Anisotropy Of Interfacial Energy Research Articles

Morphological diversity in directionally-solidified microstructures with varying anisotropy of solid-liquid interfacial free energy

Morphological diversity in directionally-solidified microstructures with varying anisotropy of solid-liquid interfacial free energy

Perpendicular magnetic anisotropy in permalloy ultrathin film grown on RuO2(101) surface

Permalloy (Py) films are commonly regarded as soft magnetic materials, wherein the magnetization aligns within the film plane. Our studies reveal the presence of perpendicular magnetic anisotropy in Py thin films deposited on the collinear antiferromagnetic RuO2(101) surface. By employing both the magneto-optical Kerr effect and the anomalous Hall effect, we identified the interfacial origin of the observed perpendicular anisotropy, quantifying it with an interfacial anisotropy energy of approximately 0.77 erg/cm2. Current-induced magnetization switching in Py/RuO2(101) has been achieved under an in-plane field, with the current applied along both [010] and [10 1¯] directions. Py films exhibiting perpendicular magnetic anisotropy offer an innovative material platform for investigating the spin–orbit effect, holding significant potential for spintronics applications.

Inclined θ′ precipitates with terraced Cu/Mn-rich multilayers in Al–Cu alloys

In this work, an inclined θ′ morphology with terraced Cu/Mn-rich multilayers is observed in Al–Cu based alloys. The GPA (geometric phase analysis) results indicate that the inclined (∼3.1°) θ′ precipitates could induce significant lattice distortion at the interface. The chemical analysis results demonstrate that Mn atoms could get into the coherent (001)θ′//(001)Al interface with large misfit strains, which may contribute to maintaining the coherent relationship of the (001)θ'//(001)Al interface. Additionally, the interfacial energy between coherent Cu/Mn-rich (001)θ'//(001)Al interface and semi-coherent (010)θ′//(010)Al interface is more closer than that of the normal (001)θ'//(001)Al interface, suggesting a weakness of the anisotropic interfacial energy of θ′ with Cu/Mn-rich layers. The phase field simulation results suggest the formation of inclined θ′ precipitates when elastic strain energy dominates the θ′ morphology. Therefore, the inclined morphology of θ′ precipitates with terraced Cu/Mn-rich multilayers is a plausible outcome in Al–Cu alloys.

Atomistic insight into dendrite growth orientation transition in Al-Cu alloy

In this study, we investigate the impact of solid-melt interfacial energy anisotropy on the microstructure of components. Our focus is on the Al-Cu system's Al-rich side, where we compute the solid-melt interfacial free energy and its anisotropy using Molecular Dynamics (MD) simulations. Our findings reveal that, as the Cu concentration in the melt increases, the preferred dendrite growth orientation shifts from <100> to <110>. Furthermore, atomic density profile analysis shows an improvement in ordering in the (110) plane at higher Cu concentrations. Our results suggest that the transition in dendrite growth orientation is a consequence of the weakened anisotropy between (100) and (110) interfacial energies at higher Cu concentrations and undercooling temperatures. We also observe displaced atomic density profiles between Al and Cu atoms in proximity to the interface. We propose that a displaced atomic density profile between solute and solvent atoms could be a characteristic feature of systems undergoing a dendrite orientation transition.

Influence of surface energy anisotropy on nucleation and crystallographic texture of polycrystalline deposits

This paper aims to elucidate the role of interface energy anisotropy in orientation selection during nucleation of new grains in a polycrystalline film growth. An assessment of (heterogeneous) nucleation probability as function of orientation of both the bottom grain and of the nucleus was developed (using the concepts of classical nucleation theory). Novel solutions to the generalized Winterbottom construction were described in cases of very strong anisotropy and arbitrary orientations. In order to demonstrate the effect on the film crystallographic texture, a 2D Monte Carlo algorithm for anisotropic polycrystalline growth was used to simulate growth of films with columnar microstructure. The effect of strength of anisotropy, the deposition rate and initial texture were investigated. Results showed that with larger strength of anisotropy, the nucleation rate is less dependent on the driving force, but more dependent on the initial texture. With certain initial textures, the anisotropic nucleation may even be either impossible or having probability close to one irrespective of the driving force. Depending on the conditions, the anisotropic nucleation could hasten the evolution towards the interface-energy minimizing texture or retard it. Based on these insights, a hypothesis was offered to explain a peculiar texture evolution in electrodeposited nickel.

