The intrinsically low toughness and high brittleness of diboride ceramics are major limitations restricting their widespread application. Toughness can be enhanced through increased configurational entropy; however, the physical mechanisms underpinning this entropy-induced toughening remain poorly understood. In this study, a comprehensive approach from element screening to mechanistic elucidation and experimental validation is undertaken to address these gaps. First, a theory-guided element screening strategy is employed. Starting from dilute solid-solution models and integrating calculation of phase diagrams (CALPHAD) composition-property fitting, Ta, Nb, Mo, Hf, and V are identified for their synergistic optimization of hardness and toughness. Subsequently, the evolution of toughness with increasing configurational entropy is assessed using bulk modulus/shear modulus (B/G), fracture toughness (KIC), and related metrics. The calculations are validated against available experimental data, revealing an almost monotonic trend, with the six-component system exhibiting a KIC exceeding 5.8 MPa & centerdot;m1/2-approximately double that of the single-component counterpart. A systematic analysis of the lattice distortion and crystal orbital Hamilton population is performed for diborides containing two to six alloying elements. From a bond-strength perspective, the toughening mechanism originates from increased thermodynamic disorder, which broadens and flattens the bond-strength distribution, giving rise to a "bond-strength trap". Experimental validation is conducted on the (TiTa)B2 and (TiNb)B2 systems with pronounced bond-strength contrast, as well as the ternary (TiTaNb)B2 system. The results corroborate the predicted electronic bonding evolution, while further analysis of phonon force constants and stacking fault energies indicates that the synergy between strengthened M-B bonds and reduced dislocation slip barriers underpins the enhanced toughness.

The present study investigates the microstructure and surface friction and wear mechanisms of WC/Fe matrix composites fabricated using three-dimensional preforms under different casting positions. Through the utilization of analytical techniques, including CT, SEM, and EBSD analyses of ceramic particle distribution and microstructure, in conjunction with finite element simulations of flow and stress field variations during casting, the interfacial strengthening mechanism of WC/Fe matrix composites is examined. This finding elucidates the correlation between casting position, microstructure, and friction and wear properties. The results indicate that ceramic particles undergo partial diffusion but remain predominantly distributed on the substrate surface, achieving surface strengthening. A broad interfacial reaction zone has been observed to form between the WC ceramic particles and the substrate, with the composite reaction zone primarily composed of Fe6W6C. Outside this interface layer, dislocation slip occurs in the Fe6W6C(224 )FCC phase, generating numerous dislocations that act as pinning sites. This mechanism serves to enhance the interface stability of the composite material. A comparative analysis was conducted, which revealed that the isostatic stress generated around the preform was minimal, thereby facilitating superior interfacial bonding. Friction and wear testing revealed that specimens prepared via the middle casting exhibited shallower wear scar depths, with an average depth of 2.342 mu m.

An Al-1.2Mg-1.5Si-0.6Mn alloy was fabricated via hot extrusion at varying extrusion ratios (R = 6.4:1, 12.7:1, and 21.2:1) to investigate the influence of the extrusion ratio on microstructural evolution, recrystallization behavior, texture characteristics, and mechanical properties. Microstructural observations reveal that Mg2Si and alpha-Al(Fe,Mn)Si phases exhibit a streamlined distribution within the alpha-Al matrix. The microstructure predominantly consists of band-like dynamically recovered (DRV) subgrains, with a minor fraction of fine, equiaxed dynamically recrystallized (DRX) grains decorating the high-angle grain boundaries (HAGBs). Furthermore, strong Brass and S sheet textures, alongside (112) ED and (101) ND fiber textures, are developed. With increasing extrusion ratio, the grains progressively evolve into a banded morphology, a phenomenon intrinsically linked to the elevated deformation strain. Consequently, both hardness and strength are enhanced at higher extrusion ratios, a behavior governed predominantly by work hardening and precipitation strengthening mechanisms. The optimal mechanical properties are achieved at R = 21.2:1, with an ultimate tensile strength (UTS) of 150.23 MPa, a yield strength (YS) of 81.59 MPa, and an elongation of 16.48%. These findings elucidate the correlation between microstructural evolution and mechanical properties, providing a critical reference for optimizing industrial aluminum extrusion processes.

