Influence Of Crystallographic Orientation Research Articles

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.

Influence of Crystallographic Orientation on the Deformation of Ag Nanoparticles During High-Speed Impact

Influence of Crystallographic Orientation on the Deformation of Ag Nanoparticles During High-Speed Impact

Role of Crystal Orientation, Temperature, and Strain Rate on the Mechanical Characterization of Nickel: An Atomistic-scale investigation

In this article, the influence of crystallographic orientation on the mechanical properties of pristine nickel (Ni) during uniaxial tensile deformation was explored by utilizing molecular dynamics simulations. To study the influence of [0 01] and [11 8 5] crystal orientations on the mechanical properties and microstructural evolution of pristine Ni, simulations were performed at different temperatures ranging from 100 K to 900 K and at strain rates ranging from 10 7 to 10 10 s–1. The results revealed that Ni with [11 8 5] orientation showed a higher elastic modulus than Ni with [0 0 1] orientation, whereas the yield strength of [0 0 1] orientation was higher than [11 8 5] orientation for a combination of temperatures and strain rates. Also, in comparison to [11 8 5] crystal orientation, the system with [0 0 1] orientation showed a high amount of dislocation density at the yield strain point for lower strain rates. At higher strain rates, the face-centered cubic to body-centered cubic transition was more prominent in the Ni system with [0 0 1] orientation, and it tends to decrease with the increase in temperature. Our present work may help materials scientists design materials with different crystal orientations that can perform according to the applied strain rates and temperatures. It is also proposed that tailoring of mechanical properties is achievable by exposing Ni with different crystal orientations to various environmental conditions (cryogenic, ambient, and elevated temperatures with different applied strain rates).

On the influence of crystallographic orientation on superelasticity - Fe-Mn-Al-Ni shape memory alloys studied by advanced in situ characterization techniques

The superelasticity of iron-based shape memory alloys is strongly influenced by microstructural features such as crystallographic orientation, size and morphology of grains, character of grain boundaries as well as volume fraction of precipitates. Furthermore, elementary processes such as formation of dislocations, interaction of dislocations with the austenite/martensite phase boundary, and the interaction of different martensite variants result in functional degradation. Advanced in situ characterization techniques like digital image correlation (DIC) and infrared thermography (IR-TG) corroborated by ex situ high resolution electron backscatter diffraction (HR-EBSD) and electron contrast channeling imaging (ECCI) were used to investigate the functional stability of the superelasticity of Fe–Mn–Al–Ni single crystals and oligocrystals under tensile and compressive loading. The early stabilization of martensite during repeated loading was attributed, besides other mechanisms, to the interaction of different martensite variants leading to the formation of dislocations, locally pinning the austenite/martensite interface.

Dislocation sub-structures, recovery and recrystallization in pure tantalum

Plastic deformation, static recovery and recrystallization in pure tantalum are analyzed in the present paper. Quantitative analysis of dislocation sub-structures were done. Sub-structures development is completely dependent on crystallographic orientation. No clear effect of recovery was observed when direct analysis was made. Hence, recovery was studied through its effect on recrystallization. Recovery heat treatments followed by a recrystallization heat treatment were applied to compare the recrystallized state of samples which were subject to prior recovery with those which were not. Results show that recrystallization is accelerated in the early stages of recovery (low temperature or low annealing time or low plastic strain). On the opposite, in the advanced stages of recovery, it slows down recrystallization. Results show again an influence of crystallographic orientation. Static recrystallization was also investigated and the influence of crystallographic orientation, most probably inherited from the deformed state through dislocation sub-structures, was observed. Based on experimental results, a discussion on the mechanisms of nucleation in the different orientation grains is presented. Finally, a discussion is made on the quantification of stored energy. The effect of the observation scale and the choices of considering dislocation density or dislocation sub-boundaries energies from EBSD data is discussed.

Significance of separations occurring in mechanical testing of thermomechanical rolled pipeline steels

In this study, the origin of separations is investigated in modern high strength pipeline steels. In-depth microstructure characterization and property correlation is used to demonstrate that preferred crystallographic planes are responsible for the generation of separations in thermomechanical rolled steels with high cleanliness. Further insights on the influence of crystallographic orientation are obtained by performing different types of standard and non-standard tests with specific specimen and notch orientations and evaluating the related crack propagation path. Finally, special texture components are identified, which determine whether in-plane fracture, splitting or deflection of the cleavage parts take place. This study assists in understanding the separation phenomenon in modern high strength pipeline steels across the different test methods. Furthermore, it amplifies that the separations in thermomechanical rolled steels with high steel cleanliness are inherently linked to the orientation of specific crystallographic planes and are not necessarily an indication of a poor material behavior.

