Metal-ceramic Composites Research Articles

In-situ preparation of porous metal-ceramic composite from secondary aluminum dross and red mud for adsorption of organic pollutant

Secondary aluminum dross (SAD) and red mud (RM) are solid waste discharged from aluminum industry. SAD contains 10–25 wt% aluminum nitride (AlN) and RM contains 20–50 wt% iron oxide. In this work, porous metal-ceramic composite was in-situ made from SAD and RM. Iron oxide was reduced into Fe2Si by AlN, and the generated nitrogen created pores. It was studied that effect of raw material and thermal treatment on pore structure and properties of the composite. Porosity, bulk density and compressive strength of composite were 65.78%, 1.03 g/cm3 and 17.77 MPa, when SAD content was 40 wt% and sintering temperature was 1450 °C. About 95.9% of malachite green in waste water was adsorbed by composite after 24 h. The composite could be recycled by magnetic separation after adsorption, attributed to the magnetic Fe2Si. This work proposed a novel idea of making recyclable porous material for adsorption of organics in waste water.

Hybrid manufacturing and mechanical properties of architected interpenetrating phase metal-ceramic and metal-metal composites

A hybrid manufacturing process for the fabrication of architected metal-ceramic and metal-metal interpenetrating phase composites (IPCs) is elaborated and employed to assess the mechanical performance of novel, advanced composite materials. In particular, aluminum-based co-continuous composites, reinforced with triply periodic minimal surface (TPMS) steel and ceramic (zirconia) phases are engineered, combining 3D-printing and investment casting techniques. The hybrid process results in excellent wettability between the ceramic-Al and steel-Al phases, characterized through Scanning Electron Microscopy (SEM) and micro-CT scanning analysis. The arising IPCs yield mechanical properties that utterly differ from the performance of the base ceramic or steel TPMS reinforcement topologies, with the ceramic-Al composites to furnish a highly ductile response and steel-Al IPCs a remarkable post-elastic stiffening performance. Ceramic-based IPCs yield a specific energy absorption (SEA) that is more than 400 times higher than the one of single-phase ceramic metamaterials, while steel-based IPCs allow for SEA values in the order of 50 J/g, values which rank among the highest ever reported for architected IPCs. A broader Ashby-type classification is provided, while the efficiency of the IPC plastification process is associated with the obtained SEA values. Moreover, experimental results are complemented by finite element analysis insights in the effect of the interpenetrating phase design on the inner stresses developed. The hybrid manufacturing process and the co-continuous composites investigated open novel pathways in the engineering of next-generation multifunctional architected IPCs for base material combinations beyond the ones here considered.

Strong and densified 3D metal-ceramic composite with strengthened layer structure by material extrusion additive manufacturing

Material extrusion (MEX) of high-filled polymers with metal or ceramic powders has showed great potential in fabricating 3D structure combined via the powder metallurgy route. However, defects between deposited layers adversely affect the final performance of 3D components. Here, we introduced a high-flow filling approach based on effective viscosity control and optimized printing strategies for preparing high-density NiFe2O4-based cermet. We investigated the influence of powder loading and filling paths on both green and sintered samples regarding density, microstructure and mechanical properties. Polyformaldehyde (POM)-based feedstocks were developed with powder loading of 62 vol% and 56 vol%. 3D cermet with high powder loading demonstrated good shape retention but contained periodic pores due to low-flow filling between adjacent filament. Cermets with high relative density were achieved using 56 vol% POM-based feedstock because of satisfactory fluidity and high-filling effect during deposition. Filling paths determined the distribution and size of the pores, with cermet based on the (45°, 135°) trace exhibiting the most uniform and dense structure. Cermets using 62 vol% feedstock showed significant differences in flexural strength depending on the filling path, much lower than those achieved with the high-flow filling approach. Finally, 3D NiFe2O4-based cermets utilizing 56 vol% feedstock demonstrated an optimal average flexural strength of 173.5 MPa, close to 178.4 MPa of conventional injection molded samples. Hence, high-qualified metal-ceramic composites can be fabricated using MEX via the high-flow filling approach, with potential applications in complex-shaped anode, cutting tools and wear-resistant parts.

