Al2O3-ZrO2 (Y2O3) eutectic ceramics are promising high-temperature structural materials with excellent thermal stability and mechanical properties. Crystallographic orientation control is effective for tuning their performance. Herein, we investigated the crystallographic orientation rotation of Al2O3 and ZrO2 phases in the rod-like and lamellar micro-regions into the core of the colonies of Al2O3-ZrO2(Y2O3) eutectic ceramics prepared by the seeding melt-grown method. Results show that ZrO2 phases exhibit diverse growth directions with gradual rotation in both regions. However, Al2O3 phases exhibit distinct rotational behaviors depending on the morphology: in lamellar regions, the crystallographic orientations of both Al2O3 and ZrO2 phases rotate synchronously, with the misorientation angle per unit length relative to an initial position reaching up to 2.09 degrees & sdot;mu m-1; in rod-like regions, the Al2O3 phase shows negligible rotational displacement. Crystallographic orientational rotation behaviors were measured in these melt-grown eutectic ceramics, providing a research basis for the solidification of oxide eutectics.

This study presents a novel approach for surface modification and fatigue life enhancement of 1420 Al-Li alloy by introducing pulse current during shot peening. The effects of conventional shot peening (CSP) and electro-pulse assisted shot peening (EASP) on fatigue life and microstructure are systematically compared. In addition, the temperature of the EASP sample during the shot peening process is predicted by establishing a comprehensive heat transfer model, revealing that the strengthening behavior is therefore attributed primarily to athermal effects in EASP sample. Notably, the EASP15 sample exhibits more pronounced grain refinement, compressive residual stress, and work hardening than its CSP counterpart. Under a stress load of 0.9 sigma ys, the fatigue life of EASP15 sample is 12 times that of the original sample, whereas CSP sample yields only a 2.16-fold increase. The introduction of pulse current enhances peening effectiveness by increasing the surface strengthening layer thickness and peak residual compressive stress, which is attributed to two competing athermal effects: softening and annealing. At low current densities, the softening effect predominates; at higher densities, however, annealing dominates, reducing the hardened layer thickness and thereby diminishing the positive impact. Collectively, these findings offer new insights into enhancing Al alloy fatigue life and provide robust support for further optimization of current parameters.

High-entropy fluorite ceramics (HEOs) of the MexRE1-xO2-u03B4 type are attracting increasing attention in high-temperature structural materials due to their excellent high-temperature stability, low thermal conductivity and unique oxygen ion conductivity. Conventional sintering (CS) of these materials typically requires temperatures exceeding 1600 u2103 and prolonged holding times, leading to high energy consumption and abnormal grain growth. Flash sintering (FS) uses electric field and Joule heating to reduce sintering temperature (u0026lt;1000 u2103) and time to minutes, lowering energy, suppressing grain coarsening, and enhancing functionality. However, the comprehensive effects of process parameters on the microstructural evolution and defect dynamics of HEOs remain insufficiently understood. This study investigates the sintering behavior and microstructural evolution of MexRE1u2212xO2u2212u03B4 ceramics under an applied electric field, revealing the densification mechanisms driven by multi-physical field coupling. The results demonstrate that under an electric field of 700 V/cm, the furnace temperature for the FS method is reduced by 561 u2103 compared to the CS method, yielding an average grain size between 1.5 and 3.0 u03BCm. With increasing electric field strength, both the onset temperature and incubation time for FS method exhibit an overall decreasing trend. Simultaneously, electron paramagnetic resonance (EPR) spectroscopy reveals a substantial increase in oxygen vacancy concentration within the ceramic matrix following the application of the electric field. Driven by the strong electric field, intense electrochemical reduction disrupts the phase stability of the HEO matrix, leading to the preferential segregation of the LaYbO3 phase. As the electric field strength further increases, the remaining rare-earth (RE) elements undergo deep solid solution into this segregated phase to form a LaREO3u2212u03B4 solid solution. This evolution ultimately triggers lattice expansion and abnormal grain growth within the HEO matrix.