Influence of crystallographic orientation and Al alloying on the corrosion behaviour of extruded α-Mg/LPSO two-phase Mg-Zn-Y alloys with multimodal microstructure

A highly corrosion resistant Mg-Zn-Y-Al alloy featuring an α-Mg/LPSO two-phase multimodal microstructure was developed. The extruded Mg-Zn-Y alloy showed orientation dependent corrosion behaviour, the longitudinal section exhibited a higher corrosion rate than the transverse section. The orientation dependence was attributed to the varying in-plane atomic densities of the crystallographic planes on the longitudinal and transverse sections. The LPSO phase was the cathode and galvanic corrosion occurred in the adjacent α-Mg. The Al alloying into the Mg-Zn-Y alloy facilitated the formation of a protective surface film, which decreased the corrosion rate in spite of geometrical and electrochemical heterogeneities.

Molecular dynamic modelling of the combined influence from strain rate and temperature at tensile loading of nanosized single crystal Cu beams

It is well-known and experimentally confirmed that the mechanical response of small enough structures, with linear measures typically below about 100 nm, differs from the response at macro scale. In addition to size effects, the crystallographic orientation of the material becomes increasingly important at this scale. This paper investigates the combined influence of strain rate and temperature on nanosized, initially defect-free, single crystal Cu beams of square cross-sections subjected to displacement-controlled tensile loading. Additionally, the influence of crystallographic orientation is investigated for loading along the [100], [110] or [111] direction. The simulations performed were 3D molecular dynamic simulations. Both the elastic and the plastic behaviours were analysed, and stress-strain curves and dislocation evolution were monitored in detail during loading.

Numerical modelling of size effects in micro-cutting of f.c.c. single crystal: Influence of strain gradients

A size effect is exhibited by metals in cutting processes at small scales: a nonlinear escalation in the cutting energy per unit volume with a decrease in the thickness of the uncut chip. To understand this phenomenon, a numerical model of orthogonal micro-cutting of f.c.c. single-crystal copper was developed, and three different depths of cut (0.8 μm, 1.4 μm and 2.0 μm) were considered. Enhanced models of crystal plasticity (EMCP) and strain-gradient crystal plasticity (EMSGCP) implemented in ABAQUS/Explicit through a VUMAT Fortran subroutine were used. Obtained results were compared with the experiments reported in the literature. The influence of size effect on deformation response of a single-crystal material was investigated extensively in terms of the distribution of field variables such as strain gradients, stresses, lattice rotations and activity of different slip systems. The influence of crystallographic orientation was also studied. It was observed that the size-effect phenomenon was predicted more accurately with the EMSGCP theory, where polar dislocations evolving during deformation were found to affect it significantly.

Effect of crystallographic orientation on mechanical properties of single-crystal CoCrFeMnNi high-entropy alloy

Using molecular dynamics (MD) simulation, the influence of crystallographic orientation on the mechanical properties and microstructure evolution of the single-crystal CoCrFeMnNi high-entropy alloy as a face-centered cubic (FCC) metal is explored and quantified by nanoindentation. At the elastic stage of P-h curve, the results of MD-simulation are almost consistent with that of Hertz contact theory fitting, which ensures the accuracy of our results. The plastic deformation is studied by correlating the P-h curve with the instantaneous defect structure, and dominated by nucleation of Shockley partial dislocations or the movements of stacking faults. Furthermore, we discuss the effects of crystallographic orientations [ 001 ] , [ 110 ] , and [ 111 ] on the mechanical response of materials and the microstructure evolution. The slip mode and the stress-concentrated region are controlled by the crystallographic orientations, and an obvious pop-in behaviors are viewed in [ 111 ] -oriented sample, without appearing in other samples. The microstructure evolution exhibits distinct anisotropy causing the discrepancy of dislocation density and hardness. By analyzing the evolution of dislocation density and hardness, the linear relationship between the square root of dislocations density and hardness is revealed, and in good agreement with the classic Taylor hardening expression where the pre-factor is strongly dependent on the crystallographic orientation. In the study, the atomistic results are consistent with those predicted by the classic continuum mechanical theory, which contributes to the application of classic mechanical theory in molecular dynamics simulation.

