Change In Crystallographic Orientation Research Articles

Microtexture region segmentation of eddy current testing data using a structural prior

Microtexture regions (MTRs) are collections of grains with similar crystallographic orientation. Because their presence in titanium alloys can significantly impact aerospace component life, a nondestructive method to detect and characterize MTR is needed. In this work, we propose to use data from two nondestructive evaluation methods, eddy current testing (ECT) and scanning acoustic microscopy (SAM), in order to recover the boundary and dominant crystallographic orientation of each MTR in a specimen. ECT is an electromagnetic method that is sensitive to changes in crystallographic orientation associated with MTR; however, its low resolution prevents it from resolving MTR boundaries well. In contrast, SAM is a high frequency ultrasound method that is able to resolve MTR boundaries but is not sensitive to orientation. This paper proposes an algorithm to characterize MTR that makes use of a method known as covariance generalized matching component analysis. This method is used to build a surrogate linear forward model that relates MTR boundaries and orientation to ECT data. The model is inverted using the SAM data as a structural prior. We demonstrate this technique using simulated ECT and experimental SAM data from a large grain titanium specimen.

Strengthening effect in laser metal deposited Ti6Al4V alloy via layer-by-layer ultrasonic impact treatment

The present work investigates the influence of incorporation of the layer-by-layer ultrasonic impact treatment (UIT) into the laser metal deposition (LMD) processing of Ti6Al4V alloy. The microstructure and mechanical properties of the samples with/without the assistance of UIT are comparatively studied. The curved shape boundaries of α/α′ phase with inconsistent misorientation angles and the ultra-fine α phase are observed in the UIT-assisted LMD (ULMD) sample. The α/α′ phase in the ULMD sample is characterized by high-density dislocations, larger lattice strain and distortion in comparison with that in the LMD sample. An ultimate tensile strength of 1386 MPa is obtained in the ULMD sample that exceeds that of the LMD sample by 373 MPa and is superior to the values reported in majority of the previous works. Crystallographic orientation change, increased dislocation density and α/α′ phase lattice distortion, and formation of ultra-fine α grains are found to influence the properties. The present work provides an in-depth understanding of the mechanisms/factors influencing the mechanical strengths of additive-manufactured titanium alloys.

Factors governing surface exchange kinetics in undoped and strontium/iron co-substituted La2NiO4+δ

Surface oxygen exchange in the La2NiO4+δ and La1.5Sr0.5Ni1-yFeyO4+δ (y = 0.3, 0.4) oxides is analyzed using the data on oxygen permeability through the membranes with different thicknesses measured under various oxygen partial pressure P(O2) gradients in the 800–1000 °C range. The increase in P(O2) gradient induced surface limitations in La2NiO4+δ leading to a predominant role of surface exchange in the overall oxygen flux. The origin of surface exchange limitations in La2NiO4+δ is ascribed to a relatively fast decrease in oxygen excess and Ni3+ concentration with P(O2) reduction compared to La1.5Sr0.5Ni0.7Fe0.3O4+δ and La1.5Sr0.5Ni0.6Fe0.4O4+δ, which retained an oxygen excess. Faster surface exchange kinetics for La1.5Sr0.5Ni0.6Fe0.4O4+δ in comparison with that for La1.5Sr0.5Ni0.7Fe0.3O4+δ is interpreted on the basis of surface microstructure obtained by electron backscatter diffraction (EBSD). It is suggested that the observed changes in size, shape and crystallographic orientation of grains in La1.5Sr0.5Ni0.6Fe0.4O4+δ (compared to La1.5Sr0.5Ni0.7Fe0.3O4+δ) could result in a higher amount of 3d-metal cations in surface layers of the oxide.

