A kinetic Monte Carlo simulations with model asymmetry in binary Fe-Cu alloy leading to the same microstructure are presented. A method based on thermodynamic data for calculation of interatomic potentials dependent on model asymmetry is presented and evaluated. Results show that kinetic pathways are sensitive to model asymmetry and are compared to the classical growth and coarsening theories. Experimental diffusion data is used and compared to simulation results to determine a realistic combination for simulations.
Strengthening in age-hardenable alloys is mainly achieved through nano-scale precipitates whose formation paths from the atomic-scale, solute-enriched entities are rarely analyzed and understood in a directly-verifiable way. Here, we discover a pathway for the earliest-stage precipitation in Al-Mg-Si alloys: solute clustering leading to three successive variants of FCC clusters, followed by the formation of non-FCC $GP$-$zones$. The clusters, which originally assume a spherical morphology ($C1$), evolve into elongated clusters and orient themselves on $\{111\}_{Al}$ ($C2$) and subsequently on …
One usual way to strengthen a metal is to add alloying elements and to control the size and the density of the precipitates obtained. However, precipitation in multicomponent alloys can take complex pathways depending on the relative diffusivity of solute atoms and on the relative driving forces involved. In Al-Zr-Sc alloys, atomic simulations based on first-principle calculations combined with various complementary experimental approaches working at different scales reveal a strongly inhomogeneous structure of the precipitates: owing to the much faster diffusivity of Sc compared with Zr in th…
A fundamental question in the study of ferromagnetic shap ememory alloys is the nature of magnetoelastic coupling and the extent it drives the structural transformation. This question also holds the key to developing new and optimized alloys that combine high strains at low switching field. In the present study it is shown that the reconfiguration of the micromagnetic structure is enslaved to and follows the martensitic transformation in these alloys using the NiMnGa and FePd alloy systems. This is determined by developing a new, high speed electronic method to study the temperature dependence…
The kinetic pathways resulting from the formation of coherent L12-ordered y'-precipitates in the g-matrix (f.c.c.) of Ni-7.5 Al-8.5 Cr at.% and Ni-5.2 Al-14.2 Cr at.% alloys, aged at 873 K, are investigated by atom-probe tomography (APT) over a range of aging times from 1/6 to 1024 hours; these alloys have approximately the same volume fraction of the y'-precipitate phase. Quantification of the phase decomposition within the framework of classical nucleation theory reveals that the y-matrix solid-solution solute supersaturations of both alloys provide the chemical driving force, which acts as …
A three-dimensional phase-field approach to martensitic transformations that uses reaction pathways in place of a Landau potential is introduced and applied to a model of Fe3Ni. Pathway branching involves an unbounded set of variants through duplication and rotations by the rotation point groups of the austenite and martensite phases. Path properties, including potential energy and elastic tensors, are calibrated by molecular statics. Acoustic waves are dealt with via a splitting technique between elastic and dissipative behaviors in a large-deformation framework. The sole free parameter of th…
University of California, Irvine（加州大学尔湾分校）；University of New Mexico（新墨西哥大学）；Karlsruhe Institute of Technology（卡尔斯鲁厄理工学院）；Massachusetts Institute of Technology（麻省理工学院）；University of California, San Diego（加州大学圣地亚哥分校）；Johns Hopkins University（约翰斯·霍普金斯大学）；Stony Brook University（石溪大学）；University of Arizona（亚利桑那大学）；Los Alamos National Lab（洛斯阿拉莫斯国家实验室）；University of Tennessee, Knoxville（田纳西大学诺克斯维尔分校）
High-entropy alloys (HEAs) were presumed to have a configurational entropy as high as that of an ideally mixed solid solution (SS) of multiple elements in near-equal proportions. However, enthalpic interactions inevitably render such chemically disordered SSs rare and metastable, except at very high temperatures. Here we highlight a structural feature that sets these concentrated SSs apart from traditional solvent-solute ones: the HEAs possess a wide variety of (local) chemical ordering (LCO). Our atomistic simulations employing an empirical interatomic potential for NiCoCr reveal that the LCO…
The decomposition kinetics of a solid-solution into separate phases are analyzed with an equation of motion initially developed to account for dissipative processes in quantum systems. This equation and the steepest-entropy-ascent quantum thermodynamic framework of which it is a part make it possible to track kinetic processes in systems in non-equilibrium, while retaining the framework of classical equilibrium thermodynamics. The general equation of motion is particularized for the case of the decomposition of a binary alloy, and a solution model is used to build an approximate energy eigenst…
The study of alloys using computational methods has been a difficult task due to the usually unknown stoichiometry and local atomic ordering of the different structures experimentally. In order to combat this, first-principles methods have been coupled with statistical methods such as the Cluster Expansion formalism in order to construct the energy hull diagram, which helps to determine if an alloyed structure can exist in nature. Traditionally, density functional theory (DFT) has been used in such workflows. In this work we propose to use chemically accurate many-body variational Monte Carlo …
We use broadband ferromagnetic resonance spectroscopy and x-ray diffraction to investigate the fundamental origin of perpendicular anisotropy in Co90Fe10/Ni multilayers. By careful evaluation of the spectroscopic g-factor, we determine the orbital moment along the out-of-plane and in-plane directions. For the multilayers, we find a direct relationship between the orbital moment asymmetry and the perpendicular anisotropy, consistent with the theory of Bruno [P.Bruno, Phys. Rev. B, 39, 865 (1989)]. A systematic x-ray diffraction study revealed the presence of a trigonal strain as high as 0.7 % i…