Strong cooperation growth of two phases in the ternary eutectic

The growth mechanism and tensile performance of ternary Ni40.6Fe36.4Ti23 alloy were investigated using directional solidification technique. The ternary Fe2Ti+γ-Fe(Ni)+Ni3Ti eutectic formed a lamellar structure under the steady state growth. After quenching, the Fe2Ti phase transformed into independently grown fiber while the γ-Fe(Ni) and Ni3Ti phases kept lamellar structure. It was confirmed that the solid/solid interfacial energy anisotropy contributed to the strong cooperation growth of the two phases in the ternary eutectic. The γ-Fe(Ni)/Ni3Ti interface preferred to be parallel to the common planes of {111}γ and {0001}Ni3Ti with low interfacial energy, leading to the formation of the stable lamellar structure under different solidification conditions. Owing to the reduction of transverse grain boundaries and grain refinement, the alloy solidified at 10 μm/s growth velocity showed the highest tensile strength and Young's modulus with translamellar fracture mechanism.

Multivariant microstructure evolution in Ti-alloys: insights from a quantitative phase-field study

Abstract In the present work, we employ a CALPHAD-integrated physics-based quantitative multi-phase field model to study the microstructure evolution in a multi-phase Ti-alloy. In this model we use the free energies obtained from TTTI3 thermodynamic database for Ti-based alloys using a CALPHAD approach. For numerical implementation of the model, we solve the governing equations in their weak form using the open-source MOOSE finite element framework. Our model is successfully able to capture all the possible orientational variants in Ti- alloy system. Moreover, we elucidate the complex interaction between the variants using two- and multi-particle simulations. We show that the elastic energies associated with the variants play significant role in their growth behavior. We also explore the effect of anisotropy in interfacial energy on the variant evolution.

Experimental determination of solid-liquid interfacial free energy anisotropy in Al-Zn via equilibrium droplet method

The increasing Zn content causes dendrite orientation transition during solidification of Al-Zn alloys, which is supposed to be related to the change of solid-liquid interfacial energy anisotropy. In this paper, experimental measurements of the interfacial energy anisotropy were performed in Al-17, 30 and 75wt.%Zn alloys with equilibrium droplet method. Droplets shape in relation to crystal orientation and droplets morphology are obtained by Electron Back-Scatter Diffraction and X-ray Computed Tomography, respectively. The result indicates that anisotropic parameters ε1 and ε2 both decreases with increasing Zn concentration and the directions of maximum interfacial energy transform from 〈100〉 directions in Al-17wt.%Zn and Al-30wt.%Zn to 〈110〉 directions in Al-75wt.%Zn. In addition, the Wulff plot and normalized interfacial stiffness are quantified and compared with the corresponding Al-Zn dendrites orientation selection.

A combined simulation and experimental study of the equilibrium shapes of η′ and α precipitates in Mn-containing 7xxx Al-alloys

The addition of Mn to 7xxx series Al-alloys helps improve tensile properties owed to the presence of α precipitates (Al(Mn,Fe)Si, simple cubic, 50–200 nm, non-shearable) in addition to the η′ precipitates (Mg2Zn5−xAl2+x, hexagonal, 4–6 nm, shearable) commonly observed in the 7xxx series Al-alloys. The coexistence of multiple α and η′ variants, 24 for α and 4 for η′, coupled with their small size-scale, makes the experimental determination by x-ray diffraction (XRD) and scanning transmission electron microscopy (STEM) challenging. This work formulates a phase-field model to predict precipitate shapes in three-dimension (3D) using experimental characterization as inputs to create virtual precipitate cross-sections for use in morphological comparison with experimental 2D (S)TEM images. Based on the atomic structures and orientation relationships observed in the experiments, the lattice site correspondences between the matrix and the two precipitate phases are derived, which are required for the prediction of shapes of coherent precipitates. Systematic phase-field simulations are then carried out to document the 3D shapes for all possible variants, as well as the corresponding 2D cross-sectional shapes when observed parallel to low-index matrix planes. These 2D cross-sectional shapes are compared with high-angle annular dark-field STEM (HAADF-STEM) images, which demonstrates that the identification of Mn precipitate type is possible by such comparisons. This helps unravel some of the complications encountered when characterizing precipitate microstructures in Mn containing Al-alloys by STEM. Finally, the equilibrium shapes as a function of precipitate size and the effect of interfacial energy anisotropy are investigated.