In-situ investigation on tensile properties of a novel Ti/Al composite sheet

• The discrepancy of mechanical properties between ti and al layers evidences the slip bands with 45° to tensile direction in Al grains. • Morphology and/or crystallographic orientation changes in al grains of composite achieve a compatible deformation. • Heterogeneous deformation induced stress concentration facilitates the initiation of micro-crack and sequential failure at the interfacial zone. Laminated/bimetal composites can offer the advantage of combining constituent metals, but their heterogeneous microstructures exhibit different mechanical properties during subsequent remanufacturing process than those of the homogeneous counterparts. This study investigated the tensile properties, microstructural evolution and deformation behaviours of a new explosive welded TA1/5083 composite sheet using the in-situ characterisation. It is found that a wavy transition zone forms in the composite sheet, showing gradients in the element diffusion and micro-hardness adjacent to the interface. The slip bands with the tensile direction of 45 ° primarily occur in the 5083 side (rather than the TA1 side) with an increase in deformation. Although the dislocation density of the grains in the 5083 layer increases significantly, these grains are slightly elongated along the tensile direction without a significant orientation change. Three deformation stages and a subsequent crack initiation stage appear during the in-situ tensile process. The initiation of micro-cracks in the interfacial zone results from the internal stress concentration occurring at the bottom of interfacial wave structure. Once initial micro-cracks evolve into the intermetallic compounds (IMCs) of the interfacial zone, the high magnitude of stress concentrations of the TA1 and 5083 layers leads to necking and sequential fractures. This study can provide a reference for the design of high-quality Ti/Al composite components for industry.

Microstructural analysis and electro-optic properties of thick epitaxial BaTiO3 films integrated on silicon (001)

Recent advances in epitaxial oxide deposition have enabled the fabrication of thick films of ferroelectric perovskite ${\mathrm{BaTiO}}_{3}$ capable of providing a robust electro-optic response via the Pockels effect in silicon photonic devices. We report a microstructure analysis of such films integrated on Si(001) by molecular beam epitaxy, showing how the crystallographic and polarization orientation change as a function of thickness. The measured electro-optic properties of the film correlate well with the microstructural analysis and demonstrate the potential of Si-integrated ${\mathrm{BaTiO}}_{3}$ for silicon photonics. An effective Pockels coefficient of up to 268 pm/V has been demonstrated in 110-nm-thick films in transmission measurements and 352 pm/V in waveguide measurements.

Effect of dislocation pattern on the magnetic domain structure of pure polycrystalline Ni

We investigated the influence of discrete dislocation, dislocation cell, and cell block on the magnetic domain structure in deformed polycrystalline Ni. Discrete dislocation and dislocation cell structure manifested a short-range effect on the local domain structure. By contrast, dislocation cell block structure significantly changed the magnetic domain by generating 180° domain walls. Our observations indicated that the change of magnetic property as a function of plastic deformation should be discontinuous. However, in macroscale, the coercivity and hysteresis loss monotonically increased as increasing flow stress increases. The discrepancy between the phenomena at different scales is attributed to the crystallographic orientation change in plastic deformation.

Synthesis of LTA zeolite membranes from metal alkoxides and examination of the pervaporation performance

In the dehydration of ethanol, membrane separation using LTA zeolites is commonly employed in place of distillation due to its lower energy consumption. In the membrane separation process, a thin zeolite membrane is preferred to reduce the permeation resistance of water in the membrane. From the aspect of reducing the resistance, the authors successfully prepared LTA zeolite membranes from metal alkoxides. The influence of the crystal growth conditions on the separation performance was investigated by the pervaporation of an ethanol-water mixture. As a result, the thickness of the LTA zeolite membrane could be decreased to less than 3 μm by optimizing the aging time of the secondary growth solution and secondary growth time. For 90 wt% ethanol solution at 343 K, the permeation flux and separation factor of the membrane were 6.3 kg m −2 h −1 and >10,000, respectively. In this paper, the SEM observation and XRD analysis were examined to understand the structure of zeolite membrane. As a result, the change in crystallographic orientation caused by the aging was proposed as key factor of permeability of the membrane. • LTA zeolite membrane was prepared by hydrothermal treatment of seed crystals with hydrolyzed metal alkoxide. • Influence of aging of secondary growth solution of the membrane on its pervaporation performance was examined. • Water permeability of the membrane decreased as the aging proceeded. • X-ray diffraction analysis of the membrane surface revealed that orientation of the crystallites in the LTA layer changed to less (200) plane being parallel to the surface of the membrane. • Decrease of (200) oriented plane by the aging may be responsible for the reduction of water permeability of the membrane.