This study investigates the effect of cryogenic shot peening (CSP) conditions on aluminum alloys' fatigue performance and failure characteristics. A self-made liquid nitrogen cryogenic jet peening system was used to treat 2024 aluminum alloy samples, with the shot peening temperature ranging from room temperature (25 degrees C) to-180 degrees C. Tensile-tensile fatigue testing was conducted, and the fatigue performance was analyzed on the basis of the surface integrity of the shot peened specimens. The experimental results show that CSP significantly improves the fatigue performance of aluminum alloys, with a more pronounced effect than traditional room temperature shot peening (RT-SP). The average fatigue lifes of specimens were 6.28 x 104 cycles for the untreated, 9.44 x 104 cycles for the conventional shot peening, and 17.9 x 104 cycles for the CSP. The improvement in fatigue performance is attributed to the CSP treatment, which achieves lower surface roughness, higher surface hardness, and greater residual compressive stress in the surface layer. In addition, the CSP process also induces grain refinement and optimizes grain orientation, which plays a crucial role in enhancing the fatigue performance of the aluminum alloy.

By conducting adiabatic cyclic loading tests on three types of NiTi alloys with different martensite contents, dislocation densities, and grain sizes, the intrinsic influence mechanisms of different microstructures on the superelasticity, deformation modes, and elastocaloric cooling effect during the deformation process of NiTi alloys were investigated. The results show that the presence of a high dislocation density, high martensite content, and small grain size can reduce the degree of superelastic functional degradation and the possibility of local uneven deformation in NiTi alloys. However, the elastocaloric cooling ability is weak. A smaller strain value results in superior superelasticity (minimum epsilon(residual) =0.23%), but inferior elastocaloric cooling ability (maximum triangle T-cooling=0.63 K). Completely eliminating dislocations and martensite, as well epsilon residual as increasing grain size, can achieve a significant elastocaloric cooling capacity (triangle T-cooling=25 K), but induces severe functional degradation (a drop from 25 K to 9.6 K, a decrease of 61.6%). Annealing at 400 degrees C for 15 min to tailor the dislocation density, martensite content and grain size results in good superelasticity, uniform deformation ability and a considerable elastocaloric cooling ability (triangle T-cooling=7.2 K), along with improved resistance to functional degradation.

The Cu2O layer formed during the initial corrosion of copper and copper alloys in chloride-containing environments plays a critical role in both its own stability and the subsequent deposition behavior of Cu(II) corrosion products. In a self-corrosion system, this Cu2O layer exists in a dynamic process between dissolution and deposition, with its growth exhibiting pronounced anisotropic characteristics. However, the epitaxial relationship and coalescence mechanism between the Cu2O layer and the substrate under such conditions remain to be fully elucidated. This study mainly investigates the self-corrosion behavior of high-surface-energy Cu(011) single crystals in 3.5 wt% NaCl solutions. The results reveal that the Cu2O corrosion product formed on the Cu(011) surface exhibit different epitaxial relationships with the substrate, including matrix-aligned and twin-like orientations, and the number of epitaxial variants is regulated by the surface atomic symmetry of the substrate. During the early stages of corrosion, two types of corrosion facets develop on the surface. Among them, the structurally more stable Cu(111) facets serve as favorable substrates for the oriented attachment of Cu2O nanoparticles from the solution. This oriented attachment is achieved through the coordinated action of two epitaxial modes (namely matrix-aligned and mirror-symmetric), which enable crystallographic co-alignment between the Cu2O (111)/(111) and Cu(111) facets, resulting in the formation of Cu2O crystals with two symmetric orientations. In contrast, Cu(100) single crystals, which possess higher crystallographic symmetry, lead to the deposition of Cu2O with four equivalent spatial orientations.