Design and manufacture of near-net-shape metal-ceramic composites with gradient-layered structure and optimized damage tolerance

Optimizing the composition and structure of materials in localized regions of the materials is an effective approach to enhance the material utilization efficiency and achieve a performance-on-demand design. However, it is challenging to achieve such design owing to limitations in manufacturing technology. In this study, we devised a method involving vat photopolymerization 3D printing and magnet-assisted pressure infiltration techniques for fabricating near-net-shape customized gradient composites with Al/Al2O3 as the model system. The mechanical properties of the fabricated Al/Al2O3 composites at specific locations could be optimized by appropriately setting the thickness ratio of the metal layer to the ceramic layer, and a desirable combination of strength, toughness, and wear resistance could thereby be achieved. The fracture behavior of the composites was analyzed through in situ observation and finite element simulations. The proposed design concept and fabrication method are flexible and adaptable, and they can be easily extended to other material systems and structural models. They are expected to pave the way for the development of lightweight, strong, tough, and near-net-shape structural and functional materials.

Bio-corrosion susceptibility of surface voids and pores in microwave sintered Ti-HAp based bio-composites

Deterioration of implants caused by human blood plasma and liquid influence is termed Bio-corrosion. It is detrimental for metal-based implants to function and affects their lifespan adversely. Hybrid-microwave sintered Titanium-Hydroxyapatite-based metal-ceramic composites were studied for corrosion behaviour in Hank's Balanced Salt solution using an electrochemical test in linear polarization potential mode. The sintering induces surface voids and pores, thus its influence on corrosion for Ti-HAp sintered composite was studied. Different corrosion characteristics were determined, and the corrosion sites were analyzed using SEM-EDS. The study could lead to the development of corrosion-resistant porous bio-implants under an actual physiological body-fluid environment.

Computational extreme value statistics of strength for WC-Co composites at small specimens

The mechanical behavior of ceramic–metal (WC-Co) composites at small specimen level is subject to significant uncertainty due to the random assembly of (1) its constituent phases, (2) the crystal orientation of the WC grains, (3) the intrinsic residual stresses, and (4) the variable level of confinement of the metallic binder, within the contiguous network of much stiffer WC grains. In the existing literature, a Weibull distribution of strength is typically assumed at large specimen level. However, it is unknown whether this assumption can be carried over to small samples. Thus, the aim of this study is to shed light into the randomness in the mechanical strength of WC-Co composites, by using Monte Carlo simulations employing Latin Hypercube Sampling. The marginal distribution of the model parameters is assumed to be a grafted zero-threshold Weibull-Gaussian probability distribution, applied individually to the ceramic particles and the metallic binder using autocorrelation fields. The deterministic models are the recently calibrated microplane models M7WC and MPJ2 for the ceramic phase (WC) and the metallic matrix (Co) respectively. Test data in the form of strength histograms, gathered from literature on tensile tests conducted on nanowires of WC-Co composites, are used to calibrate the Weibull and Gaussian parameters, the grafting point locations and the autocorrelation lengths. The deterministic models M7WC and MPJ2 are assumed to be predictive in this study, as they were already calibrated in a previously published work by the authors. The finite element meshes used in the Monte Carlo simulations are generated using real tomography images, which easily captures the Gaussian part of the probability density function (pdf) without any random variables. This approach is shown to account successfully for the randomness observed in the strength of these ceramic–metal composites. Predictions are made for the strength distribution of differently sized nanowire specimens in tension.

Characterization of Yttria-Stabilized Zirconia (YSZ) following high temperature hydrogen exposures of molybdenum-YSZ composites

Molybdenum matrix ceramic-metal (cermet) composites containing 40–70 vol% yttria stabilized zirconia (YSZ) particles (as a surrogate for ceramic fuel particles) were produced via spark plasma sintering (SPS) and exposed to flowing hydrogen at high temperature (2000–2630 K). Both steady state and thermally cycled (4 cycles with intermediate cooling to room temperature) conditions were examined for a constant total hot testing time of 80 min. Due to the high hydrogen permeability in Mo at these temperatures, pronounced microstructural degradation was observed in YSZ particles located many millimeters below the sample surface. Observed changes to the YSZ particles from the hot hydrogen testing include partial matrix debonding, thermal expansion, redeposition of material, phase changes to a monoclinic phase and cracking/bubble formation on the YSZ grain boundaries. Overall, the YSZ particles exhibited acceptable tolerance to this extreme operating environment.