Utilizing Iron as Reinforcement to Enhance Ambient Mechanical Response and Impression Creep Response of Magnesium

To realize light-weight materials with high strength and ductility, an effective route is to incorporate strong and stiff metallic elements in light-weight matrices. Based on this approach, in this work, magnesium–iron (Mg-Fe) composites were designed and characterized for their microstructure and mechanical properties. The Mg-Fe binary system has extremely low solubility of Fe in the Mg-rich region. Pure magnesium was incorporated with 5, 10, and 15 wt.% Fe particles to form Mg-Fe metal–metal composites by the disintegrated melt deposition technique, followed by hot extrusion. Results showed that the iron content influences (i) the distribution of Fe particles in the Mg matrix, (ii) grain refinement, and (iii) change in crystallographic orientation. Mechanical testing showed that amongst the composites, Mg-5Fe had the highest hardness, strength, and ductility due to (a) the uniform distribution of Fe particles in the Mg matrix, (b) grain refinement, (c) texture randomization, (d) Fe particles acting as effective reinforcement, and (e) absence of deleterious interfacial reactions. Under impression creep, the Mg-5Fe composite had a creep rate similar to those of commercial creep-resistant AE42 alloys and Mg ceramic composites at 473 K. Factors influencing the performance of Mg-5Fe and other Mg metal–metal composites having molybdenum, niobium, and titanium (elements with low solubility in Mg) are presented and discussed.

Physical Properties of Different Thicknesses ZnO Thin Films Prepared via Sol-gel Spin Coating Technique

This paper presents the investigation of the thickness of the ZnO thin films by varying the number of deposition layers during the spin coating deposition process. ZnO thin films were deposited with a different number of layers (ranging from 1, 3, and 5), and the main purpose of this study is to explore the effect of the thickness on the properties of ZnO thin films. The deposited thin films were characterised using field emission scanning electron microscope, surface profilometer, and X-ray diffraction. From the characterisation results, the morphology of the ZnO thin films changed significantly with the number of layers and their thickness value. As expected, the thickness increased as the number of layers increased. The crystalline quality of the deposited film improved as the thickness increased. A change in crystallographic orientation was also observed in which the thicker, thin films showed crystal growth in the (102) direction, whereas the thinner one was in the (101) direction. A slight increase in crystallite size for dominant orientation also was observed with the increase of film thickness.

Deformation-induced Japan twinning in quartz during incipient mylonitization

Abstract Many crystalline rocks of the continental crust contain coarse-grained quartz as a main mineral (e.g., granitoids). Incipient deformation of coarse quartz, which likely controls the accumulation of bulk strain in heterogeneously deformed crustal rock volumes, commonly develops microshear zones (MSZs) of localized recrystallization. At mid-crustal conditions, where quartz deformation is mostly accomplished by subgrain rotation recrystallization, grains of MSZs can show an abrupt change in crystallographic orientation (large misorientation angle) with respect to the host quartz that is still not fully understood. We analyzed MSZs (20–200 µm thick) from deformed coarse-grained (millimeter grain size) quartz veins in the Austroalpine Schobergruppe (Eastern Alps). Electron backscatter diffraction analysis reveals that the MSZs are characterized by a nearly 90° misorientation angle between the c-axes of the host and new grains, which also share one {m} and one {1122} pole, compatible with Japan twinning. This abrupt switch of the c-axis orientation can promote geometrical softening and shear localization. So far, Japan twinning has been interpreted as a growth feature. We show that deformation-induced twinning in quartz, including Japan and Dauphiné twinning, can play an important role in initiation of crystal-plastic deformation within the crust.