WC ceramic particle reinforced high chromium cast iron matrix composites exhibit excellent wear resistance, and the characteristics of the reaction zone between WC and the matrix together with the distribution of the resulting products largely govern their overall performance. In this work, WC/Fe composites composed of WC, W₂C, Fe₆W₆C, Cr₇C₃ and α-Fe were fabricated by cast infiltration through tuning the volume ratio parameter φ between the WC preform and the matrix from 50 percent to 20 percent, and the evolution of the in situ generated Fe₆W₆C phase and its influence on the friction wear failure mechanism were systematically investigated. As φ decreases, the reaction zone temperature rises and the high temperature dwell time is prolonged, which enhances the dissolution of WC and promotes the in situ formation of Fe₆W₆C with distinct morphologies, among which the fishbone like Fe₆W₆C exhibits pronounced preferred orientation together with the highest local lattice distortion. As Fe₆W₆C evolves from a short rod like to a fishbone like structure, the hardness and elastic modulus decrease slightly, yet the average hardness remains above 740.31 HV, about 70 percent higher than the matrix. The optimal performance is attained at φ = 30 percent, with a friction coefficient of 0.64 and an average wear rate of 7.5 × 10⁻⁵ mm³/(N·m), an improvement of more than 40 percent over the matrix, while the wear mechanism transitions successively from abrasive wear to stable polishing wear and finally to adhesive wear approaching that of the matrix.

Cu@Ag core-shell structures efficiently integrate the superior properties of Cu and Ag nanoparticles, while simultaneously addressing the critical limitations of poor chemical stability of Cu and high raw material cost of Ag. In this study, multidimensional Cu@Ag core-shell micronanomaterials were successfully synthesized via electroless plating method. The investigation of the relationship between the structure of Cu@Ag core-shell micronanomaterials and their performance in hydrogenation reaction demonstrates that these materials exhibit significant catalytic efficiency and excellent reusability in the catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). Notably, the Cu@Ag core-shell nanosheets (Cu@AgNSs) exhibited the highest recorded mass-normalized rate constant (5.64 × 104 min-1·g-1), which was 4.3 times and 15.7 times higher than that of Cu nanosheets (CuNSs) and Ag nanoparticles (AgNPs), respectively. Combined structural analysis and density functional theory (DFT) calculations confirmed that the catalytic performance is governed by the synergy between the intrinsic electronic effects of the Cu/Ag interface (enhancing hydrogen adsorption and electron transfer) and the synergistic effect resulting from the exposure of interface sites. The findings of this study are valuable for advancing the development of advanced low-dimensional Cu-based micronanomaterials.

In this article, a thermal-phase model for quenching medium carbon alloy steel is developed based on multi-physics field coupling simulation. The model integrates transient heat transfer, phase transformation, and hardness calculation. Combined with experimental characterization, the effects of different quenching end temperatures on the temperature field, microstructure distribution, and hardness of the sample are systematically analyzed. The results indicate that as the quenching end temperature increases, the cooling rate at the surface and central regions of the sample gradually decreases, leading to a reduction in both the martensite content and hardness. Conversely, the impact toughness and resistance to impact abrasive wear improve. When quenched at 100 degrees C, the sample surface exhibits the highest martensite content, with the maximum hardness difference between the surface and core reaching 327.87 HV, while the impact toughness is the lowest at 28 J/cm(2). At 170 degrees C, the surface microstructure consists of a mixture of bainite and martensite, with the minimum hardness difference between the surface and core being 266.14 HV. The impact toughness and resistance to impact abrasive wear reach their optimal values of 53 and 2.94 J/cm(2), respectively. By integrating simulation with experimental analysis, the dynamic evolution of the quenching process can be effectively captured, thereby revealing the influence of process parameters on microstructural evolution and overall mechanical properties.

This study systematically investigated the effects of different solution temperatures (470, 500, 530 °C) on the microstructure, mechanical properties, and corrosion behaviour of an Al-1.5Mg-1Si-0.6Mn-1.2Zn alloy in the T4 state. The results demonstrate that the solution temperature exerts a significant influence on the dissolution behaviour of the secondary phases, Mg2Si and Al(Fe,Mn)Si. At a solution temperature of 470 °C, large black Mg2Si phases were clearly visible under OM, and the highest yield strength (66 MPa) and tensile strength (169 MPa) were obtained. As the solution temperature increased, the tensile strength of the alloy first decreased and then increased. This is attributed to recrystallisation softening causing a strength drop at 500 °C, but recovery occurred at 530 °C due to enhanced strengthening from sufficient Mg2Si dissolution. The corrosion resistance of the Al-1.5Mg-1Si-0.6Mn-1.2Zn alloy first increased and then decreased with increasing solution temperature. The alloy treated at 500 °C exhibited the lowest corrosion current density and the best corrosion resistance, which is attributed to the protective corrosion product film formed on the matrix.