Применение прогрессивных окислительных процессов для деградации диклофенака в водных растворах

The photocatalytic activity of iron-containing metal-ceramic composites based on silicon nitride modified with semiconductor tantalum oxo compounds in the process of oxidative degradation of diclofenac (DCF) was investigated. The composites were synthesized by autowave combustion in nitrogen atmosphere of ferrosilicoaluminum with different additives (5, 10, 15 wt%) of metallic tantalum. The phase composition was determined by X-ray diffraction and IR-spectroscopy, and the content of elements in local surface areas was quantitatively evaluated by X-ray spectral microanalysis. The activity of composites under conditions of heterogeneous photocatalysis, combined heterogeneous photocatalysis with photo-Fenton and "Peroxone" processes under UV irradiation, catalytic ozonation under UV and visible light irradiation was studied. The combination of heterogeneous photocatalysis and "Peroxone" process is the most effective. The Langmuir-Hinshelwood scheme was applied to establish the mechanism of DCF photocatalytic degradation process.

Tunable architectures in Al/Al2O3 composites for enhanced damage tolerance using zirconium acetate-mediated ice-templating

Achieving lightweight, robust, and resilient materials is a sought-after goal, yet concurrently achieving these attributes presents a substantial challenge. A biomimetic design approach opens doors to innovative possibilities in this domain. In this paper, we use the ice-shaping properties of zirconium acetate (ZRA) to obtain Al/Al2O3 composites with tunable architectures through freeze casting and pressure infiltration. The concentration of ZRA in the initial slurry is critical in controlling the final structure of the composites. The composites’ bending strength, compressive strength, and crack-initiation fracture toughness KIc improve with increasing ZRA concentration in the initial slurry. Interestingly, the crack-extension fracture toughness KJc demonstrates an initial decrease followed by subsequent improvement. In addition, the relationship between cracking mode and structural features in the composites is elucidated to explain the underlying strengthening and toughening mechanisms. This tunable and scale-able ice-templating and manufacturing approach opens new doors for developing high-performance metal-ceramic composites.

Novel refractory high-entropy metal-ceramic composites with superior mechanical properties

A new concept of refractory high-entropy metal-ceramic composites (HEMCC) has been proposed that combines the outstanding physical properties of both high-entropy alloy (HEA) and high-entropy ceramic (HEC). As the first HEMCC system, to the best of our knowledge, TiTaNbZr-(TiTaNbZr)C, has been developed by a powder metallurgy process. The HEA and HEC phases exhibit body-centered cubic (BCC) and rock-salt B1 crystal structures, respectively, and both phases have non-equimolar chemical compositions. With the increase of the HEC phase in HEMCC, the hardness is enhanced while the density and fracture toughness are decreased. HEA50C sintered from 50 vol% HEA and 50 vol% HEC precursor powders shows a favorable combination of flexural strength (541 ± 48 MPa) and fracture toughness (6.93 ± 0.27 MPa·m1/2) at room temperature and a high compressive strength at 1300 °C (275 MPa). The optimized mechanical performance of HEMCC might be attributed to the combination of the ductile HEA and strong HEC phases, smaller grain size, and crack arrest at HEC/HEA interfaces.

Tribocorrosion of TiC-based composites incorporating Ni and Co binders in saline solutions

Metallic binders impart necessary toughness to ceramic-metal composites, yet are vulnerable to corrosion and wear. Thus far, the tribocorrosion mechanism remains little understood, obstructing the design of durable composites for ocean drilling applications. Against this backdrop, we selected the TiC-based composites encompassing the Ni and Co binders having different standard electrode potentials as model systems, and studied their tribocorrosion behaviors with the aid of microscopic characterizations and first-principles calculations. Results showed that the TiC-Ni system maintained lower corrosion current densities at the pure corrosion condition, due to the reduced tendency of galvanic corrosion. Such system also realized lower coefficient of friction (COF) and wear losses at the pure wear condition, benefiting from the reduced adhesion at the sliding interfaces as well as the improved composite fracture toughness. Under corrosion-wear interactions, however, the TiC-Co system revealed alleviated material losses, as the rapid build-up of oxide tribolayers enhanced the surface hardness and facilitated the transfer layer formation. Thus, contrary to the intuition that corrosion-resistant binders should be beneficial to the tribocorrosion resistance, the current work highlighted the binder's ability to generate surface layers that helped to resist corrosion-accelerated wear, a point that needs to be emphasized in future development of robust composite materials.