To address the challenges of poor formability, large springback, and low precision in the room-temperature V-bending of high-strength 2A97 Al-Li alloy, this study innovatively proposes a novel “metal matrix + rounded graphite” composite punch design for pulse current-assisted V-bending experiments. The effects of different mold structures and current paths on the temperature distribution, bending limit, forming precision, and microstructural evolution of 2A97 Al-Li alloy during forming were investigated. The results indicated that compared with room-temperature bending, the current-assisted bending process significantly reduces the bending load of 2A97 Al-Li alloy, increases the bending limit to 31° (whereas room-temperature bending results in fracture at only 115°), and improves forming precision. The “metal matrix + rounded graphite” composite punch enables precise local high-temperature control in the bending deformation zone, which enhances the plastic deformation capacity of the deformation zone and reduces the risk of cracking. Furthermore, this structure notably decreases the current density required for self-resistance heating of the alloy—only 11 A/mm² is needed to reach the target forming temperature of 400 °C, far lower than the 50 A/mm² required by traditional metal punches—and reduces the bending springback angle to 1°, corresponding to a 66

This study investigated the effects of two types of textures, {110}< 110 > and {001}< 110 > , on the anisotropy of superelasticity and elastocaloric cooling (EC) effect in NiTi alloys. Cyclic tensile tests were conducted along various deformation directions angles (theta) between the rolling direction (RD) and the transverse direction (TD). The results demonstrated that as the texture intensity weakens and the content of dislocations and stable martensite decrease, the degree of superelastic anisotropy of the samples along different deformation directions theta also diminished. In contrast, the anisotropy of the samples' EC effect remained unaffected. By calculating the theoretical transformation strains (epsilon(theo)) in different theta, it was found that for samples with an identical microstructure, the anisotropy observed in the EC effect was governed by the anisotropy of epsilon theo. On contrary, the anisotropy of superelasticity was influenced by the synergistic coupling of epsilon theo anisotropy, dislocation density, and stable martensite content.

ObjectiveFretting fatigue widely occurs in numerous engineering components and can drastically reduce their service life. Due to the complexity of fretting fatigue problems, a universal fatigue life prediction method applicable to diverse fretting fatigue loading conditions has not yet been established. It is essential to verify the applicability of the path selection method (PSM), which integrates the point approach and multiaxial fatigue criteria, for predicting the fretting fatigue life of Ti-6Al-4V under various fretting fatigue conditions.MethodsTwo sets of fretting fatigue test data of Ti-6Al-4V alloy under cylinder-on-flat and flat-on-flat contact configurations were adopted. The PSM integrated with four types of multiaxial fatigue criteria was employed to predict fretting fatigue life, and the predicted results were compared and analyzed against test data.ResultsThe results reveal that taking the path with the minimum predicted life screened by the PSM as the life prediction path of the point method is valid for fretting fatigue life prediction of Ti-6Al-4V alloy under flat-on-flat contact configuration, and can also accurately estimate fatigue life under other fretting loading conditions.

This paper proposes a systematic quantitative assessment index for in-plane and volumetric multi-directional deformation stability of a three-dimensional mechanical metamaterial with multi-directional anti-torsion and efficient energy absorption characteristics. It establishes the correlation between deformation behavior and macroscopic mechanical properties. In two-dimensional plane, there are three distinct laying methods: zerospacing staggered interlocking arrangement, fixed-spacing staggered interlocking arrangement, and parallel arrangement. Additionally, the two-dimensional plane is arranged through cross intersections, extending into a three-dimensional reentrant star-shaped hybrid honeycomb structure (3D-RSH). To validate its performance, systematic finite element simulations and quasi-static in-plane compression tests are carried out. The results indicate that the introduction of inter-column spacing during the compression process can induce a non-central symmetric rotational deformation pattern at the upper and lower ends, which simultaneously enhances the structure's concave effect under horizontal loads along the YZ and YX planes, whereas the parallel array assembly method exhibits the best multi-axial overall deformation stability. Parametric analysis further reveals that relative density, geometric feature parameters and structural configurations all significantly influence the mechanical performance of the structure. The specific stiffness increases monotonically with relative density. When the relative density is in the range of 0.07-0.09, the negative Poisson's ratio effect is enhanced as the density increases. Under vertical loading conditions, the unit weight energy absorption of the zero-spacing staggered interlocking arrangement configuration increased by 10.6% to 31.9% compared to other configurations; while under horizontal loading, the parallel array (PAT) configuration exhibits the best energy absorption performance. Under a compaction strain of 0.5, the specific energy absorption of the fixed-spacing staggered interlocking arrangement structure increased by 11.7% compared to the zero-spacing staggered interlocking arrangement configuration, rising to 32.3% after compaction. All three arrangement methods demonstrate relatively weak energy absorption capabilities at low angles (approximately 20 degrees ), however, when the angle theta 1 reaches the threshold of 25 degrees , the overall torsional tendency of the structure significantly increases.

