Effect Of Crystallographic Orientation Research Articles

The effect of crystallographic orientation on globularization and texture evolution during the annealing of a near α titanium alloy tube

In order to weaken the rolling texture of the cold-rolled tube and improve its secondary forming ability, this paper studies the influence mechanism of different annealing times on the microstructure and texture evolution of Ti-6Al-3Nb-2Zr-1Mo tube after intermediate-temperature annealing. The results show that as the annealing time increases from 30minutes to 120minutes, the degree of globularization of α/β phases significantly increases. The globularized structure mainly consists of equiaxed α particles, which are surrounded by necklace-like globularized β phases. The original rolling texture component did not change after 30-minute annealing. The intensity of the rolling texture was weakened, and two new components appear after 120minutes of annealing. The appearance of these two components was caused by the growing up of globularized α phases close to the Burgers orientation relationship (BOR) with surrounding β phases during a long annealing process. Moreover, it was observed that globularization to some extent broke the BOR between α phase and the adjacent β phase.

Effect of Initial Position and Crystallographic Orientation on Grain Selection Procedure in Z-Form Selector for Ni-Based Single-Crystal Superalloy.

The grain selection process in a Z-form selector for Ni-based single-crystal superalloy was simulated using a macro-scale ProCAST software (2013 version) coupled CAFE module combined with an experiment to investigate the grain selection procedure and mechanism with different grain positions and crystal orientation relationships. A non-stationary solidification process was found in the Z-form selector, and the liquid-solid (L-S) interface was tilted in the same direction as the selector channel during directional solidification. Given that the grain boundary was parallel to the Z-form selector, the overgrowth rate of the bi-crystal in the selector channel was very low. The initial position of the bi-crystal in the selector channel has a greater effect on the overgrowth rate than the effects of primary and secondary orientations. The grain selection was a result of the coupling of the competitive grain growth effect and geometrical restriction effect. Finally, the selection grain mechanism within the Z-form selector was discussed, coalescing the temperature field and the grain competition growth mechanism.

Effect of Crystallographic Orientation on the Formation of α-Case in Ti-6Al-4V Titanium Alloy

Effect of Crystallographic Orientation on the Formation of α-Case in Ti-6Al-4V Titanium Alloy

Influence of crystallographic orientation on electronic phase separation in manganite thin films

Thin film epitaxy is a powerful method to control the strain and crystallographic orientation of the thin films using epitaxial relationship with the substrate. For colossal magnetoresistive (CMR) manganites thin films, the strong correlation between spin, charge, orbital and lattice degrees of freedom make their physical properties depend sensitively on the choice of substrate. This is especially true when considering the fact that the physical behaviors of manganites are often governed by electronic phase separation (EPS) phenomena, whose physical origin is strongly tied to lattice strain distribution. While many studies have been conducted on the substrate lattice mismatch induced strain effect, research on the substrate crystallographic orientation effect on EPS has received less attention. In this work, using (La2/3Pr1/3)5/8Ca3/8MnO3 (LPCMO) films grown on SrTiO3 (STO) substrate as a protype system, we show that EPS and its associated physical properties are strongly affected by the substrate crystallographic orientations. Specifically, we observed a clear boost of ferromagnetism in (110)-oriented LPCMO thin films with elongated EPS domains. First principles calculations show that the magnetic phase transitions of LPCMO are dominantly influenced by the spin-lattice coupling.

Incipient Dissolution of Emplaced Forsterite and Fayalite Records the Effects of Climate, Mineral Composition, and Crystallographic Orientation