Design of smart transforming metal ceramic multilayers

Novel metal ceramic multilayer composites with the ability to phase transform into a single phase ultra-high temperature ceramic are described. These materials offer enhanced low-temperature fracture toughness and reliability without sacrificing high-temperature mechanical properties by eliminating the metal reinforcement layers upon reaching temperatures sufficient for the activation of carbon diffusion. At low temperatures, these materials are practically indefinitely stable because of the high activation energy for carbon diffusion in the carbide layers that control the phase transformation kinetics. Here, knowledge of the overall thermodynamics, i.e., carbon content, is combined with prediction of phase transformation kinetics and toughening in the limit of small-scale yielding to characterize the design space of these novel composites. It is proposed that the ability to control thermodynamic and mechanical properties of the post-transformation ceramic via selection of metal-to-ceramic layer ratios makes these novel composites an excellent alternative to current methods for reinforcement of ultra-high temperature ceramics.

High-energy continuous wave laser ablation of alumina ceramic

The development of high-energy continuous wave (CW) laser has enabled the generation of output powers ranging from 300 to 500 kW. Understanding the ablation mechanism of CW lasers at high laser fluence is crucial for the design of effective high-energy laser protection materials. We note that the particle-like impurities present in the protective coating material can induce defects on the ceramic-like target surface during high-energy CW laser ablation, which can alter the laser absorptivity and manifest a completely different ablation mechanism. Here, we systematically investigate the mechanism of high-energy CW laser ablation of alumina ceramic, with a specific focus on the roles of defect induction, energy transfer, and impact sputtering in the dynamic ablation of target. Specifically, the transient processes between high-energy CW laser and ceramic target will be investigated in terms of the evolution results of the ablation region, the microscopic characteristics of the ablated material, the high time-resolved on-line monitoring, and the multiphase hydrodynamics simulation. Finally, the transparent property of molten alumina ceramic to laser is proved to allow for penetrating damage to ceramic-metal composites.

Selective Laser Melting and Spark Plasma Sintering: A Perspective on Functional Biomaterials.

Achieving lightweight, high-strength, and biocompatible composites is a crucial objective in the field of tissue engineering. Intricate porous metallic structures, such as lattices, scaffolds, or triply periodic minimal surfaces (TPMSs), created via the selective laser melting (SLM) technique, are utilized as load-bearing matrices for filled ceramics. The primary metal alloys in this category are titanium-based Ti6Al4V and iron-based 316L, which can have either a uniform cell or a gradient structure. Well-known ceramics used in biomaterial applications include titanium dioxide (TiO2), zirconium dioxide (ZrO2), aluminum oxide (Al2O3), hydroxyapatite (HA), wollastonite (W), and tricalcium phosphate (TCP). To fill the structures fabricated by SLM, an appropriate ceramic is employed through the spark plasma sintering (SPS) method, making them suitable for in vitro or in vivo applications following minor post-processing. The combined SLM-SPS approach offers advantages, such as rapid design and prototyping, as well as assured densification and consolidation, although challenges persist in terms of large-scale structure and molding design. The individual or combined application of SLM and SPS processes can be implemented based on the specific requirements for fabricated sample size, shape complexity, densification, and mass productivity. This flexibility is a notable advantage offered by the combined processes of SLM and SPS. The present article provides an overview of metal-ceramic composites produced through SLM-SPS techniques. Mg-W-HA demonstrates promise for load-bearing biomedical applications, while Cu-TiO2-Ag exhibits potential for virucidal activities. Moreover, a functionally graded lattice (FGL) structure, either in radial or longitudinal directions, offers enhanced advantages by allowing adjustability and control over porosity, roughness, strength, and material proportions within the composite.

The Influence of Selected Laser Engraving Parameters on Surface Conditions of Hybrid Metal Matrix Composites.