Electrolyte wetting is one of the core technical challenges in the development of high-performance lithium-ion batteries. It is difficult to optimize and accurately monitor the electrolyte wetting process using existing technologies. To address these issues, this study characterizes the key parameters of lithium-ion battery materials and establishes a homogenized model for electrolyte wetting based on the COMSOL Multiphysics coupling simulation platform. The model can predict and analyze the time-dependent variation of the wetting degree and evaluate the influence mechanisms of various parameters on the wetting process. Wetting experiments were conducted, verifying that the established model can predict the wetting process in porous media to a certain extent. The results show that the pore structure of porous media, temperature, pressure, contact angle, and surface tension all significantly affect the electrolyte wetting process in lithium-ion batteries. These findings provide an important theoretical basis for optimizing the manufacturing process of lithium-ion batteries.

The microstructural evolution and mechanical properties of near-alpha TA16 titanium alloy under electrically assisted (EA) tension and high-temperature (HT) matched tension conditions were systematically investigated. The results show that the flow stress of the TA16 titanium alloy decreased with the increase of the temperature. At the same temperature, the flow stress of the EA specimen is consistently lower than that of the HT specimen. In particular, at 450 degrees C, the ultimate tensile strength of the EA specimen is only 63.2% of that of its HT specimen. Microstructural observations reveal that the pulsed current facilitates dislocation slip and annihilation, mitigates dislocation accumulation, and promotes the formation of dynamic recrystallization (DRX) grains. The fraction of recrystallized grains increases markably from 0.9% at 250 degrees C to 26.6% at 450 degrees C. Moreover, the continuous dynamic recrystallization (CDRX) via the progressive coalescence and rotation of sub-grains and discontinuous dynamic recrystallization (DDRX) through grain boundary bulging could be observed.

This paper presents a type of mechanical metamaterials with a high multiaxial stable deformation energy density, balancing conflicting mechanical properties such as high stiffness, large deformation, negative poisson's ratio behavior, and multiaxial stability. A re-entrant-star hybrid structure (RSH) is designed by embedding star-shaped unit cells within inward unit cells to achieve structural integration. Finite element simulations and quasi-static in-plane compression experiments are conducted for comparative validation. The results indicate that the RSH-1 structure primarily exhibits 'X'-shaped deformation and bending with overall rotation in the diamond deformation band during compression. Based on the deformation modes of representative unit cells, a theoretical model for the stress of the RSH-1 platform is established, showing a good agreement with numerical results, with an error of approximately 9%. Parameter analysis reveals that the type of unit cell deformation mechanism and the uniformity of density significantly affect the specific energy absorption. A larger angle of the theta 1 and a higher overlap ratio can enhance the NPR effect. Under the premise of the mutual restriction between the specific energy absorption and stability, the energy absorption performance of the RSH-a structure, which shows a significant improvement, is approximately 456% and 469% higher in the x and y directions, respectively, compared to the best-performing antichiral structure configuration in the base structure. The stability of the RSH-b structure, which significantly enhances stability, shows a 13.8% decrease in y-direction stability compared to the star-shaped configuration, while in the x direction, it improves by 88.3% compared to the inward configuration.

To achieve reliable joining of (Zr,Hf)B2-(Zr,Hf)O2 ceramics with Nb521 superalloy, vacuum brazing experiments were conducted using FeCoCrNiCu0.5Mox high-entropy alloys (denoted as xMo, where x = 0, 0.5, 1) as fillers. This study investigates the effect of Mo content on the microstructure and mechanical properties of the joints, clarifying the formation mechanism and failure behavior of ZBHO20/xMo/Nb521 joints. The results indicate that the mechanical properties of the joints improve with increasing Mo content in the filler. Notably, the shear strength of the ZBHO20/1Mo/Nb521 joint reaches 365.87±20.4 MPa, which is 263.15% higher than that of the ZBHO20/0Mo/Nb521 joint (100.75±10.1 MPa). The good mechanical properties of the ZBHO20/1Mo/Nb521 joint can be attributed to the well-bonded boride reaction layer of the ZBHO20 ceramic side, as well as the coherent FCC/μ3 composite structure with a low misfit (2.5%) formed in the center of the joint. This combined soft-hard phase composite structure provides good load-bearing capacity for the central region of the joint.

