Segregation Tendency Research Articles

Unveiling the strengthening mechanisms of as-cast micro-alloyed CrMnFeCoNi high-entropy alloys

The strengthening effects introduced by the addition of 2 at% titanium, vanadium, and niobium, as the well-known micro-alloying elements, to the model CrMnFeCoNi high-entropy alloy (HEA) were studied in the present work. Accordingly, the microstructure, mechanical properties, and strengthening mechanisms of the as-cast CrMnFeCoNi, (CrMnFeCoNi)98Ti2, (CrMnFeCoNi)98V2, and (CrMnFeCoNi)98Nb2 HEAs were investigated by electron-backscattered diffraction (EBSD), tensile testing, differential scanning calorimetry (DSC) thermal analysis, and theoretical calculations and measurements. Depending on the nature of the added elements and their segregation tendency during solidification, different degrees of microstructural refinement were observed in the as-cast ingots. The segregation tendency of Ti was found to be more pronounced compared to that of V (as predicted by the Scheil-Gulliver model), leading to a more refined secondary dendrite arm spacing (SDAS) and grains (resulting from the growth restriction factor and constitutional undercooling). Moreover, Nb addition led to the formation of the (Cr,Fe,Ni)2(Nb) Laves phase at the last stages via the eutectic solidification. The effect of the Laves intermetallic compound (type C14) and twinning-induced plasticity (TWIP) effect on the strength-ductility synergy was discussed. Moreover, a detailed modeling of the strengthening mechanisms revealed that the grain boundary strengthening (represented by the Hall-Petch relationship) and solid solution hardening (due to the lattice distortion) were the primary contributors to the increase in yield strength of V- and Ti-containing HEAs. On the other hand, the formation of the Laves phase, besides solid solution and grain boundary strengthening mechanisms, could lead to a considerable increase in the yield strength of the Nb-containing sample; although it would deteriorate the ductility of the alloy, as also discussed based on its brittle fracture surface appearance and the presence of micro-cracks. Accordingly, the present study is applicable to the design of modified Cantor-based HEAs.

Thermal stability of Ti-Nb-Fe ternary nanocrystalline alloys related to grain boundary segregation

Reducing the grain size of metal materials to nanometer scale is an important method to improve their strength. However, nanocrystalline materials in most cases corresponds to a non-equilibrium state and have a relatively strong tendency to reduce the total grain boundary (GB) area to diminish the energy of the system, which results in significant grain coarsening even at low temperatures. This work is based on the thermodynamic model of the ternary nanocrystalline system, selected TiNbFe alloys as an interesting ternary system and explored its thermodynamic stability. The conspicuous GB segregation tendency of Fe atoms in annealed films is the decisive factor that achieves sufficient thermodynamic stability of nanocrystalline. Ti83.20Nb15.03Fe1.76, Ti79.71Nb15.43Fe4.86, Ti77.28Nb15.88Fe6.85 and Ti75.09Nb15.25Fe9.66 nanocrystalline samples showed excellent thermodynamic stability, which against grain growth up to 400 °C. The calculation of thermodynamic model indicates that Nb solute isn't a GBs segregator in the TiNb binary system, while the Nb element greatly promotes the GBs segregation of Fe atoms in the TiNbFe ternary system. These results enrich the experimental support for solute GB segregation in ternary systems and provide a new strategy for the design of Ti-based nanocrystalline metals with excellent thermal stability.

Experimental gas-fluidized bed drying study on the segregation and mixing dynamics for binary and ternary solids

Fluidized bed drying is an evolving process: The bed hydrodynamics, including the segregation and mixing tendencies, and its interplay with mass and heat transfer change in time. In this study, pseudo-2D fluidized bed experiments are performed using binary (50/50%) and ternary (33.3/33.3/33.3%) solids mixtures. A coupled particle image velocimetry infrared thermography technique provides local solids velocity and temperature fields. Furthermore, a machine learning algorithm is applied to characterize the bed segregation and mixing dynamics. Significant hydrodynamic changes and various segregation and mixing tendencies due to the evaporation of water from the porous γ-Al2O3 material were observed. A competition between size and density-based segregation and mixing dynamics resulted in changing bed configurations, which are correlated to the local solids drying behavior. Besides, it showed that drying of wider size distributions could lead to more complex efficient process operation.

