performed with a finite element solution method, and applied to an aggregate of a mechanically strong orthorhombic phase with perovskite structure (bridgmanite, MgSiO 3), and a relatively weaker cubic phase (periclase, MgO). The relative strengths of the phases are parameterized to elucidate the effect that strength contrast has on texture evolution and single-phase simulations are performed for comparison. Overall, results indicate that the relative strength between the two phases influences the development of plasticity, and the overall texture evolution. Results are discussed in light of trends related to the evolution of plasticity and misorientation in the aggregate, and their dependence on both the strength contrast between phases as well as the spatial distribution of grains and phases.
The Proceedings of the Materials and Mechanics Conference, 2014
Earth and Planetary Science Letters, 2016
The lower mantle is estimated to be composed of mostly bridgmanite and a smaller percentage of fe... more The lower mantle is estimated to be composed of mostly bridgmanite and a smaller percentage of ferropericlase, yet very little information exists for two-phase deformation of these minerals. To better understand the rheology and active deformation mechanisms of these lower mantle minerals, especially dislocation slip and the development of crystallographic preferred orientation (CPO), we deformed mineral analogs neighborite (NaMgF 3 , iso-structural with bridgmanite) and halite (NaCl, isostructural with ferropericlase) together in the deformation-DIA at the Advanced Photon Source up to 51% axial shortening. Development of CPO was recorded in situ with X-ray diffraction, and information on microstructural evolution was collected using X-ray microtomography. Results show that when present in as little as 15% volume, the weak phase (NaCl) controls the deformation. Compared to single phase NaMgF 3 samples, samples with just 15% volume NaCl show a reduction of CPO in NaMgF 3 and weakening of the aggregate. Microtomography shows both NaMgF 3 and NaCl form highly interconnected networks of grains. Polycrystal plasticity simulations were carried out to gain insight into slip activity, CPO evolution, and strain and stress partitioning between phases for different synthetic two-phase microstructures. The results suggest that ferropericlase may control deformation in the lower mantle and reduce CPO in bridgmanite, which implies a less viscous lower mantle and helps to explain why the lower mantle is fairly isotropic.
Geophysical Research Letters, 2016
Lattice distortions in crystals can be mapped at the micron scale using synchrotron X-ray Laue mi... more Lattice distortions in crystals can be mapped at the micron scale using synchrotron X-ray Laue microdiffraction (μXRD). From lattice distortions the shape and orientation of the elastic strain tensor can be derived and interpreted in terms of residual stress. Here we apply the new method to vein quartz from the original boudinage locality at Bastogne, Belgium. A long-standing debate surrounds the kinematics of the Bastogne boudins. The μXRD measurements reveal a shortening residual elastic strain, perpendicular to the vein wall, corroborating the model that the Bastogne boudins formed by layer-parallel shortening and not by layer-parallel extension, as is in the geological community generally inferred by the process of boudinage.
Journal of Applied Crystallography, 2014
The magnetic structure of two natural samples of goethite (α-FeOOH) with varying crystallinity wa... more The magnetic structure of two natural samples of goethite (α-FeOOH) with varying crystallinity was analyzed at 15 and 300 K by neutron diffraction. The well crystallized sample has thePb′nmcolor space group and remained antiferromagnetic up to 300 K, with spins aligned parallel to thecaxis. The purely magnetic 100 peak, identifying this color space group, was clearly resolved. The nanocrystalline sample shows a phase transition to the paramagnetic state at a temperature below 300 K. This lowering of the Néel temperature may be explained by the interaction of magnetic clusters within particles. The nuclear structure, refined with the Rietveld and pair distribution function methods, is consistent with reports in the literature.
Review of Scientific Instruments, 2013
To extend the range of high-temperature, high-pressure studies within the diamond anvil cell, a L... more To extend the range of high-temperature, high-pressure studies within the diamond anvil cell, a Liermann-type diamond anvil cell with radial diffraction geometry (rDAC) was redesigned and developed for synchrotron X-ray diffraction experiments at beamline 12.2.2 of the Advanced Light Source. The rDAC, equipped with graphite heating arrays, allows simultaneous resistive and laser heating while the material is subjected to high pressure. The goals are both to extend the temperature range of external (resistive) heating and to produce environments with lower temperature gradients in a simultaneously resistive-and laser-heated rDAC. Three different geomaterials were used as pilot samples to calibrate and optimize conditions for combined resistive and laser heating. For example, in Run#1, FeO was loaded in a boron-mica gasket and compressed to 11 GPa then gradually resistively heated to 1007 K (1073 K at the diamond side). The laser heating was further applied to FeO to raise temperature to 2273 K. In Run#2, Fe-Ni alloy was compressed to 18 GPa and resistively heated to 1785 K (1973 K at the diamond side). The combined resistive and laser heating was successfully performed again on (Mg 0.9 Fe 0.1)O in Run#3. In this instance, the sample was loaded in a boron-kapton gasket, compressed to 29 GPa, resistive-heated up to 1007 K (1073 K at the diamond side), and further simultaneously laser-heated to achieve a temperature in excess of 2273 K at the sample position. Diffraction patterns obtained from the experiments were deconvoluted using the Rietveld method and quantified for lattice preferred orientation of each material under extreme conditions and during phase transformation.
Review of Scientific Instruments, 2013