To investigate the effects of environment, composition, and crystal orientation on incipient surface alteration of forsterite and fayalite in a natural environment, polycrystalline forsterite and fayalite samples were emplaced in Mg/Fe-rich and Al-poor ultramafic soils under subarctic (Tablelands in Newfoundland, Canada; 3.9 ⁰C and ∼120 cm precipitation/year), Mediterranean (Klamath Mountains, California;≤12.8 ⁰C and ∼101-118 cm precipitation/year), and desert (Pickhandle Gulch, Nevada; ∼14.1 ⁰C and ∼14.4 cm/year) climates for one year. Incipient alteration after one year was examined using scanning electron microscopy, atomic force microscopy, electron backscatter diffraction, X-ray photoelectron spectroscopy, and visible and near-infrared reflectance spectroscopy.Alteration features on forsterite surfaces included flat-bottomed pits with steeply dipping walls likely developing on grain faces and representing surface retreat of individual grains and lining features likely developing along grain boundaries. Mg-leached surface layers formed under acidic to slightly alkaline conditions while Mg-enrichment was observed under alkaline conditions. Flat bottomed pit formation preferentially occurs on surfaces within 30° of perpendicular to the b-axis (on the [010] plane) of the olivine crystal lattice. Depth of flat-bottomed pits on forsterite surfaces follows the order Klamath Mountains > Tablelands >> Pickhandle Gulch, reflecting the importance of environmental conditions. Warm, wet, and relatively acidic conditions enhanced forsterite dissolution over cold, wet, and slightly alkaline conditions, with minimal alteration observed under hot but arid and alkaline conditions. Greater surface roughness on flat-bottomed pit floors on Klamath Mountain forsterite surfaces are consistent with less-saturated soil-pore water reaction conditions.In contrast, fayalite disks buried in the Klamath Mountains show no evidence for etch-pit formation despite the warm, wet, and slightly acidic conditions. Elevated Fe/Si ratios from X-ray photoelectron spectroscopy measurements and evidence of M-OH bonds in visual and near infrared spectra are consistent with formation of a Fe-enriched hydroxylated layer limiting fayalite surface area available for water-rock interaction and retarding fayalite dissolution during aqueous alteration under oxidizing conditions. These results differ from previous laboratory experiments that show enhanced dissolution of fayalite relative to forsterite, showing the effect of natural, oxic, unsaturated weathering zones. These results will be helpful for interpreting observations of this widely studied mineral, including from the planet Mars.

Channel engineering for optimizing the electro‐thermal characteristics in p‐type GAA nanosheet transistors

AbstractIn this paper, we report simulation results for capacitance–voltage characteristics and temperature distribution in the cross‐section of p‐type gate‐all‐around nanosheet channel using an in‐house developed numerical simulator. The effects of material, channel width, and crystallographic orientation on electrical and thermal properties of p‐type nanosheet transistor are comprehensively investigated. The effect of channel engineering is analyzed, by evaluating density‐of‐states, hole density, current densities as well as distributions of temperature in the channel cross‐section. Finally, the thermal reliability of the device is addressed in terms of thermal resistance. The density‐of‐states and the hole density distribution at the oxide/channel interface can well explain the effective intrinsic capacitance obtained from the simulation. The better uniformity of the hole density distribution across the cross‐section of (110)/[001] channel, shows good promise for less performance fluctuation in terms of the thermal reliability issue.

The effect of crystallographic orientation of α-Al2O3 on the wetting behavior and adhesion characteristics of aluminum droplets

To solve the problem of adhesion of aluminum fluid to the inner wall of the vacuum ladle in the aluminum electrolysis industry, molecular dynamics simulation is performed to research the wetting behavior of Al droplets on the surfaces of the α-Al2O3 substrates C (0001), M ( 11ˉ00 ), and R ( 11ˉ02 ) at 1073 K. Meanwhile, the adhesion characteristics of the Al droplet are evaluated by the potential of the mean force (PMF) for the separation of the Al droplets from different surfaces of the α-Al2O3 substrate. The results show that the wetting behavior of Al droplets on the α-Al2O3 substrate is influenced by the different crystallographic orientations. The diffusion of Al droplets in the x-o-y plane of the substrate exhibits isotropic. The PMF and the interfacial potential energy reveal that the magnitude of the adhesion work in the solid-liquid separation of Al droplets from α-Al2O3 substrates follows the order C (0001) > R ( 11ˉ02 ) > M ( 11ˉ00 ). These findings characterize the wetting properties and adhesion behavior of Al droplets on an atomic scale and provide a theoretical basis for the selection of materials for the inner wall of the vacuum ladle.