Cr-Mo alloy steel is widely used for wear-resistant components subjected to combined impact and abrasive loading. In this study, Cr-Mo alloy steel was water-quenched from 840, 870, 900, and 930 °C and subsequently tempered under the same condition (300 °C for 2 h) to isolate the effect of quenching temperature. The microstructure, hardness, impact toughness, impact abrasive wear behavior, and worn-surface roughness were evaluated. Endpoint EBSD analysis showed that the retained austenite fraction increased from 0.2

Silver-coated copper nanomaterials demonstrate enhanced catalytic activity in electrochemical CO2 reduction through interfacial electron transfer effects that optimize adsorption strength. However, the interfacial binding mechanism and strategies for enhancing binding strength remain unclear due to insufficient systematic studies. In this study, we systematically investigate the mechanical properties of the Cu-Ag system, encompassing both pure metals and intermetallic compounds, through comprehensive computational analysis of their elastic, hardness, anisotropy, Poissons ratio, etc. Thermodynamic calculations demonstrate the instability of both Cu3Ag and CuAg3 intermetallic phases, confirming that the interfaces in silver-coated copper nanoparticles are composed of pure Cu and Ag. Subsequent computational studies focus on low-index crystalline surfaces (100), (110), (111), (101), and (001) of pure Cu and Ag. Surface energy and work of adhesion calculations reveal that the (111) interface possesses the lowest energy, demonstrating that the Cu(111)/Ag(111) interface constitutes the most stable interfacial configuration. Substitution of a single Si atom at the interfacial site was found to enhance the interfacial strength. Density of states (DOS) and charge density difference analyses reveal significant charge transfer at the Cu/Ag interface, with reduced charge accumulation correlating to increased tensile strength. This study provides fundamental insights into the interfacial characteristics of silver-coated copper materials, offering guidance for designing high-performance catalytic systems.

This study investigated the effects of different cooling media—air, water, and oil—on the microstructure and mechanical properties of Cr–Mo alloy steel. After austenitizing in a resistance furnace at a specified temperature for one hour, the Cr–Mo steel specimens were cooled using the respective media. Microstructural characterization was performed using scanning electron microscopy (SEM), X-ray diffraction (XRD), and electron backscatter diffraction (EBSD). Mechanical and wear properties were evaluated using a Vickers hardness tester, an impact testing machine, and an impact abrasive wear tester. The results indicate that water cooling produced a lath martensite structure, resulting in high hardness (590.6 HV), which was approximately 93

Although ZrB2-SiC (ZS) ceramics have been extensively researched for reusable space vehicles, the gaseous Si-bearing oxides are actively yielded, which limits their service for ultra-high-temperature applications (>2000 degrees C). In this work, medium-entropy oxide spiral fibers (MEOsf) with a composition of Zr0.68Y0.07Ce0.2Ti0.05O2-delta (Zr-0.68) were developed to promote the generation of oxide scale. The MEOsf-ZS composites demonstrated a low ablation rate of 0.27 mu m/s when exposed to ten 60 s cycles of oxyacetylene flame at 2150 degrees C. The first-principle calculations revealed that the MEO-Zr-0.68 exhibited minimum lattice distortion in the ferroelastic tetragonal (t) phase and a highly integrated crystal orbital overlap of the Ti-O bond, which contributed the good phase stability at high temperature. The enhanced ablation resistance of MEOsf-ZS was ascribed to the outstanding t-phase stability and structural integrity of the oxide scale. The intact MEO-glassy SiO2 oxide scale formed by capillary resistance effect of spiral geometry finally retarded the active oxidation of SiC grains.