Effect of basalt fiber on self-consolidating concrete with fly ash replacement

This work explores the behavior of self-compacted concrete produced with fly ash as cement supplementary material and basalt fibers. A combination of desert dune sand and finely crushed aggregates were used as fine aggregates; the dune sand served as sustainable material as it is a regional material and does not need further pre-processing before use. Further, a maximum size of 10 mm aggregate was used as coarse aggregate. Polycarboxylic ether-based superplasticizer was used at a constant dosage of 1.5% of the total cementitious materials to maintain the targeted flow value with the reduced water-to-cement ratio. The maximum replacement dosage of cement with fly ash was 40%, as most studies recommend this ratio without altering concrete behavior. Basalt-chopped fibers with different percentages ranging from 0.5% to 2% were used as an additive to the mix with the lowest strength results. Conclusions were drawn based on the interpretation and experimental assessment of the workability and strength properties of the concrete. Rheological properties results indicate an enhancement in workability could be attained with the increase of fly ash content; However, a tendency of segregation and loss of stability was observed after a certain threshold. In the meantime, basalt fibers showed an improvement in segregation resistance with loss of workability. The compressive strength results revealed that the optimal fly ash dosage was 20%, with a strength that is comparable to the control mix strength. Meanwhile, the mix with 40% of fly ash content showed a drop in strength of 18% from the control mix, which was regained after adding basalt fiber with an optimal dosage of 1% of the total binder content.

Fresh and mechanical characterization of fly ash/slag by incorporating steel fiber in self-compacted geopolymer concrete

Industrial waste management and CO2 eradication are major environmental issues. For every ton of production of OPC, one ton of carbon dioxide is produced. Creating sustainable concrete from industrial waste is vital. Geopolymer makes sustainable concrete since its binder is fly ash, not cement. This research examines the effects of steel fibers and fluid-to-binder ratio on self-compacted geopolymer concrete. The experimental investigation used steel fibers volume fractions of 0%, 0.5%, and 1% (by concrete volume) and fluid to binder ratios of 0.6, 0.7, and 0.8. When creating the alkaline activator, the ratio of Na2SiO3 to NaOH is taken as 3. Self-compacted geopolymer concrete requires a high dose of super plasticizer (6% to 7%), however this research obtained the same characteristic with just 2% super plasticizer by binder weight. Flowability, filing ability, and passing ability are used to evaluate fresh state properties, whereas compressive and split tensile tests are used to assess hardened state properties. As steel fibers content grows from 0% to 1.0%, concrete workability diminishes. After 0.5% steel fibers, compressive strength stabilizes. Increasing steel fibers dosage from 0% to 0.5% and from 0.5% to 1.0% increases tensile strength because of the steel fibers interlocking with one another. Workability is improved by increasing the alkaline solution to fly ash ratio, but compressive and tensile strength are reduced. This is due to the fact that when alkaline solution to fly ash ratio increases, concentration of fly ash decreases as the volume of alkaline solution and liquid increases. The tendency of bleeding and segregation occur at an “alkaline solution to fly ash ratio” 0.8, resulting in very low mechanical strength; however. A balance is observed in workability and mechanical property at alkaline solution to fly ash ratio of 0.6 and 0.7 for SCFRGPC.

Stabilizing nanograined Fe-Cr alloy by Si-assisted grain boundary segregation

• Si promotes GB segregation of Cr in the NG Fe-8Cr-1Si treated by SMGT and annealing. • Cr segregation increases with the decrease of grain size, which is related to high- density GND. • NG Fe-8Cr-1Si has enhanced thermal stability and hardness due to Cr segregation. • Additions attractive to solute can stabilize NG binary alloys with weak segregation tendency. Intentional solute segregation at grain boundary (GB) can effectively stabilize the nanograined alloys by reducing the excess energy and mobility of GB, but it usually works for binary alloys with sufficient GB segregation tendency. Here, we found that the segregation of Cr can be enhanced in a nanostructured Fe-8Cr alloy with insufficient GB segregation tendency through the interaction of another solute Si (1.0 wt.%). After surface mechanical grinding treatment and subsequent annealing, the nanograined Fe-8Cr-1Si is more thermally stable than the nanograined Fe-8Cr, which is mainly attributed to the Si-enhanced Cr segregation as observed by Super-X energy-dispersive X-ray spectroscopy (EDS) mapping system. With the grain refinement to nanoscale, the thermal stability is further improved due to the increase of Cr content at GBs and the precipitates formed at appropriate high temperatures. The present finding provides guidance for the development of advanced nanostructured ternary alloys.