Hybrid metal matrix composites (HMMCs) are a special type of material, possessing combined properties that belong to alloys and metals according to market demands. Therefore, they are used in different areas of industry and the properties of this type of material are useful in engineering applications, e.g., in aircraft engines and electrotechnical parts. The structure of the material requires a number of scientific studies to develop an appropriate processing technology. The paper presents the susceptibility of material from the HMMCs group with the EN AC-44300 (AISi12(Fe)) aluminum alloy matrix with a two-component reinforcement made of alumina particles (AP) and aluminosilicate fibers (AF) to thermal treatment with a laser beam. During this process, laser engraving of the researched material with variable beam power Pav and variable speed of the laser head vl were carried out. A metallographic analysis of the material was carried out. After laser engraving, surface structural changes of the material were determined. The properties of the surface geometric structure of processed material were also examined. Presented studies concern laser engraving on the surface of composite from the HMMC group, which was made by vacuum infiltration. Thanks to this method, it is possible both to produce shaped and precise composite castings with saturated reinforcement and to consequently minimize machining losses. Metal-ceramic composites from the HMMC group are hard-to-machine materials which create problems during machining. The aim of these studies was to develop a laser engraving technology with Al matrix composite with the addition of Al2O3 particles and aluminosilicate fibers, which constitute the reinforcement. The focus was on the selection of engraving parameters (beam power and speed of movement of the laser head). Clear examples of engraving, suitable for macro-assessment, were obtained with minimal change in the initial surface structure of the composite.

Sugar‐Based Electroless Copper Deposition on Pectin‐Coated Alumina Microparticles

AbstractA novel approach for fabricating copper‐coated alumina microparticles utilizing a pectin‐based coating subsequently followed by electroless deposition is reported. The biopolymer pectin is modified with phosphate groups covalently binding to the particle surface, while the polymer itself promotes the formation of metal centers on the surface due to the high affinity to metal cations. The sugar‐based (galactose, xylose, and glucose) electroless plating process in combination with an organic‐based treatment ensures a homogeneous metal coating method. As a benefit, precious metal activation of alumina particles and hazardous reducing agents typically employed are not required, creating a low‐cost and sustainable process. Metal plated micro particles show a uniform and homogeneous coating rendering them as ideal additives for application in metal matrix composites. These ceramic metal composites can be used in a wide range of applications where high‐strength metal components are needed.

Advances in Surface Laser Cladding Remanufacturing of Shaft Parts

This paper provides an overview of the commonly used processes and equipment for laser cladding, including pre-set powder feeding, simultaneous powder feeding, wire feeding cladding, and coaxial cladding nozzles. By comparing the above processes and related nozzles, the coating characteristics are summarized for the selection of appropriate methods and equipment in different working environments. Meanwhile, the morphology and properties of the clad layers of shaft parts processed with different process parameters (e.g. laser power, scanning speed, lap rate, powder feed rate) and the influence of the combined parameters are overviewed. The changes and mechanisms of metals, ceramics, and metal-ceramic composites in terms of hardness, wear resistance, metallurgical bonding, and microstructure are analyzed. In addition, the application of numerical simulation techniques to simulate the temperature and stress fields and to plan the melting trajectory when laser cladding processing is performed on the surface of shaft parts are reviewed. Finally, the problems in the current research on laser cladding of shaft parts are summarized and the development directions are discussed.

(Digital Presentation) Au-Mo-Fe-Ni/CeO2(Gd2O3) As Potential Fuel Electrodes for Internal CO2 Reforming of CH4 in Single SOFCs