The effects of alloy elemental segregation on the Au/Ni3Al interface are systematically investigated employing density functional theory (DFT)-based first-principles calculations. Through comprehensive atomic-scale and electronic structure analyses, the mechanisms of interfacial strengthening, elemental segregation behavior, and fracture initiation are elucidated. The findings indicate that the bridge position (MT) configuration has the maximum bond strength. Si and Ge atoms are easily separated from the Au surface to the interface, while Ni and Sn solute atoms exhibit preferential segregation within the Au matrix. When the Ni is doped, the interfacial work of adhesion increased by 16.33 % compared with the undoped interface, and the bonding strength was considerably improved. Meanwhile, the changes of chemical bonding and electronic behavior during the interfacial fracture are systematically analyzed. The fracture of three interfacial stacking models occurred inside the Au bulk phase, which are caused by the breakage of Au-Au(I) bonds in the Au bulk material. This study is a guide to the strengthening, segregation of alloying elements and fracture behavior between Au-based solder materials and base materials.

Multielement alloys with high strength and wear resistance are widely used in many critical applications. In this study, WC-NiCoMo multielement alloys were prepared via vacuum powder metallurgy sintering, and the effect of Ni/Co content on the microstructure, mechanical properties, and frictional wear behavior was investigated. After sintering, the alloy microstructure primarily comprised WC, W2C, Co3W3C, Ni2W4C, and Mo2C. The interplanar spacing of the W2C (0111) plane was 0.2276 nm, while that of the Co3W3C (311) plane was 0.3355 nm. First principles calculations indicated the formation of strong C-Co covalent bonds, and W-W metallic bonds at the W2C/Co3W3C interface.With an increase in Ni/Co content from 10 % to 30 %, the compressive strength and strain of the WC-NiCoMo alloys gradually increased, reaching a maximum strength of 1116 MPa and a maximum strain of 25.9 %. The frictional wear properties first improved and then declined as the Ni/Co content increased, with optimal performance observed at a friction coefficient of 0.178 and a wear rate of 0.95 x 10-5 mm3/N center dot m. The wear resistance of the WC-NiCoMo multielement alloys was attributable to their high hardness, strength, and strain across different alloy compositions.

The mechanical properties of metal matrix composites are frequently reduced due to the uneven distribution of reinforcement particles. In this article, the effects of three-dimensional preforms with different shapes on the microstructure of WC/ Iron-based configuration composites were examined, and the hardness, friction coefficient and wear properties of WC/ Iron-based configuration composites in different regions were measured. The findings reveal that the microstructure of the composites is mainly composed of WC, W2C, Fe6W6C, and M7C3 carbides. Compared with the triangular and quadrilateral configurations, the composite materials prepared by hexagonal configuration have better hardness and wear resistance, the matrix hardness is 921.7HV, the composite layer hardness is 1450.4 HV, the friction coefficient is the lowest (0.51), and the wear weight is the least (0.21 g). The temperature-time curves obtained by finite element simulation also confirm that the designed three-dimensional preform has a favorable metallurgical reaction with the matrix, especially the hexagonal configuration.

Based on finite element numerical simulation, the stress field, temperature field, and solidification behavior of WC/Fe matrix composites were predicted at casting temperatures of 1425, 1450, 1475, 1500, 1525, 1550, 1575, and 1600 °C. The results of the reach demonstrate that the temperature distribution between the preform and the matrix varies with the pouring temperature. The temperature change curve around the preform is observed to be the gentlest when the temperature reaches 1575 °C, which is not easy to produce the phenomenon of radical cooling during the solidification process. With the increase in casting temperature, the stress distribution on the surface of the preform shows the trend of increasing first and then decreasing; when the casting temperature is 1575 °C, the stress produced on the surface of the preform has a minimum value of 703.2 MPa, and the distribution is uniform. However, as the casting temperature continues to rise, the WC ceramic particles on the surface of the preform are completely reacted and dissolved. As a consequence of the elevated temperature, the temperature of the composite zone declines at a rapid rate during the solidification phase. This results in a considerable discrepancy in temperature between the composite zone and the matrix, which in turn gives rise to a pronounced surge in stress. It was experimentally verified that the WC ceramic particles in the preform and the iron matrix diffused to form a well-bonded interfacial layer during the casting process at a casting condition of 1575 °C, and the WC/Fe matrix composite was successfully prepared.