Chemical short-range order controls deformation pathways in a complex concentrated alloy
Federal University of São Carlos（圣卡洛斯联邦大学）；Uppsala University（乌普萨拉大学）；Wallenberg Initiative Materials Science for Sustainability, Uppsala University（乌普萨拉大学瓦伦堡可持续发展材料科学倡议）；Massachusetts Institute of Technology（麻省理工学院）；The University of Manchester（曼彻斯特大学）；Baylor University（贝勒大学）；AF Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson AFB（赖特-帕特森空军基地材料与制造局空军研究实验室）
The recently developed refractory multi-principle element alloy (MPEA), AlMo$_{0.5}$NbTa$_{0.5}$TiZr, shows an interesting microstructure with cuboidal precipitates of a disordered phase ($β$, bcc) coherently embedded in an ordered phase ($β'$, B2) matrix, unlike the conventional Ni-based superalloys where the ordered phase ($γ'$, L12) is the precipitate phase and the disordered phase ($γ$, fcc) is the matrix phase. It becomes critical to understand the phase transformation pathway (PTP) leading to this microstructure in order to tailor the microstructure for specific engineering applications.…
Microstructural and Mechanistic Insights into the Tension-Compression Asymmetry of Rapidly Solidified Fe-Cr Alloys: A Phase Field and Strain Gradient Plasticity Study
Crystallization represents a fundamental process engendering solidification of a material and determines its microstructure. Driven by complex phenomena at the atomic scale, its understanding for alloys still remains elusive. The present work proposes a large scale molecular dynamics simulation study of the homogeneous crystal nucleation pathways of prototypical undercooled Al-Ni binary alloys. An unsupervised topological learning analysis shows that the nucleation sets in first from a chemical ordering, followed by a bond-orientational ordering of the underlying crystal phase. Our results ind…
The kinetics of ordering and concurrent ordering and clustering is analyzed with an equation of motion initially developed to account for dissipative processes in quantum systems. A simplified energy eigenstructure, or pseudo-eigenstructure, is constructed from a static concentration wave method to describe the configuration-dependent energy for atomic ordering and clustering in a binary alloy. This pseudo-eigenstructure is used in conjunction with an equation of motion that follows steepest entropy ascent to calculate the kinetic path that leads to ordering and clustering in a series of hypot…
Reducing critical current for spin-transfer-torque-induced magnetization reversal in CPP-GMR devices: effect of low damping and enhanced spin scattering asymmetry in $Co_2FeGa_{0.5}Ge_{0.5}$ Heusler alloy
The Bi/Ag(111), Pb/Ag(111), and Sb/Ag(111) surface alloys exhibit a two-dimensional band structure with a strongly enhanced Rashba-type spin-splitting, which is in part attributed to the structural asymmetry resulting from an outward relaxation of the alloy atoms. In order to gain further insight into the spin-splitting mechanism, we have experimentally determined the outward relaxation of the alloy atoms in these surface alloys using quantitative low-energy electron diffraction (LEED). The structure plays an important role in the size of the spinsplitting as it dictates the potential landscap…
Mo-Re-W Alloys for High Temperature Applications: Phase Stability, Elasticity, and Thermal Property Insights via Multi-Cell Monte Carlo and Machine Learning
Dynamic Kinetic Evaluation Favors Compositionally Diverse Multicomponent Alloy Nanoparticles for Hydrogen Evolution
The University of Tokyo（东京大学）；National Institute for Materials Science（物质材料研究机构）；National Institute of Advanced Industrial Science and Technology（产业技术综合研究所）
Eutectic and peritectic equilibria in coherent binary alloys
Department of Materials Science and Engineering, University of Arizona（亚利桑那大学材料科学与工程系）；Graduate Interdisciplinary Program in Applied Mathematics, University of Arizona（亚利桑那大学应用数学跨学科研究生项目）
Benchmarking Chemically Scalable Machine-Learning Interatomic Potentials for Large-Scale Simulations of Multicomponent Alloys
State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences（中国科学院力学研究所非线性力学国家重点实验室）；Department of Materials Science and Engineering, Faculty of Mechanical Engineering, Delft University of Technology（代尔夫特理工大学机械工程学院材料科学与工程系）；Faculty of Engineering Technology, University of Twente（特温特大学工程技术学院）；Laboratory for multiscale mechanics and medical science, SV LAB, School of Aerospace, Xi’an Jiaotong University（西安交通大学航天学院SV多尺度力学与医学科学实验室）；College of Physical Science and Technology, Bohai University（渤海大学物理科学与技术学院）
Proximity effect facilitates the penetration of Cooper pairs that permits superconductivity in normal metal, offerring a promising approach to turn heterogeneous materials into superconducting and develop exceptional quantum phenomena. Here, we have systematically investigated proximity-induced anisotropic superconductivity in monolayer Ni-Pb binary alloy by combining scanning tunneling microscopy/ spectroscopy(STM/STS) with theoretical calculations. By means of high temperature growth, the(3root3by3root3)R30o Ni-Pb surface alloy has been fabricated on the Pb(111), where the appearance of doma…
Expert-Grounded Automatic Prompt Engineering for Extracting Lattice Constants of High-Entropy Alloys from Scientific Publications using Large Language Models
University of Virginia（弗吉尼亚大学）；Pennsylvania State University（宾夕法尼亚州立大学）
Additive manufacturing (AM), through directed energy deposition, supports planned composition changes between locations within a single component, allowing for functionally graded materials (FGMs) to be developed and fabricated. The formation of deleterious phases along a particular composition path can cause significant cracking during the AM build process that makes the composition path unviable to produce these FGMs, but it is challenging to predict which phases will be present in as-built additively manufactured parts by analyzing only equilibrium phase relations. Solute segregation during…