Uniform Zn Deposition Achieved by Conductive Carbon Additive for Zn Anode in Zinc‐Ion Hybrid Supercapacitors

The nonuniform zinc nucleation process on the surface of zinc metal anodes is known to result in irreversible dendrite growth, which brings the risk of short circuit for the zinc‐ion hybrid supercapacitor (ZIHS). Herein, a conductive carbon−zinc composite anode with dense active sites is reported to achieve controllable dendrite growth. This unique modified anode in the ZIHS enables extremely low polarization (47 mV) in the symmetric battery test and delivers excellent application performance (capacity retention of 97.7% for 10 000 cycles). In addition, the changes in crystallographic orientation and morphological characteristics of the zinc electrode during deposition are observed by ex situ analysis. The improved zinc nucleation pattern of the modified anode verifies that the carbon additive can significantly facilitate isotropy in Zn deposition. Such a successful application of this economic and expandable modification strategy shows that carbon additives have significant potential in improving the stability of the anode.

Impact of helium irradiation on the crystallographic orientation change in single-crystalline tungsten * *This manuscript has been authored in part by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish

Understanding the helium effects on the surface modifications of tungsten is of great interest and significance for developing plasma-facing materials. Our recent studies revealed that the ion irradiation of helium at room temperature produces 〈111〉-oriented surface grains in single-crystalline tungsten {100} and {110}, which may play an important role in the surface and subsurface evolutions of tungsten subjected to fusion-relevant service environments. Although the driving force for the formation of surface grains is well explained by ion channeling effect, the underlying formation mechanism remains unclear. In this work, we investigated the orientation relationship between irradiation-induced new surface grains and single-crystalline tungsten matrix. The experimental results of electron backscatter diffraction demonstrated that the formation of most 〈111〉-oriented surface grains in both helium-irradiated tungsten {100} or {110} can be regarded as the grain rotation of matrix around its in-plane 〈110〉 axis.

Estimation of microtexture region orientation distribution functions using eddy current data

Microtexture regions (MTRs) within titanium alloys are collections of grains with similar crystallographic orientation. The presence of MTRs can be detrimental to the life of an engine component; as such, a method to detect and characterize MTRs is needed. One potential technique to characterize MTRs is eddy current (EC) testing, which is a nondestructive evaluation technique that is sensitive to the changes in local conductivity due to changes in local crystallographic orientation. While it has been established in the literature that EC methods are sensitive to the presence of MTRs, work has begun only recently to determine the ability of EC to characterize MTRs. In this work, we develop an algorithm to estimate the orientation distribution function of an MTR of interest using EC data. The method relies on an application of the central limit theorem, and the inverse problem is solved in using a likelihood-free technique. Numerical examples using simulated EC data are shown.

Kyanite preserves prograde and retrograde metamorphic events as revealed by cathodoluminescence, geochemistry, and crystallographic orientation