Influence of crystallographic orientation on the void growth at the grain boundaries in bi-crystals

Void growth and morphology evolution in fcc bi-crystals are investigated using crystal plasticity finite element method. For that purpose, representative volume element of bi-crystals with a void at the grain boundary are considered in the analysis. Grain boundary is assumed initially perpendicular/coaxial with the straight sides of the cell. Fully periodic boundary conditions are prescribed in the representative volume element and macroscopic stress triaxiality and Lode parameter are kept constant during the whole deformation process. Three different pairs of crystal orientations characterized as hard-hard, soft-soft and soft-hard have been employed for modelling the mechanical response of the bi-crystal. Simulations are performed to study the implications of triaxiality, Lode parameter and crystallographic orientation on slip mechanism, hardening and hence void evolution. The impact of void presence and its growth on the heterogeneity of lattice rotation and resulting grain fragmentation in neighbouring areas is also analysed and discussed.

Helium effects on the surface and subsurface evolutions in single-crystalline tungsten

Tungsten (W) has been perceived as one of the most promising plasma facing materials (PFMs) for future fusion reactors. In the past decade, its behavior under irradiation and helium (He) plasma interaction has been extensively studied. However, some key knowledge gaps still exist, such as the influence of crystallographic orientation on the surface and subsurface evolutions. In this work, we focus on the He ion-beam irradiation damage effects in mirror-polished single-crystalline W samples with three different surface planes of {100}, {110} and {111}. Irradiation was performed at room temperature using 40 keV He+ to a fluence of 1 × 1016/cm2, followed by thermal desorption spectroscopy (TDS) up to ~1920 K. The microstructures of He-irradiated W before and after TDS heat treatment were characterized by scanning and transmission electron microscopy. Subsurface He bubbles were imaged in all irradiated samples, but newly formed <111>-oriented surface grains and surface blisters were only observed in W {100} and {110} starting orientations. These results reveal that radiation damage, He thermal desorption, and surface/subsurface evolution are all strongly dependent on crystallographic orientation. Underlying physical mechanisms are discussed based on ion channeling effects, He-vacancy interactions, and surface diffusion. These findings provide new insights into He effects in W.

Influence of Crystallographic Orientation on Nanoscale Friction and Wear Mechanisms of the AZ91 Alloy

In the present study, nanoscale friction and wear behavior of the AZ91 alloy with respect to crystallographic orientations (basal, pyramidal and prismatic) were examined. The hardness of different crystallographic orientation was measured using nanoindentation. Load-dependent friction and wear behavior was investigated using atomic force microscopy (AFM). Electron back scattered diffraction (EBSD) was used to investigate the deformation behavior post-indentation and wear. A strong anisotropy in hardness, friction and wear with respect to crystallographic orientation was observed. The basal oriented grain was found to be most wear-resistant followed by prismatic and pyramidal oriented grains. The friction results corroborated the wear data. Additionally, the model proposed by Song et al. has been used to quantify the orientation dependence of friction values. Finally, it is anticipated that these results will enable the development of orientation informed surfaces for controlling the wear and friction response of materials.

Influence of Crystallographic Orientation on Creep Resistance of Single-Crystal Superalloy

Abstract This paper focuses on the influence of crystallographic orientation on creep resistance of CMSX-4 nickel-based superalloy. The single-crystal rods of CMSX-4 superalloy were manufactured with the use of the Bridgman method at a withdrawal rate of 3 mm/min. The crystallographic orientation of the rods was determined by the X-ray Ω-scan method with OD-EFG diffractometer and the Laue back-reflection technique. The creep tests were performed at a temperature of 982°C and the value of stress σ = 248 MPa. Microstructural investigation before and after the creep test of CMSX-4 superalloy was performed using a scanning electron microscope. The results showed that the distribution of the values of α angle strongly affects the creep resistance of a single-crystal superalloy.