Numerical modeling of faceted crystal growth using a lattice Boltzmann-phase field model with a new interfacial energy function

A lattice Boltzmann-phase field model is proposed to study faceted crystal growth in a supersaturated solution, taking into account a new anisotropic interfacial energy function to reproduce the facet characteristics. In this model, a flow field solver and a concentration field solver are coupled with the phase field equation to study faceted crystal growth with fluid convection and solute transfer. Qualitative and quantitative comparisons are carried out with the experimental observation and theoretical analysis of snowflakes to demonstrate the validity and accuracy of the present numerical method. Then crystallization of sodium chloride in a supersaturated solution is investigated in a 3D space at a constant temperature. The results show that the initial supersaturation, solute depletion rate, and solution flow can greatly change the faceted crystal growth by affecting solute transport and distribution. The mechanism of the formation of morphologies and interface velocity evolution is studied and concluded, which shows that the present model has instructional significance for studying and understanding the regulation mechanism of faceted crystal growth.

High order accurate and convergent numerical scheme for the strongly anisotropic Cahn–Hilliard model

AbstractWe propose and analyze a second order accurate in time, energy stable numerical scheme for the strongly anisotropic Cahn–Hilliard system, in which a biharmonic regularization has to be introduced to make the equation well‐posed. A convexity analysis on the anisotropic interfacial energy is necessary to overcome an essential difficulty associated with its highly nonlinear and singular nature. The second order backward differentiation formula temporal approximation is applied, combined with Fourier pseudo‐spectral spatial discretization. The nonlinear surface energy part is updated by an explicit extrapolation formula. Meanwhile, the energy stability analysis is enforced by the fact that all the second order functional derivatives of the energy stay uniformly bounded by a global constant. A Douglas‐Dupont type regularization is added to stabilize the numerical scheme, and a careful estimate ensures a modified energy stability with a uniform constraint for the regularization parameter . In turn, the combination with an appropriate treatment for the nonlinear double well potential terms leads to a weakly nonlinear scheme. More importantly, such an energy stability is in terms of the interfacial energy with respect to the original phase variable, which enables us to derive an optimal rate convergence analysis.

Mechanistic Exploration of Dendrite Growth and Inhibition for Lithium Metal Batteries

Li metal has been considered an ideal anode in lithium batteries due to its high theoretical capacity of 3860 mAh·g−1 and lowest negative reduction potential of −3.040 V among the standard hydrogen electrodes. However, lithium dendrites can easily grow on the surface of the negative electrode during charging, which results in a short circuit of the battery and reduces its efficiency. This paper investigated dendrite growth and inhibition mechanisms in lithium metal batteries to improve battery life. The impacts of the initial nucleation spacing, surface energy anisotropy strength, and interfacial electrochemical driving force on lithium dendrite growth were analyzed with electrochemical experiments and mathematical models. The results showed that the smaller nucleation spacing inhibits the growth of dendrite side branches and reduces the roughness of lithium metal deposition on the negative electrode. A lower interfacial energy anisotropy strength can slow down the growth of dendrite tips and improve the dendrite growth structure. The growth of the dendrites is influenced by the interfacial electrochemical driving force. Reducing the nucleation overpotential can effectively inhibit the growth of lithium dendrites.

Strain-Driven Faceting of Graphene-Catalyst Interfaces.

The interfacial interaction of 2D materials with the substrate leads to striking surface faceting affecting its electronic properties. Here, we quantitatively study the orientation-dependent facet topographies observed on the catalyst under graphene using electron backscatter diffraction and atomic force microscopy. The original flat catalyst surface transforms into two facets: a low-energy low-index surface, e.g. (111), and a vicinal (high-index) surface. The critical role of graphene strain, besides anisotropic interfacial energy, in forming the observed topographies is revealed by molecular simulations. These insights are applicable to other 2D/3D heterostructures.