Effect of crystallographic orientation on the potential barrier and conductivity of Bessel written graphitic electrodes in diamond

Ultrafast laser micromachining can be used to promote diamond graphitization, enabling the creation of electrically conductive wires embedded in the diamond matrix. In this context, the presence of a potential barrier in the conductivity of transverse graphitic wires fabricated by pulsed Bessel beams without sample translation across 500 μm thick monocrystalline CVD diamond has been studied. In particular, the role of the crystallographic orientation has been analysed. The morphology and the conductivity of the obtained electrodes have been studied using optical microscopy and current-voltage measurements, while the structural changes have been investigated by means of micro-Raman spectroscopy. By using different laser writing parameters, we have explored the features of different electrodes in a (100) and a (110) oriented diamond crystal respectively. We show that in addition to the use of specific pulse energies and durations (in the fs and ps regimes), the crystallographic orientation of the sample plays an important role in reducing or eliminating the potential barrier height of the IV electrical characterization curves. In a (110) oriented sample, it is possible to eradicate the potential barrier completely even for graphitic wires fabricated at low pulse energy and in the fs pulse duration regime, in contrast to the (100) oriented-crystal case where the barrier is generally observed. The effect of thermal annealing of the diamond samples on the resistivity of the fabricated micro-electrodes has also been investigated. In (110) oriented diamond, resistivities lower than 0.015 Ω cm have been obtained.

Numerical study on the effect of crystallographic orientation on mechanical behavior and its anisotropy of laser powder bed fusion AlSi10Mg

Anisotropic strength and ductility are limiting factors for the application of laser powder bed fusion AlSi10Mg. Previous efforts were devoted to explaining the origins of anisotropy mainly from the geometrical orientations of the Al-Si cellular structure and melt pool border, but the effect of crystallographic orientation is still unexplored. The present work aims to assess the mechanical behavior of Al-Si cellular structure using crystal plasticity model, with a focus on how grain orientation affects strength, damage initiation and their anisotropy. Forty-four crystallographic orientations were generated and assigned to a representative volume element resembling the real Al-Si cellular structure. For each orientation, simulations of uniaxial tension along the building direction and the perpendicular direction were performed. It is found that the grain orientation has a huge influence on both strength and damage sensitivity. Nevertheless, the correlation between strength and orientation cannot be established with the Schmid or Taylor factors due to the influence of the elongated Si network. Comparing the results for the two loading directions, strength anisotropy is revealed to present a weak dependence on grain orientation, whereas damage anisotropy varies significantly in the orientation space. The findings of this work can be used for up-scale modeling of mechanical behavior of additively manufactured AlSi10Mg.

(Second Best Paper Award) Preferred Grain Orientation to Enhance Interdiffusion at Room Temperature in Atomic Diffusion Bonding: A Fundamental Study Using Ni and Cu Films

Atomic diffusion bonding (ADB) of wafers using thin metal films is a promising process to achieve room-temperature wafer bonding [1,2]. During ADB processing, the bonding performance is enhanced by crystal lattice rearrangement, which occurs when two film surfaces mutually contact at room temperature. It is reasonable to infer that the degree of the interdiffusion of the two films at the bonded interface, including crystal lattice rearrangement, depends on the surface roughness and crystallographic grain orientation of the metal films used for bonding. For this study, after Ni film and Cu film were bonded using ADB, the interdiffusion at the bonded Ni/Cu film interface was examined quantitatively using values of saturation magnetization M s. We assessed the effects of crystallographic preferred grain orientation on the interdiffusion thickness at the bonded interface.The Ni film thickness was fixed at 20 nm, but the Cu film thickness was varied from 5 nm to 300 nm. For both films, Ta underlayer films were used. Surface roughness S a, as estimated using AFM of Ni(20 nm) film, was 0.25 nm. The value of S a for Cu films increased from 0.21 nm to 0.85 nm as the Cu film thickness was increased from 5 nm to 300 nm. XRD findings revealed that both Ni and Cu films showed the (111) preferred grain orientation, but the orientation was degraded at Cu thicknesses of less than 50 nm. Figure 1 presents a STEM cross-section image of bonded Ni(20 nm)/Cu(50 nm) films as an example: no vacancy was observed at the bonded interface. Figure 2 presents values of the interdiffusion thickness T ID for bonded films as a function of the Cu film thickness. T IDshowed a maximum of 6.5 nm for a 50-nm-thick Cu film. S a decreased as the Cu thickness decreased from 50 nm. However, T ID decreased remarkably. Results suggest that deterioration of the (111) preferred grain orientation of Cu films with reduction of film thickness degraded the interdiffusion at the Ni/Cu bonded interface.To support this assumption, Ti underlayers were used underneath Ni(20 nm) and Cu(10, 20 nm) films to enhance the degree of the (111) preferred grain orientation of these films. Results indicate that T ID at the Ni(20 nm)/Cu(10 nm) bonded interface was enhanced to 5.4 nm, which was one order greater than that of the bonded films with Ta underlayers, indicating that enhanced bonding performance of ADB can be achieved with low surface roughness and a high degree of (111) preferred grain orientation. This enhancement is expected to be obtained also via ADB processing using other metal films having an fcc crystal structure, such as Au, Ag, and Al. T. Shimatsu and M. Uomoto, J. Vac. Sci. Technol., B 28, 706 (2010).T. Shimatsu and M. Uomoto, ECS Trans., 33 (4), 61 (2010). Figure 1