Effect of TiB2 on mechanical and corrosion properties of Al 7075/TiB2/Gr composite prepared by stir casting

The current study examined the microstructural, mechanical, and corrosion properties of a metal matrix composite based on an aluminium alloy (AA7075). Three types of stir-cast metal matrix composites were created by reinforcing varying amounts of titanium diboride (2, 4, and 6 wt%) in the base alloy aluminium AA7075 while keeping the graphite content constant at 5 wt%. The optical microstructural features show that the alloying additions of graphite and titanium diborides have been homogeneously mixed in the matrix phase with no agglomeration. The tendency of particle segregation along the inter-dendritic region increases as titanium diboride content increases. The hardness and tensile properties of composite materials increase as the weight percentage of titanium diboride increases. Although the increase in hardness is small,the increase in tensile properties is significant and significantly greater than the base aluminium alloy AA7075. The corrosion rate of three metal matrix composite variants was determined using the weight loss method in three different corrosive solutions: aqueous (water), acidic (HCl - Concentration 0.3 N), and basic (NaOH - Concentration 0.3 N). The overall corrosion rate of all composites is significantly lower in aqueous solutions compared to acidic and basic solutions. The composite containing 4% titanium diboride has the highest corrosion rate in both acidic and basic solutions.

Innovative Seismic Strengthening Techniques to Be Used in RC Beams’ Critical Zones

The seismic performance of a structural frame system can be enhanced by strengthening the RC beams’ critical zones. In this paper is presented an experimental study on the improvement of the beam behaviour, subjected to an alternative cyclic procedure which considers the gravity loads reflecting the real demands on the beams’ critical zone. Two strengthening solutions are presented: unbounded post-tension (PT) tendon strengthening to increase resistance and limit residual deformations, and unbounded post-tensioning with jacketing of the RC beam with unidirectional fibre mat reinforced grout (UFRG) to limit compression damage, improving section confinement, thus delaying concrete crushing and buckling of longitudinal reinforcement. The original UFRG material was developed within this study, to apply as a small thickness jacketing material for strengthening RC structures. The main idea was that the steadiness provided by preplacing continuous fibre mats into the mould reduced the fibres’ segregation tendency during the high-performance grout pouring and allowed for the optimisation of their percentage and alignment, attaining a higher tensile strength. The experimental response of the tested Specimens is presented and evaluated through performance parameters that are properly discussed and adjusted to the alternative cyclic procedure. Finally, theoretical predictions are presented, and an adjustable multilinear model is proposed to estimate the strengthening solution’s response.

Influence of chemistry and structure on interfacial segregation in NbMoTaW with high-throughput atomistic simulations

Refractory multi-principal element alloys exhibiting promising mechanical properties such as excellent strength retention at elevated temperatures have been attracting increasing attention. Although their inherent chemical complexity is considered a defining feature, a challenge arises in predicting local chemical ordering, particularly in grain boundary regions with an enhanced structural disorder. In this study, we use atomistic simulations of a large group of bicrystal models to sample a wide variety of interfacial sites (grain boundary) in NbMoTaW and explore emergent trends in interfacial segregation and the underlying structural and chemical driving factors. Sampling hundreds of bicrystals along the [001] symmetric tilt axis and analyzing more than one hundred and thirty thousand grain boundary sites with a variety of local atomic environments, we uncover segregation trends in NbMoTaW. While Nb is the dominant segregant, more notable are the segregation patterns that deviate from expected behavior and mark situations where local structural and chemical driving forces lead to interesting segregation events. For example, incomplete depletion of Ta in low-angle boundaries results from chemical pinning due to favorable local compositional environments associated with chemical short-range ordering. Finally, machine learning models capturing and comparing the structural and chemical features of interfacial sites are developed to weigh their relative importance and contributions to segregation tendency, revealing a significant increase in predictive capability when including local chemical information. Overall, this work, highlighting the complex interplay between the local grain boundary structure and chemical short-range ordering, suggests tunable segregation and chemical ordering by tailoring grain boundary structure in multi-principal element alloys.