Mo and its alloys exhibit considerable potential for aerospace high-temperature components, electronic thermal management systems, and high-temperature power-generation structures due to their high melting point, excellent elevated-temperature mechanical strength, and good creep resistance. However, their application is severely limited by rapid oxidation at temperatures above 700 C-o, where the formation and volatilization of MoO3 lead to accelerated material loss and structural degradation. This oxidation susceptibility can ultimately result in disintegration and catastrophic failure under extreme service conditions. The application of silicide-based coatings is an effective strategy to mitigate high-temperature oxidation by forming a protective barrier that isolates the substrate from the environment. Nevertheless, monolithic silicide coatings often suffer from premature failure caused by thermal expansion mismatch with the substrate and inward silicon diffusion during prolonged high-temperature exposure. In this context, silicide-boride composite coatings have emerged as a promising alternative for further improving oxidation resistance. Despite their potential, the mechanisms governing gradient microstructure formation and the origins of performance variability in such composite coatings remain insufficiently understood. In this study, silicide and silicide-boride composite coatings were fabricated on pure Mo substrates using halide-activated pack cementation, and their microstructural evolution and high-temperature oxidation behavior were systematically investigated. The results demonstrate that B element incorporation promotes the formation of a silicide-boride composite coating with a five-layer graded structure: MoSi2 /(MoSi2 + MoB)/Mo5Si3/MoB/Mo2B. Notably, B facilitates the preferential formation of an initial MoB interlayer at the coating-substrate interface. This interlayer not only inhibits the directional diffusion of Si but also induces a displacement reaction between Si and MoB to form MoSi2 , thereby suppressing the (001) preferred growth orientation of MoSi2 . In addition, volume contraction associated with MoB formation within the MoSi2 + MoB mixed layer generates pores and a roughened interface, which act as high-density nucleation sites and significantly refine the surface MoSi2 grain structure. The refined grain structure accelerated the formation of a dense and continuous SiO2 protective film, thereby effectively inhibiting O diffusion. After 30 h of oxidation at 1200 C-o, the silicide-boride composite coating exhibited an oxidation mass gain of 1.28 mg/cm(2) and an oxidation rate constant of 0.29 mg/(cm(2)& centerdot; h), representing a 53% reduction relative to the silicide coating. Moreover, the MoB interlayer suppressed inward Si diffusion into the substrate, thereby enhancing long-term stability under high-temperature oxidative conditions.

Defect fluorite high-entropy ceramics are potential candidates for thermal barrier applications due to their potential for efficient preparation, uniform elemental distribution, and structural stability. In this study, highentropy oxide (HEO) nano-powders with a single-phase composition were synthesized via sol-gel reactions using HPMA and metal salts, followed by heat treatment at 600 degrees C. Dense ceramic bulks with homogeneous microstructure and elemental distribution were subsequently obtained via ultrafast high-temperature sintering (UHS) methods at 1600 degrees C. Under rapid heating, the formation of non-equilibrium grain boundaries limits grain boundary relaxation and maintains a higher diffusivity state, allowing the UHS method to achieve full densification more rapidly than the CS method, thereby avoiding the extensive grain growth typically associated with prolonged isothermal holding. In addition, the HEOs demonstrated excellent thermal shock resistance, with negligible degradation in mechanical properties after 30 cycles. These findings demonstrate that the synergy between the sol-gel method and UHS enables rapid and effective sintering of defect fluorite ceramics for hightemperature applications.