Calculation of Precision Measure and Effect of the Sample Crystallographic Orientation on the Charge Kinetics of MgO Single Crystals Subjected to keV Electron Irradiation

Calculation of Precision Measure and Effect of the Sample Crystallographic Orientation on the Charge Kinetics of MgO Single Crystals Subjected to keV Electron Irradiation

Fatigue crack growth behavior of an additively manufactured titanium alloy: Effects of spatial and crystallographic orientations of α lamellae

Laser-based directed energy deposition (LDED) enables the rapid near-net-shape fabrication of large-scale titanium components for aerospace applications. However, the fatigue failure of the LDED-produced titanium alloys hinders their widespread use in critical load-bearing structures subjected to cyclic loading. Here, we investigate the fatigue crack growth behavior of LDED-produced Ti-6Al-2Zr-Mo-V alloy in both as-deposited and heat-treated states. The two states of samples consist of α and β laths with the majority of α laths showing distinct crystallographic and spatial orientations. They show distinct cracking behaviors: (i) Fatigue cracks with lengths lower than ∼400 µm grow along α/β boundaries and are surrounded by limited plastic deformations in the as-deposited sample, while in the heat-treated sample, they grow along basal or prismatic planes of the α lamellae associated with substantial plastic deformations; (ii) Fatigue cracks with lengths over ∼400 µm are primarily deflected by α/β boundaries in the as-deposited sample, but are retarded by severe plastic deformations in the heat-treated sample; (iii) Secondary cracks appear along the α/β boundaries in the as-deposited sample, whereas in the heat-treated sample they initiate in the interior and preferentially along the prismatic plane of the α lamellae due to localized shearing and plastic deformation. The fatigue crack growth behaviors are strongly correlated with orientations (both crystallographic and spatial ones) and the size of the α lamellae in the titanium samples. These findings highlight the significance of simultaneously tuning the spatial orientations of α lamellae and their crystallographic orientations to enhance the fatigue crack growth resistance of LDED-produced titanium alloys.

EFFECT OF CRYSTALLOGRAPHIC ORIENTATION ON MATERIAL REMOVAL BEHAVIOR DURING HIGH SPEED SCRATCHING OF MONOCRYSTALLINE SILICON

Monocrystalline silicon has anisotropic attributes due to asymmetric and non-uniform interatomic lattice structures, which affects its deformation and fracture properties. This paper aims to investigate the effect of crystallographic orientation on the material deformation and removal behavior during high speed scratching of monocrystalline silicon. A high-speed scratching setup is developed which can achieve the highest scratching speed of 40 m/s. Inclined scratching experiments are conducted on (001), (110) and (111) crystallographic planes over the speed range of 1 m/s to 30 m/s. As the scratching depth increases, the ductile-to-brittle transition of silicon at different crystallographic orientations are analyzed. The experimental results suggest that scratching in the direction of "[" ¯("1" ) "10]" on (111) plane presents the largest critical residual depth of ductile-to-brittle transition. Phase transformation from Si-I to the phases of Si-IV and a-Si dominates ductile deformation of silicon during scratching process, while scratching tests in "[" ¯("1" ) "10]" direction on (111) plane demonstrates the largest degree of material amorphization. This study can provide guidance for optimizing processing parameters of monocrystalline silicon components with different crystallographic orientations.