A high-entropy (Yb0.2Y0.2Lu0.2Ho0.2Er0.2)2Si2O7 environmental barrier coating prepared by atmospheric plasma-spray

A high-entropy (Yb0.2Y0.2Lu0.2Ho0.2Er0.2)2Si2O7 coating has in the present study for the first time been prepared by using an atmospheric plasma-spray. The microstructure, composition, and properties of the coating were characterized and assessed. The phase structure of this high-entropy coating was basically the same as that of the powder. Moreover, the rare earth elements were evenly distributed (on the atomic scale) and the content was close to the theoretical value. There was no tendency for elemental segregation. This coating also showed an excellent phase stability at 1300 °C, 1400 °C, and 1500 °C, and its thermal expansion coefficient was very close to those of the ceramic matrix composites. This high-entropy coating has, thus, a high potential to be used as an environmental barrier coating, and the atmospheric plasma-spray is a suitable method to use in the preparation of these high-entropy pyrosilicate coatings.

Role of the internal oxidation layer in the liquid metal embrittlement during the resistance spot welding of the Zn-coated advanced high strength steel

Advanced high strength steel (AHSS) with the Zn coating can produce high susceptibility of liquid metal embrittlement (LME) particularly when the resistance spot welding (RSW) is involved. The internal oxidation layer formed in the subsurface of AHSS is believed to be one of the most important factors to control the Zn-assisted LME susceptibility. The role of the internal oxidation layer in the formation of the LME for the resistance spot welded joint of the Zn-coated AHSS was comprehensively investigated in the present study. The results showed that increasing the dew point of the annealing atmosphere from −40 to −10 °C can successfully produce the internal oxidation layer in the subsurface of the steel. The Zn-coated AHSS without the internal oxidation layer revealed higher LME susceptibility during the RSW compared with the one with internal oxidation layer. In particular, the elements Si and O exhibit a synchronous segregation tendency, forming an internal oxidation layer in the subsurface of the steel. The internal oxidation layer together with the internal oxides distributed at the grain boundaries can decrease the penetration motivation of the liquid Zn, reducing the LME susceptibility.

Hydrogenated vacancy induced changes in thermodynamic stability and mechanical properties of Re-containing γ-Ni/γ'-Ni3Al phase interface

Re is an important alloying element to improve the high temperature performance of Ni-based single crystal superalloys, and has a segregation tendency to the γ/γ' phase interface. Hydrogen embrittlement introduced by hydrogenated vacancies (H-Vacs) severely reduces the service life of alloys. However, the formation mechanism of hydrogenated vacancy (H-Vac) and its effects on the Re-segregated γ/γ' phase interface are still unclear. In this work, the first-principles simulations are applied to clarify the formation of H-Vac and its effects on the thermodynamic stability and mechanical properties of Re-containing γ/γ' phase interface. We find that at the Re-containing γ/γ' phase interfaces, the hydrogen atom is more likely to dissolve in the first-nearest-neighbor (1st-NN) octahedral interstices of vacancy than in the 2nd-NN octahedral interstices. The Vac-containing γ/γ' phase interface can be stabilized when hydrogen atom dissolves in 1st-NN octahedral interstices to form H-Vac complex. For the Re-containing γ/γ' phase interface, the formation of the H-Vac complex does not change its preferential cleavage plane. Moreover, the fracture strength of the Re-containing γ/γ' phase interface is always higher than that of the Re-free γ/γ' phase interface. Thus, Re can enhance the interfacial fracture strength, which is also verified by the first-principles computational tensile tests.

Effect of Mo and Cr on S-Induced Intergranular Fracture in γ-Fe

S is a common corrosion medium for austenitic stainless steels. The severe intergranular fracture of austenitic stainless steels occurs in sulfur environments. In this paper, the permeation of S at different atomic positions for three symmetric tilt grain boundary types, i.e., Σ5(210), Σ5(310), and Σ9(114) have been computed using first-principles calculations. S has the strongest segregation tendency in the Σ5(210) grain boundary. A high content of S at the grain boundary indicates harm to the grain boundary. Sulfur segregation in the grain boundaries can weaken the strength of the metallic bond. When Mo and Cr are present at the Σ5(210) grain boundary, the sulfur-induced embrittlement is inhibited. With increased S concentration at the grain boundary, the coexistence of Mo and Cr can suppress the intergranular fracture of S on the grain boundary. The reason why high-Mo stainless steel has excellent sulfur-induced intergranular corrosion resistance is explained at the atomic level.