Growth Mechanism of Ice Crystals with Five-Fold Symmetry by the Phase-Field Method

In order to simulate the ice crystal growth with five-fold symmetry, a new phase-field model was established. The finite difference method was used to solve the governing equation, reproduce the growth morphology of ice crystals with five-fold symmetry, and study the influence of interfacial energy anisotropy and undercooling on the growth mechanism of ice crystals. The results indicate that when the strength of interfacial energy anisotropy ( ε 5 ) is greater than the critical value (1/24), the interface discontinuity and corners form at the tips of the main stem and side branches. The characteristic parameters of the ice crystal tip in the horizontal direction have an extreme value at ε 5 equal to 0.1. With an increase in undercooling, the main branch becomes slender and side branches appear, which is consistent with the mechanism of crystal continuous growth. When undercooling reaches 0.4, ice crystal growth changes from diffusion control to dynamic control. Therefore, by selecting the quick freezing conditions, undercooling is controlled at around 0.4 and the interfacial energy anisotropy at around 0.1, and the tip radius of curvature is minimized so as to prevent large ice crystals from damaging the cell wall and leading to the decline in the quality of quick-frozen food. The findings of this study can help us have a better understanding of ice crystal growth in the process of quick-frozen food preservation.

Influence of La addition on Fe-rich intermetallic phases formation and mechanical properties of Al-7Si-4Cu-0.35Mg-0.2Fe alloys prepared by squeeze casting

Brittle β-Al5FeSi (β-Fe) intermetallic phases directly affect the mechanical properties of Al–Si alloys; thus, it is essential to modify these phases. Scanning electron microscope analysis showed that rare earth Lanthanum (La) additions (0, 0.15, 0.30 and 0.50 wt%) had a refining effect on β-Fe phases in Al–7Si–4Cu-0.35Mg-0.2Fe (wt.%) alloys prepared by squeeze casting. The underlying refinement mechanisms of rare earth La on the β-Fe were discussed in terms of experimental observations, nucleation thermodynamics and growth kinetics. For nucleation thermodynamics, La additions could induce the formation of La-rich intermetallic phases Al4Cu2SiLa with orthorhombic structure. Because β-Fe nuclei had a good lattice matching and epitaxial relationship with the Al4Cu2SiLa phases, the Al4Cu2SiLa provided energetically favorable nucleation sites for β-Fe and greatly promoted the nucleation of β-Fe in alloys. Meanwhile, the added La atoms could restrain the diffusion of atoms to the solid/liquid interface front and alter the β-Fe interfacial structure and energy, therefore restricting the β-Fe growth. Furthermore, β-Fe/Al4Cu2SiLa grew into side-by-side and cross-like morphologies, and its growth behaviors were controlled by solute concentration and anisotropy of the solid-liquid interfacial energy in a cooperative eutectic reaction. In addition, different fracture behaviors from brittle fracture to mixed ductile fracture and quasi-cleavage brittle fracture were also illustrated with increasing La addition, and these fracture behaviors were influenced by the characteristics of brittle La-rich and β-Fe intermetallic phases. When the addition of La was increased to 0.3 wt% and 0.5 wt%, it occurred quasi-cleavage brittle fracture, which was caused by the precipitation of coarse plate-like La-rich phases.

Phase-field computations of anisotropic ice crystal growth on a spherical surface

In this paper, we present a numerical method for the phase-field model of anisotropic ice crystal growth on a spherical surface. The mathematical model includes terms related to the anisotropic interfacial energy, which is defined by the interface angle with respect to a reference angle. One of the natural numerical methods on curved surfaces is a computational technique based on a triangular mesh for the surface in a three-dimensional space. However, it is difficult to compute terms with the interface angle on a triangular mesh. To resolve this problem, we solve the governing equation in Cartesian coordinates after rotating each vertex and the 1-ring neighborhood of the vertex on the triangular mesh. After rotation and interpolation, we numerically solve the phase-field model using a standard finite difference method. We present the results of several tests to demonstrate that the proposed algorithm can recover anisotropic ice crystal growth on a spherical surface.