Effects of crystallographic orientation and lamellar configuration on fatigue crack propagation in single-colony structures of Ti–6Al–4V alloy: Alternating shear crack growth vs. damage accumulation crack propagation

In this study, the fatigue crack propagation mechanisms in lamellar colonies of Ti–6Al–4V alloy were examined using miniature compact-tension specimens with a single-colony structure at the crack tip. Fatigue tests were performed on colonies with different α-phase crystallographic orientations and lamellar configurations with respect to the notch plane and direction, followed by post-fatigue metallographic analysis. Crack propagation occurs by three main mechanisms: 1) alternating shear due to in-plane prismatic slip, 2) damage accumulation via dislocation–dislocation interaction due to out-of-plane slip, and 3) interlamellar decohesion due to damage accumulation via lamellar interphase boundary–dislocation interaction. The slope of da/dN vs. ΔK is higher for alternating shear crack growth than for damage accumulation crack propagation via dislocation–dislocation interaction. This is due to an incubation period before substantive crack extension in the latter case, which is dominated by degree of strain accommodation associated with the activated slip systems. When the lamellar interphase boundaries are nearly perpendicular to the loading axis, the crack growth rates drastically increase by interlamellar decohesion. This is attributed to the reduced incubation period due to slip incompatibility at the interphase boundary where numerous crack nuclei were formed during damage accumulation process.

Identify key serpentines antigorite, lizardite and chrysotile with various compositions and crystallographic orientations using micro-Raman spectroscopy

Serpentines are geologically important minerals, and antigorite (Atg), lizardite (Lz) and chrysotile (Ctl) are the three key varieties. Their quick and accurate identification with micro-Raman spectroscopy requires to consider the effects of different crystallographic orientations and different chemical compositions. By collecting from existing literatures all Raman spectroscopic data and compositional data acquired from the same or identical Atg, Lz and Ctl samples, we critically examined the compositional effects for the first time, and found that some compositional parameters like the Al2O3 and Cr2O3 contents have significant impacts on the Raman features. Taking into account the effects of both compositional difference and crystallographic orientation difference, we propose two identification schemes for Atg, Lz and Ctl: the first one uses those weak but characteristic Raman peaks at 1200–1000 cm−1, and the second one uses those intense and unanimously-observed Raman peaks at ∼688, 378 and 229 cm−1. As for the first identification scheme, no peak at 1200–1000 cm−1 suggests the presence of Lz; a single peak at ∼1045, at ∼1070, or at ∼1106 cm−1 indicates the presence of Atg, Lz, or Ctl, respectively; two Raman peaks at ∼1040 and 1070 cm−1 implies the presence of Lz; the occasionally observed one single peak at ∼1040 cm−1 may imply the presence of either Atg or Lz, which can be sought out by resorting to the peak position ratio R∼1045/688 (Atg having R∼1045/688 > ∼1.521 whereas Lz attaining R∼1045/688 < ∼1.521). As for the second identification scheme, Atg can be readily separated from Lz and Ctl by using the exact wavenumbers of the Raman peaks at ∼688 and ∼378 cm−1, and Lz and Ctl can be further discriminated by using the exact wavenumbers of the Raman peaks at ∼378 and ∼229 cm−1. Under most circumstances, both identification schemes do not require the information of crystallographic orientation or composition, and can be conveniently applied to identify the serpentines of Atg, Lz and Ctl.

Shock response of single crystal rhenium: Effect of crystallographic orientation

Rhenium, a unique engineering material with the second highest melting point of all metals, has significant application potential in harsh service environments, and thus evaluating its mechanical responses under shock loadings is of great importance. Through molecular dynamic simulations, we have systematically investigated the effect of crystallographic orientations on the mechanical responses of single crystalline rhenium under shock compression. We have obtained the P–V/V0, Up-P, P-T, and Us-Up Hugoniot relations, and evaluated their anisotropies. The particle velocity, Pzz, and shear stress show orientation dependent when tracing the shock profiles at different time, and the difference is particularly pronounced for shear stress, resulting from the atomic arrangement in the HCP crystal structure of rhenium. The plastic deformations mechanisms of rhenium single crystal under shock loadings are revealed as the emission of dislocations and the generation of disordered atoms, and the influence of shock intensity on the plastic deformation mechanism has been systematically studied. The results presented in this work not only shed light on the effect of crystallographic orientations on the mechanical responses of monocrystalline rhenium under shock compression, but also offers fundamental insights for understanding the shock induced plastic deformation mechanisms, which could provide a valuable supplement to the investigations of mechanical properties pertaining to rhenium.