Ab Initio Study of Alloying Impact on the Stability of Cementite in Transformation‐Induced Plasticity‐Assisted Advanced Steels

Transformation‐induced plasticity (TRIP) steels from the third generation of advanced high‐strength steels (AHSS) contain Si additions to prevent the formation of carbides. Cementite (Fe3C) is a prototype among the carbides, and despite the importance of the influence of alloying elements on its stability, mechanisms by which the elements act have not been clarified so far. Herein, ab initio calculations are employed to study the impact of several alloying elements, including Al, Cr, Mg, Mn, and Si, on the stability of cementite. Partitioning energies are calculated to determine the segregation tendency of alloying elements between the phases such as ferrite, austenite, and cementite. The change in formation energy between the alloyed cementite and the pure cementite is then used to quantify the phase (de)stabilization. Therefore, both the partitioning energy and the change in formation energy must be considered together in a multiphase alloy system to make statements about the effect of alloying elements on the cementite stability are proposed. In addition, the effects of the technically most important elements Al and Si on the mechanical properties of cementite are calculated using the stress–strain method. Both the elements are found to increase the elastic stability of cementite.

Carbon induced segregation of Ni atoms in Cu-Ni alloy

We reported a novel driving force for surface segregation of CuNi alloy by using first-principles theoretical calculation. It is found that carbon atoms dissolved in the CuNi alloy are segregated to the surface with Ni atoms, leading to the formation of Ni-rich skin alloy, which is completely different from the previously reported Cu-rich skin alloy. Moreover, the well-known Van der Waals interaction between graphene and the CuNi surface does not reverse the segregation tendency of Cu-rich surface. Our study provides a novel approach to tune the surface composition of alloy catalyst and thus the catalytic activity of the bimetallic catalysts.

On the propensity of lath martensite intervariant boundaries to hydrogen absorption using molecular statics simulation

In the current study, the influence of boundary character (i.e., tilt, twist and mixed) on hydrogen absorption was, for the first time, investigated for lath martensite using molecular statics simulations. The energies of the martensitic intervariant boundaries varied widely from 306 to 1109 mJ/m2 depending on their character. The symmetric tilt and quasi-tilt boundaries revealed the lowest and highest boundary energies, respectively. This was, to some extent, reflected by distinct boundary unit structure/s and their complexity within a given intervariant boundary type. Interestingly, the intervariant boundary energy was not the main criteria to regulate the propensity of the boundary to hydrogen absorption. Rather, absorption depended on a distinct arrangement of unit structure/s within a given boundary plane, providing different interstitial sites for hydrogen. Indeed, the propensity for hydrogen atom/s was largely determined by the number of inequivalent interstitial sites, which resulted from the interaction of wide varieties of boundary unit structures. The intervariant boundary that consisted of regular arrangements of atoms with fewer boundary unit structure variety exhibited less tendency to H/H2 absorption (e.g., 60°/[111¯] symmetrical tilt boundary). On the contrary, the presence of a substantial number of diverse unit structures within the boundary plane significantly enhanced the tendency for hydrogen segregation (e.g., 51.73°/[116¯11] quasi-tilt and 10.53°/[01¯1¯] twist intervariant boundaries). The current findings provide a fundamental basis for the engineering of the intervariant boundary network within the martensitic microstructure to significantly enhance the hydrogen embrittlement resistance. This is critical for steels used in severe environments, such as hydrogen storage and pipelines for hydrogen transportation.

Learning Grain-Boundary Segregation: From First Principles to Polycrystals.

The segregation of solute atoms at grain boundaries (GBs) can strongly impact the structural and functional properties of polycrystals. Yet, due to the limited availability of simulation tools to study polycrystals at the atomistic scale (i.e., interatomic potentials), there is a minimal understanding of the variation of solute segregation tendencies across the very complex space of GB microenvironments and the large range of alloys in which it can occur. Here, we develop an algorithmic framework that can directly learn the full spectrum of segregation energies for a metal solute atom in a metal polycrystal from abinitio methods, bypassing the need for alloy interatomic potentials. This framework offers a pathway to a comprehensive catalog of GB solute segregation with quantum accuracy, for the entire alloy space. As an initial demonstration in this pursuit, we build an extensive GB segregation database for aluminum-based alloys across the periodic table, including dozens of alloys for which there are substantially no prior data.