Влияние кристаллографической ориентации на закономерности размерного эффекта при растяжении нанопроволоки молибдена

Влияние кристаллографической ориентации на закономерности размерного эффекта при растяжении нанопроволоки молибдена

Influence of crystallographic orientation and applied magnetic field on domain structure in duplex stainless steel studied using magnetic force microscopy

The paper investigates the local micro-magnetization behavior in duplex stainless steel (DSS) using magnetic force microscopy (MFM). DSS has equal amount of austenite phase in ferrite matrix. The MFM imaging clearly differentiates ferrite phase (ferromagnetic) from the austenite phase (paramagnetic) due to the maze type magnetic domains present in the ferrite phase. The magneto crystalline anisotropic effect on the domain structure is discussed with the support of electron backscatter diffraction (EBSD) measurements. The MFM phase contrast and domain width are correlated with the orientation of surface normal with respect to the easy axis of magnetization (〈100〉). The influence of external magnetic field (±127 kA/m) application on the domain structure is studied as a function of the grain orientation and the leakage field at the grain boundaries is analyzed based on the mis-orientation between the grains.

Incipient plasticity in tungsten during nanoindentation: Dependence on surface roughness, probe radius and crystal orientation

The influence of crystallographic orientation, contact size and surface roughness effects on incipient plasticity in tungsten were investigated by nanoindentation with indenters with a range of end radius (150, 350, 720 and 2800 nm) in single crystal samples with the (100) and (111) orientations. Results for the single crystals were compared to those for a reference polycrystalline tungsten sample tested under the same conditions. Surface roughness measurements showed that the Ra surface roughness was around 2, 4, and 6 nm for the (100), (111) and polycrystalline samples respectively. A strong size effect was observed, with the stress for incipient plasticity increasing as the indenter radius decreased. The maximum shear stress approached the theoretical shear strength when W(100) was indented using the tip with the smallest radius. The higher roughness and greater dislocation density on the W(111) and polycrystalline samples contributed to yield occurring at lower stresses.

Dependence of Crystallographic Orientation on Pitting Corrosion Behavior of Ni-Fe-Cr Alloy 028

The influence of crystallographic orientation on the pitting corrosion behavior of Ni-Fe-Cr alloy 028 was studied using a combination of X-ray diffraction (XRD), electron backscatter diffraction (EBSD), potentiodynamic polarization technique, and atomic force microscopy (AFM). The results show that there is anisotropy of pitting corrosion that strongly depends on crystallographic orientation of the surface plane. The distribution of pit density in a standard stereographic triangle indicates that the crystallographic planes close to {100} are more prone to pitting corrosion compared to planes {110} and {111}. The surface energy calculation of (001) and (111) shows that the plane with a high atomic packing density has a low surface energy with concomitant strong resistance to pitting corrosion. A correlation function between crystallographic orientation and pitting corrosion susceptibility suggests a method that not only predicts the pitting resistance of known textured materials, but also could help to improve corrosion resistance by controlling material texture.

Analysis of crystallographic orientation influence on thermal fatigue with delay of the single-crystal corset sample by means of thermo-elasto-visco-plastic finite-element modeling

The influence of a delay time at the maximum temperature on the number of cycles before the macrocrack initiation for two thermal loading programs was investigated for single-crystal nickel-based superalloy VZhM4. An analytic approximation of a delay time influence was proposed. Comparison of the computational results and analytic formula on the basis of constitutive equations with the experimental data was performed for various single-crystal nickel-based superalloys and showed a good accuracy. The influence of crystallographic orientation of the corset sample on the thermal fatigue durability with delay times was investigated for various thermal loading programs and single-crystal nickel-based superalloys.

Primary Ion-Irradiation Damage of BCC-Iron Surfaces

Using MD simulations, the influence of crystallographic orientation of an irradiated surface on the evolution of atomic displacement cascades is investigated in BCC-iron. The energy of atomic displacement cascades is varied from 1 to 20 keV. It is found that irradiation of the (111) surface results in crater formation while irradiation of the (110) surface gives rise to the formation of vacancy-type dislocation loops with the Burgers vectors а or a/2 . Both processes are associated with anisotropic propagation of the shock waves generated by the atomic displacement cascades. In the case of low energies of the latter, the number of point defects survived near the (110) surface is larger than that near (111). At higher energies, the influence of the free surface orientation on the number of survived defects decreases.