Effect of specimen size and crystallographic orientation on the nano/microscale mechanical properties and deformation behavior of CrCoNi medium-entropy alloy

CrCoNi medium-entropy alloy (MEA) shows an exceptional combination of macroscale mechanical properties, however, knowledge of its mechanical properties at nano/microscale is lacking. In this paper, nano/microscale single crystal MEA pillars with orientation of 〈116〉, 〈014〉, 〈102〉 were fabricated using focused ion beam milling, and the compressive strength was determined with micropillar compression testing using a flat-end tip in an indentation machine. Results showed that the yield and flow strength of these MEA pillars were orientation-dependent, i.e., the lower the Schmid factor, the higher the strength. At the same time the strength of the pillars was dependent on the pillar’s size, the strength increasing as the pillar diameter reduced. From the results of the micropillar compression testing, the bulk critical resolved shear stress (CRSS) was determined to be 92 MPa, which is the highest value of the group of CrCoNi-based medium and high-entropy alloys. Analysis of transmission electron microscope images and large-scale molecular dynamics simulations revealed a group of complimentary deformation mechanisms, including dislocation slides, dislocation annihilation, dislocation-slip band interaction, formation of nanoscale stacking-faulting networks, and deformation nanotwins.

Anisotropy in flow behaviour of directionally solidified Ni-based superalloy under compression at an elevated temperature

Directionally solidified (DS) superalloys consist of coarse columnar grains with <001> preferred orientation parallel to the maximum stress axis; but, grain orientations in the transverse direction are not controlled. However, during service, substantial loading could occur in the transverse direction as well, leading to early intergranular failure of components such as DS turbine blades. The present study investigates the effect of crystallographic orientation as well as specimen orientation (transverse and longitudinal with respect to grain growth direction) on the mechanical response of DS Ni-based superalloy in compression. Compression tests were performed at 700 ºC on transverse (with predominantly <101> or <001> oriented grains) and longitudinal (with <001> oriented grain) samples. Though there were negligible changes in yield stress, variations in hardening behaviour and ductility were observed in all the tested samples. Unlike transverse samples, longitudinal samples showed significant strain hardening with no failure even up to 0.3 true strain. Deformation mechanisms that led to these differences are identified using advance characterization techniques. γ' shearing with antiphase boundary formation was observed in the sample containing <101> grains, whereas γ' shearing with the formation of superlattice intrinsic stacking faults occurred in the sample having <001> grains. In addition, substantial lattice rotation and deformation twinning also contribute to strain hardening, especially in longitudinal samples. The effect of orientation is explained in terms of effective stacking fault energy. The study suggests that grains with <001> orientation undergo significant strain hardening and thereby accommodate large strain as compared to <101> oriented grains in DS alloys.

Effect of crystallographic orientation on the phase transition of a finite TiNi shape memory alloy wafer.

Effect of crystallographic orientation on the phase transition of a finite TiNi shape memory alloy wafer.

Pioneering Enhanced Corrosion Resistance along the Normal Plane of an Ultra-Light Mg-Li Extruded Sheet.

The microstructure and corrosion anisotropy of the Mg-5Li extruded sheet were investigated in this work. Three distinct samples cut from the normal plane (A), longitudinal plane (B), and cross-sectional plane (C) of the as-extruded sheet were prepared. The microstructure was analyzed using optical microscopy (OM), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The corrosion resistance and behaviors of the three samples in a 0.1 mol/L NaCl solution were evaluated by employing hydrogen evolution, mass loss testing, electrochemical assessments, and corrosion morphology analyses. The results revealed that sample A displayed a distinctive bimodal (0002) basal texture, along with clearly distinguishably larger grain sizes than the other samples. The effect of grain size and crystallographic orientation on the corrosion resistance was highlighted, indicating the pioneering corrosion resistance of sample A and the lowest corrosion resistance of sample C. Furthermore, all three samples exhibited the characteristic filiform corrosion during the initial stages of corrosion, progressing into the formation of corrosion pits, with sample C displaying pronounced susceptibility.