Although ZrB 2 ‒SiC (ZS) ceramics have been extensively researched for reusable space vehicles, the gaseous Si‐bearing oxides are actively yielded, which limits their service for ultra‐high‐temperature applications (>2000°C). In this work, medium‐entropy oxide spiral fibers (MEO sf ) with a composition of Zr 0.68 Y 0.07 Ce 0.2 Ti 0.05 O 2‒ δ (Zr 0.68 ) were developed to promote the generation of oxide scale. The MEO sf ‐ZS composites demonstrated a low ablation rate of 0.27 µm/s when exposed to ten 60 s cycles of oxyacetylene flame at 2150°C. The first‐principle calculations revealed that the MEO‐Zr 0.68 exhibited minimum lattice distortion in the ferroelastic tetragonal ( t ) phase and a highly integrated crystal orbital overlap of the Ti–O bond, which contributed the good phase stability at high temperature. The enhanced ablation resistance of MEO sf ‐ZS was ascribed to the outstanding t ‐phase stability and structural integrity of the oxide scale. The intact MEO‐glassy SiO 2 oxide scale formed by capillary resistance effect of spiral geometry finally retarded the active oxidation of SiC grains.

Vanadium carbides (VC1-x) exhibit stoichiometric flexibility due to the presence of various carbon vacancies, which significantly influence their fundamental physical properties. Despite this, a comprehensive understanding of how carbon vacancies affect the mechanical and thermal properties of vanadium carbides remains elusive. Previous research has primarily focused on stoichiometric VC and has yet to fully explore the impact of carbon vacancies. This study reveals that stoichiometric VC is less stable when compared to ordered substoichiometric VC1-x and employs first-principles calculations to obtain thermodynamic, mechanical, and transport properties of VC1-x. The ordered carbon vacancy leads to an increase in the V–V bond density and volume. Due to the anharmonic effect, the ordered carbon vacancy impairs heat capacity and thermal expansion. The hardness and toughness decrease with increasing carbon vacancy concentrations. The Boltzmann transport equation is used to calculate electrical and thermal transport properties, which shows that growing scattering effects reduce thermal transport capacity. The results provide accurate data support for vanadium carbide research and theoretical support for designing ultra-high temperature ceramic materials.

As an important strengthening phase in Al-Ca eutectic alloy, the mechanical properties of Al4Ca phase are important for its engineering application. The effects of Cu, Zn, Mg, Fe and Mn doping on mechanical properties and electronic structures of Al4Ca phase are investigated in detail based on DFT calculations. The negative mixing enthalpy and cohesive energy of all Al4(Ca,m) phases show that the substitution of Ca by m (m = Cu, Zn, Mg, Fe and Mn) is energetically favorable at 0 K. The modulus and hardness values of Al4(Ca,m) are improved from 43.3, 2.73 GPa to 47.4, 2.99 GPa, 52.3, 3.3 GPa, and 70.6, 4.45 GPa by Mg, Fe and Mn doping, while they are decreased to 35.1, 38.2 and 2.21, 2.4 GPa by Cu and Zn doping. Based on Pugh ratio (B/G, 1.75) and Poisson’s ratio (σ, 0.26) criteria, all Al4(Ca,m) phases are ascertained as ductile materials. Cu and Zn can increase the ductility of Al4Ca and the situation is in contrary after doping of Mg, Fe and Mn. Mn is the ideal element for increasing fracture toughness and decreasing the mechanical anisotropy of Al4Ca among these elements from calculation results. The calculated electronic structures show that the mechanical properties evolution of Al4(Ca,m) phases are primarily attribute to the variation of Al-m bonds.

Magnesium (Mg) alloys are widely used in automobile, rail transit, and other fields; however their heat resistance and deformation ability should be improved. In the present work, the structural characteristics, dynamic sta-bility, mechanical anisotropic, electronic structure, and thermal properties of Mg-Yttrium (Y) binary compounds are systematically explored using the first-principles calculations combined with the quasi-harmonic approxi-mation. The current calculated first-principles results reveal that MgY, Mg2Y, and Mg24Y5 are confirmed the dynamically and thermodynamically stable phases at 0 K by the phonon dispersions with no imaginary frequency and formation enthalpy convex hull graph. The calculated mechanical properties of Mg-Y compounds are gradually increased with the increase of Y content, and MgY has the largest elastic moduli, including bulk, shear, and Young's modulus, as the values with 43.82, 26.7, and 66.63 GPa, respectively. The elastic anisotropies of the Mg-Y system are illustrated by elastic anisotropy indexes and three-dimensional surface constructions, and these results show that the sequence of elastic anisotropy are MgY > Mg2Y > Mg24Y5. Additionally, the MgY phase exhibits superior heat resistance compared to the Mg2Y and Mg24Y5 phases, which is beneficial to enhance the heat resistance of Mg alloys.