Benchmarking of different strategies to include anisotropy in a curvature-driven multi-phase-field model

Two benchmark problems for quantitative assessment of anisotropic curvature driving force in phase field method were developed and introduced. Both benchmarks contained an anisotropically shrinking grain in homogeneous matrix. The first benchmark was a shrinking Wulff shape and in the second, such inclination dependence of the kinetic coefficient was added so that the shrinkage was isotropic. In both cases the match to the expected shape was quantified by means of Hausdorff distance and the shrinkage rate was analytically expressed. Three different ways of interface energy anisotropy inclusion in a multi-phase field model were compared. Because their performance was comparable, they were tested in an additional benchmark problem, which concerned direct measurement of equilibrium triple junction angles. Based on this benchmark, only one of the three strategies to include anisotropy was reliable in strongly anisotropic systems.

Quantitative Phase Field Modeling of Li Dendrite Growth

Modeling and understanding dendrite growth on lithium metal anodes during charging is vital for improving battery safety. The phase field method has become an increasingly popular tool to achieve this due to its flexibility in handling complex morphologies and coupled physical processes. However, quantitative phase field models under realistic electrochemical conditions are rare. In this work, we derive a thermodynamically consistent phase field model in the grand potential framework. The design of this model emphasizes quantitative modeling of electrodeposition with experimental loading conditions and realistic length and time scales. First, electrostatic potentials in both the electrode and the electrolyte are considered to account for the interfacial potential difference. Second, the electrochemical driving force can be large even with an applied voltage of a few hundred millivolts; therefore, the grid size usually must be as small as a few nanometers to maintain a stable phase field profile. This hinders the modeling of system sizes of practical interest. To solve this problem, a mapping approach is introduced to maintain stability with moderate grid sizes and realistic applied voltages. Third, we thoroughly compare the phase field model with results from a sharp interface model for various cases that permit analytical solutions. Numerical studies demonstrate that the proposed model can quantitatively reproduce the sharp interface results. Moreover, lithium has highly anisotropic interfacial energy, which leads to corners on the equilibrium electrode-electrolyte interface shape. A convexification method is used to remove the ill-posedness due to this strong anisotropy. Finally, a parallel solver is developed to handle large systems. The overall framework is demonstrated by studying lithium dendrite morphologies under various conditions. In future work, the model can be used as a computational tool for the high-throughput screening process in battery design.

An interface-oriented data-driven scheme applying into eutectic patterns evolution

Solid-liquid interface dynamics plays a crucial role in microstructure evolution during solidification. However, it is difficult to extract sufficient spatial information to describe the variation in the irregular and non-periodic solid-liquid interface domains, resulting in a challenge remaining in quantifying analysis by a quick and low-dimensionally visualized way. We proposed an interface-oriented two-point statistics method to solve the unbiassed statistics of the spatial information in these irregular and non-periodic interfaces. The challenge was successfully overcome by a carefully designed data-driven scheme, which has the advantages of easy to operate, high accuracy and efficiency. Taking the eutectic microstructure evolution simulated by phase-field method as an example, we also obtained novel insights on tailoring eutectic patterns, that is, the transformation of four patterns (lamellar elimination, regular lamellae, oscillatory eutectics and branching lamellae) depends on initial lamella spacing whether the interface energy is isotropic or anisotropic. Additionally, interfacial energy anisotropy, compared to the isotropic case, not only prolongs the time of patterns transformation, but also narrows the spacing range between elimination and creation of lamellae. Our proposed scheme is also able to be applied into more occasions about microstructure evolution in different materials systems.

Non-regular dendritic pattern selection induced by interface energy anisotropy in the directional solidification of Al-3 wt% Mg single crystals

• Finding plate-like and hyperbranched seaweed in 3D conditions of metallic alloy. • Constructing a non-regular dendritic pattern selection map. • Well understanding effect of interface energy anisotropy on the dendritic pattern. Dendritic morphology and pattern selection are fundamentally important issues in solidification cycles. Here, a well-designed experiment was employed to investigate the solid–liquid interface energy anisotropy on the directionally solidified microstructures of Al-3 wt% Mg single crystals. Various dendritic morphologies, including regular dendrite, plate-like seaweed and hyperbranched seaweed, were found along the <100>, <110> and <111> orientations, respectively. The primary dendritic arm spacing (PDAS) of the seaweed pattern is closely related to the interface energy anisotropy and deviates from the current PDAS model. A non-regular dendritic pattern selection map is constructed to interpret the different dendrites occurring in alloy solidification.