Recycling biogas to produce syngas (H2 + CO) through Dry Reforming of Methane (DRM) has currently attract resurgent interest. Biogas consists mainly of CH4 (55-65%) and CO2 (35-45%) and is widely produced by anaerobic fermentation of biomass [1]. DRM provides a feasible solution to eliminate greenhouse gases via production of useful chemicals and hydrocarbons.Considering the DRM energy applications the produced syngas can be used as a fuel in high temperature solid oxide fuel cells (SOFCs) for electricity production or biogas can be directly fueled in the cell without the need of an external reformer (Internal Dry Reforming of Methane, IDRM), which simplifies the SOFC system and reduces the cost [2,3]. Specifically, during IDRM at temperatures higher than 800 oC, the catalytic Reverse Water Gas Shift (RWGS) reaction may run in parallel with electrocatalytic reactions, resulting in the consumption of valuable H2. In addition, carbon deposition on the electrocatalyst surface due to CH4 decomposition, which is favored at elevated temperatures (≥ 700 oC), may also occur resulting in progressive electrocatalyst deactivation [4].Ni-based ceramic-metal composites with Yttria Stabilized Zirconia (YSZ) and Gadolinia Doped Ceria (GDC) are widely used as electrocatalysts in SOFCs because of their activity and inexpensiveness. However, nickel catalyses the formation of carbon deposits from hydrocarbons and exhibits a tendency to agglomerate after prolonged operation [3,4]. The carbon tolerance and anti-sintering tendency of nickel and specifically of Ni/GDC can be enhanced, by dispersing trace amounts of transition noble (Rh, Pt, Pd, Ru, Au) or non-noble (Co, Cu, Mo, Fe) metal elements [3,5].In this study the catalytic and electro-catalytic performance, as well as the coking resistance of Au (1 and 3 wt.%), Mo (0.4 wt.%) and Fe (0.5 and 2 wt.%) modified Ni/CeO2(Gd2O3) electro-catalysts were studied as half and full electrolyte supported cells under internal CO2 reforming of CH4 in single SOFCs, at 750-900 oC. The aim was to elucidate their activity towards the consumption of CH4, CO2, the production of H2, H2O, CO and the production of carbon, as a function of temperature and the applied current density under a biogas fuel mixture of CH4/CO2=1. Additionally, the cells comprising a modified Ni/GDC fuel electrode, an 8 mol% Y2O3 stabilized ZrO2 (8YSZ) electrolyte were characterized using I-V measurements and Electrochemical Impedance Spectra (EIS) analysis in order to investigate the evolution of the ohmic and polarization resistance values as a reflection of current. Complementary physicochemical characterization includes thermo-gravimetric measurements for the catalytic dissociation of CH4 and CO2 at 800 oC. In brief, the cell with Ni/GDC was more active catalytically compared to the modified cells, but exhibited worst electrocatalytic performance. The cells with 3 wt.% Au-0.4 wt.% Mo-Ni/GDC and 3 wt.% Au-0.5 wt.% Fe-Ni/GDC fuel electrodes were moderately active catalytically, but performed better. The main degradation factor for the unmodified cell was the higher carbon formation, which increased gradually with the increased current and was reflected on higher ohmic and polarization resistance values compared to the modified cells. Acknowledgments This research has been co-financed by the European Union and Greek national funds through the operational program ‘Regional Excellence’ and the operational program ‘Competitiveness, Entrepreneurship and Innovation’, under the call “RESEARCH-CREATE-INNOVATE” (Project code: T2EΔK-00955).

Exploring the application of composite materials in ceramic design based on fuzzy numerical analysis

Abstract Compared with traditional monolithic carbide ceramics, Cu-based composite ceramics have the advantages of higher hardness, good wear resistance and oxidation resistance and are a new type of structural ceramics with wide application prospects. This paper first proposes a novel bi-directional freezing technique to construct a three-dimensional long-range ordered layer network hierarchical structure based on the pressure infiltration process. Secondly, a composite finite element model based on fuzzy numerical analysis is proposed for the vibroacoustic analysis of the periodic composite coupled system (PCSAS). Finally, thermal analysis experiments and mechanical property tests verify the effectiveness of Cu-based composites applied to ceramic matrices. The experimental results show that the toughness of Cu-based composite ceramics increases with the increase of TiC content, and the toughness increases from 2.15±0.27Mpa.m1/2 to 4.21±0.25Mpa.m1/2 compared with that of conventional monolithic carbide ceramics. The Cu-based composite ceramics designed in this paper give full play to the advantages of the high strength of ceramic particles and high toughness of metal matrix and develop an effective method to prepare structural metal-ceramic composites. This paper has developed an efficient route for preparing structural metal-ceramic composites, which can provide a reference for materials researchers to develop high-toughness composite ceramics.

Plastic deformation of Ag/MgO interface system during tensile fracture: A molecular dynamics study

Fracture experiments on layered metal-ceramic composites show that the plastic dissipation in the metal near the crack tip accounts for most of the macroscopic fracture toughness. In this work we studied the microscopic plastic deformation mechanisms of Ag/MgO interface systems using molecular dynamics (MD) method. As tensile strain increases, lattice dislocations nucleate at interface misfit dislocations and propagate in metal layer. The formation of immobile Hirth dislocations in Ag causes hardening. As the metal layer increases, the yield strength decreases and the hardening range is shortened. Large interface area increases the degree of inhomogeneity of dislocation motion and interface fracture behavior, leading to decreased interface yield strength.