Cluster dynamics modeling of Mn-Ni-Si precipitates coupled with radiation-induced segregation in low-Cu reactor pressure vessel steels

Formation of precipitates enhanced or induced by irradiation causes hardening and embrittlement of nuclear structural materials. Post-irradiation microstructure characterization of reactor pressure vessel (RPV) steels has shown that precipitation can be strongly associated with radiation-induced segregation (RIS) of solutes on dislocations. However, the effect of RIS on the kinetics of Mn-Ni-Si precipitation has not been quantified and coupled in previous model predictions. In this study, a new hybrid and spatially-dependent precipitation model is developed that couples cluster dynamics with RIS with transport coefficients of diffusion mediated by vacancies and interstitials. The new approach provides a unique way to account for concurrent evolution of heterogeneous cluster densities as well as solute and point defect concentration profiles. The model is applied to study the segregation of Mn, Ni, and Si on dislocations and heterogeneous nucleation of Mn-Ni-Si rich precipitates (MNSPs) in a low-Cu RPV steel. The RIS result shows that the segregation tendency is dominated by the vacancy mechanism for Mn, Ni, and Si. The coupled cluster dynamics modeling result shows that the onset of MNSP nucleation on dislocations depends strongly on RIS and occurs at the fluence of 2×1023n..m−2. The number density and mean radius can reach ∼1024m−3 and 1−2 nm at high fluence, respectively. These observations suggest that the role of RIS and heterogeneous nucleation can be significant for RPV steels under high neutron fluence. Results of simulations adopting various dose rates and dislocation densities show an increased fraction of MNSPs on dislocations at the condition of low dose rate, high dislocation density, and high fluence.

Reolojik Parametreleri Ölçülebilen Farklı C3A Oranına Sahip Hamur Karışımlarında Optimum Su Azaltıcı Katkı Dozajının ve Su Muhtevasının Belirlenmesi

C3A ratio is one of the parameters that greatly affects the rheological properties of cementitious systems. With the increase in the C3A ratio, the water reducing admixtures and/or water requirement increases to achieve the target spread. Some parameters are taken into account such as the type of rheometer, application of the method, the homogeneous preparation of the mixture and the water reducing admixture content in determining the water/cement (w/c) ratio and water reducing admixture requirement in the mixtures produced for the measurement of the rheological parameters of paste mixtures. The mixture produced should not be too solid (it may exceed the measuring capacity of the rheometer / the mixture may not be homogeneous) and excessively fluid (there may be a risk of segregation). For this reason, it is of great importance to determine the optimum water reducing admixture requirement and water/cement (w/c) ratio in mixtures where rheological measurements can be taken. In this study, optimum polycarboxylate-based water reducing admixture (PCE) dosage and w/c ratio were investigated in paste mixtures having different C3A ratios. For this purpose, CEMI 42.5R type portland cement with 4 different C3A ratios as 2%, 3%, 6% and 9% was used. A total of 80 different paste mixtures with 4 different w/c ratios (0.30, 0.32, 0.35 and 0.40) were prepared by adding PCE (0, 0.05, 0.10, 0.15 and 0.20% by weight of cement) in 5 different dosages. According to the results, it was observed that the admixture requirement and w/c ratio increased with the increase in the C3A ratio of the mixtures. On the other hand, it was determined that the segregation tendency increased with the increase of PCE dosage and w/c ratio in mixtures with low C3A ratio. As a result, the optimum PCE dosage was determined as 0%, 0.10% and 0.15% in terms of rheological parameters in paste mixtures. Also, the optimum w/c ratio was obtained between 0.32 and 0.35.

First-principles study of surface segregation in bimetallic Cu3M(1 1 1) (M = Au, Ag, and Zn) alloys in presence of adsorbed CO

Segregation on the surface of metal alloys has a great influence on their electrochemical and catalytic properties. We have used ab initio calculations based on density-functional theory to study the surface segregation phenomena of Cu3M(111) (M = Au, Ag, and Zn) alloy systems with chemisorbed CO. The calculated results show that the chemical adsorption of CO can substantially change the segregation tendency of Cu3M(111) surface. The stability of the M-segregated surface is higher than that of the non-segregated and Cu-segregated surfaces under vacuum condition, while the stability of the non-segregated surface is the highest at the CO coverage of 1/4 ML. Moreover, the analysis of the CO adsorption behavior and the surface electronic structure indicates that the surface-adsorbate binding strength directly affects the surface segregation tendency in a reactive environment. This study provides a theoretical basis for the practical application of copper-based alloys as CO2 reduction catalysts.