AbstractCathodoluminescence (CL) images of kyanite reveal several internal textures, including sector zoning, oscillatory zoning, and cross‐cutting relationships among different domains. Many textures observed in kyanite correspond to discrete events, thereby connecting kyanite textures to the pressure–temperature (P–T) history of the rock. To evaluate the record of metamorphism preserved by kyanite, metapelites were selected from three different orogens that reflect P–T conditions ranging from amphibolite to ultrahigh‐pressure (UHP) facies. Cross‐correlation of variations in CL intensity, chemistry, and crystal orientation within kyanite indicate the following findings. First, the preservation of original growth zones in kyanite from poly‐metamorphic rocks demonstrates that growth zoning in kyanite persists through metamorphic events and is not erased by diffusion or complete recrystallization. In some samples, kyanite retains evidence of its reaction history during growth. Second, measured changes in absolute crystallographic orientation do not correspond with changes in CL intensity in any of the measured samples, including kyanite twins. Third, both kink banding and undulatory extinction are present across all samples, consistent with rotation about <010> in the (100)[001] slip system. Kyanite from (U)HP samples exhibits higher amplitude undulations than kyanite from lower‐grade lithologies, suggesting that crystallographic orientation data may provide complementary insight about deformation along the P–T path. Fourth, specific CL and trace element signatures in kyanite can be correlated with discrete metamorphic histories; yet, CL intensity and colour are affected by multiple elements, not a single controlling element. In sum, multiple generations of kyanite can be identified by careful cross‐correlation of CL and geochemical data, and when combined with crystal orientation data, kyanite provides a robust record of a rock's P–T evolution.

Microstructure of zirconium fuel claddings: TEM and EBSD studies of as-received and ne-utron-irradiated materials

Zirconium fuel claddings act as a first barrier against release of fission products during nuclear power plant operation and interim storage of the spent fuel. During the reactor operation, cladding tubes are exposed to different stress level at elevated temperatures and neutron irradiation in corrosive environment. It causes a material degradation by corrosion, cladding embrittlement by hydrides and radiation-induced damage or radi-ation growth and creep of the fuel rods. The irradiation damage effects mainly contribute to the loss of material ductility. In our study, microstructure of as-received (non-irradiated) Zr-alloys used in LWR (Zr1Nb, Zr-1Nb-1.2Sn-0.1Fe, Zr-1.5Sn-0.2Fe-0.1Cr) were examined by electron microscopy methods. Transmission electron microscope (TEM) was used to describe the microstructure of claddings used in different reactor conditions and identify the radiation-induced damage, which is presented on Zr1Nb irradiated to one standard campaign in the VVER-1000 active zone. Following Electron Backscatter Diffraction (EBSD) method on transparent foils complements the TEM results in larger area, i. e. by grain size and orientation or analysis of local misorienta-tion after irradiation. Radiation-induced damage was observed in Zr1Nb metallic matrix as type disloca-tion loops, presence of radiation-induced precipitates or partial amorphization of the secondary phase particles. EBSD method showed no changes in crystallographic orientation, but a local increase of dislocation density can be affected by neutron irradiation.

Microstructures and Fabric Transitions of Natural Ice from the Styx Glacier, Northern Victoria Land, Antarctica

We investigated the microstructures of five ice core samples from the Styx Glacier, northern Victoria Land, Antarctica. Evidence of dynamic recrystallization was found in all samples: those at 50 m mainly by polygonization, and those at 170 m, largely by grain boundary migration. Crystallographic preferred orientations of all analyzed samples (view from the surface) typically showed a single cluster of c-axes normal to the surface. A girdle intersecting the single cluster occurs at 140–170 m with a tight cluster of a-axes normal to the girdle. We interpret the change of crystallographic preferred orientations (CPOs) at <140 m as relating to a combination of vertical compression, and shear on a horizontal plane, and the girdle CPOs at depths >140 m, as the result of horizontal extension. Based on the data obtained from the ground penetrating radar, the underlying bedrock topography of a nunatak could have generated the extensional stress regime in the study area. The results imply changeable stress regimes that may occur during burial as a result of external kinematic controls, such as an appearance of a small peak in the bedrock.

Hydration of a Mantle Shear Zone Beyond Serpentine Stability: A Possible Link to Microseismicity Along Ultraslow Spreading Ridges?