A novel current-assisted heat treatment die with “metal body + rounded graphite” structure was proposed to suppress the bending springback of TA15 titanium alloy. Results indicate that the die of metal–graphite rounded corner die with 316L lower die (Die #2) achieves targeted heating at 680 ℃, reducing the springback angle from 4° to 0.2° and basically eliminating springback. The thermo-electric coupling effect promotes stress relaxation and static recovery, decreasing dislocation density and residual stress significantly. Theoretical calculations indicate that dislocation motion acceleration is primarily governed by the local hot spot effect, with the electron wind effect negligible upon ignoring thermal conduction and other heat losses. This work provides a high-efficiency and low-energy method for precision bending of TA15 alloy.

In recent years, ZrB2, as a representative material of ultra-high temperature ceramics (UHTCs), has become an important candidate material system for components of new generation aerospace vehicles. However, its practical application is limited by difficulties in material preparation and processing of complex components. This study aims to optimize sintering process of ZrB2-based UHTCs by introducing HfSi2 as a sintering aid, specifically addressing the challenge of densification caused by low intrinsic diffusion coefficient of traditional ZrB2 ceramics. The research focuses on elucidating formation mechanism of core-rim structured borides and their role in enhancing densification of ZrB2-HfSi2 ceramics. Dense ZrB2-HfSi2 ceramics were successfully fabricated via hot-press sintering at 1600 degrees C. The results reveal that softening of HfSi2 phase during sintering effectively fills interparticle gaps, thereby facilitating low-temperature densification. Furthermore, during the holding stage, interdiffusion of Hf and Zr atoms through a dissolution-reprecipitation mechanism facilitates formation of a core-rim structured ZrB2/(Zr,Hf)B2 composite. This core-rim structure consists of ZrB2 core encased by a (Zr,Hf)B2 rim, characterized by a fully coherent interface (hexagonal P6/mmm symmetry) with a low lattice mismatch (<5%), ensuring interfacial stability. The ZrB2-HfSi2 ceramic exhibits a compressive strength of (1333+83) MPa, a Vickers hardness of (15.86+0.72) GPa, and a fracture toughness of (2.01+0.36) MPam1/2. The ZrB2-HfSi2 ceramic demonstrates typical intergranular fracture behavior, with only a limited number of cleavage planes displaying core-rim structural features. These findings provide critical insights into low-temperature sintering of UHTCs and underscore potential of core-rim structures in advancing the preparation of high-performance ceramics.

The 2195 Al-Li alloy is widely used in the aerospace field, where using friction stir welding technology can achieve lightweight and reduced wear designs for components. Fatigue failure, as one of the main modes of damage affecting the life and reliability of structural components, is particularly significant. This paper thoroughly explores the differences in microstructure and fatigue crack propagation behavior between the advancing side and retreating side of the friction stir welded joint in different sampling directions, providing a theoretical basis for enhancing the fatigue performance of friction stir welds. Characterization of the microstructure of the samples was performed using Electron Backscatter Diffraction (EBSD) and X-Ray Diffraction (XRD), and the fatigue properties were investigated using fatigue crack propagation rate curves and crack growth rate curves. The results indicate that the longitudinal base material grains tend to a fibrous structure, while the axial base material grains are distributed in a lamellar fashion. Compared to the advancing side of weld nugget zone, the retreating side of weld nugget zone has significantly reduced grain size and texture types. The fatigue performance of the retreating side of the weld nugget zone is superior to that of the advancing side, and the circumferential welds outperform the longitudinal welds in terms of fatigue performance.

In this work, a method to enhance the superelasticity and elastocaloric cooling effect of NiTi alloy by shot peening treatment was proposed. This work investigated the influence of shot peening on the microstructure of NiTi alloy, focusing on deformation modes (uniform and non-uniform), superelasticity and elastocaloric cooling effect during stress-cycling-induced phase transformation. The results demonstrated that shot peening significantly altered the microstructure of the samples, changing it from a fully austenitic state to a “sandwich” structure. This newly formed microstructure consists of needle-like martensite near the surface, austenite in the middle layer, and plate-like martensite at the core. Furthermore, shot peening effectively mitigated non-uniform deformation during phase transformation, resulting in reduced local strain concentrations and temperature inhomogeneity. This process also minimized the degradation of superelasticity and the elastocaloric cooling effect, thereby enhancing the cyclic stability of these properties.