AbstractHydration of the oceanic mantle is a fundamental process of the global water cycle promoting chemical and volumetric changes and facilitating mantle exhumation along detachment faults. At which depth these processes occur and how fluids circulate along ductile mantle shear zones are, however, less well constrained. Here we present field, chemical, and microstructural evidence of hydration processes of peridotite mylonites within an upper mantle shear zone from an Alpine ophiolite (Lanzo massif, Italy). Mylonitic and ultramylonitic areas of the anastomosing shear zone are enriched in Cl‐bearing amphibole. Electron backscatter diffraction (EBSD) data indicate the activation of the (100)[001] amphibole slip system arguing for synkinematic growth and deformation at temperatures consistent with Mg‐hornblende stability between 800°C and 850°C. High Cl contents in amphibole (0.15–0.61 wt%) as well as oxygen isotope data (δ18Owhole‐rock between 4.4‰ and 4.7‰) indicate accumulation and focusing of seawater‐derived fluid in mylonitic and ultramylonitic domains. Such hydration processes are consistent with strain partitioning between water‐poor (less deformed) and water‐rich (intensely deformed) layers, consistent with changes in olivine and pyroxene crystallographic preferred orientations (CPOs). Our results support recent geophysical data from ultraslow spreading mid‐ocean ridge systems that fluids might penetrate beyond the stability of serpentine to depth between 6 and 15 km. Such peridotite shear zones act as fluid pathways for long‐lived detachment faults or oceanic transform faults, along which upper mantle rocks are exhumed to the seafloor. Fracturing and fluid flow along such peridotite shear zones might be recorded by deep microseismicity along ultraslow spreading ridges.

Micromachining of coarse-grained aluminum including crystallographic effects

This paper presents an experimental analysis of the effects of crystallographic anisotropy of the workpiece material when machining coarse-grained pure aluminum under varying cutting conditions. Orthogonal cutting experiments were conducted on an instrumented planning setup, and cutting forces and surface roughnesses were measured in a full-factorial experimental design. Cutting speed, uncut chip thickness (feed), and tool rake angle were varied at multiple levels. To determine the effect of subsurface deformation left by the previous tool passes, experiments were conducted both with and without cleanup cuts that reduce the surface deformation. The effect of crystallographic orientations and their interaction with cutting conditions on the specific cutting energy, the effective coefficient of friction, and the resulting surface roughness were analyzed through an analysis of variance approach. It was concluded that the crystallographic anisotropy has a strong effect in specific cutting energies, with up to 360% variation across different grains. Similarly, the roughness of the machined surface was seen to vary significantly (up to 831%) with the crystallographic orientations. On the other hand, the effective coefficient of friction was observed to be insensitive to the changes in crystallographic orientations. Lastly, a significant (up to 45%) difference in specific cutting energies was observed between the cases with and without cleanup cuts, indicating the strong presence and the influence of sub-surface deformation.

Dark-field X-ray microscopy reveals mosaicity and strain gradients across sub-surface TiC and TiN particles in steel matrix composites

Residual strain gradients and crystallographic mosaicity across embedded ceramic particles within metal-matrix composites have remained experimentally inaccessible. In this work, we use synchrotron dark-field X-ray microscopy to characterize strain and orientation gradients across ~20 µm large TiC and TiN particles embedded in a steel matrix annealed at 480 and 600 °C. The results document gradual crystallographic orientation changes across the particles and the presence of sub-grains, in contrast to electron backscatter diffraction data. These gradients appear, however, not directly correlated with the observed strain gradients, which are attributed mainly to the different strain states within particles’ interiors and envelopes.

Micromachining Imposed Subsurface Plastic Deformation in Single-Crystal Aluminum

In this work, we analyzed the nature and extent of deformation beneath the machined surface during orthogonal micromachining of single-crystal aluminum. We micromachined six different crystallographic orientations of a sample with [111] zone-axis and analyzed the sub-surface texture and resulting misorientations. The results indicate that the changes in crystallographic orientation induces variations in the depth of deformation, the degree of grain refinement and the lattice rotations. We observed up to 50% lattice rotations, shear bands varying from 55o to 60o from the direction of machining, and highly entangled dislocations, which confirmed the presence of strain hardening.