Search Results (261)

Metal matrix composites (MMCs) are engineered multiphase materials in which a continuous metallic matrix contains deliberately introduced reinforcing phases. Their properties arise from the combined effects of the matrix, reinforcement, interface, processing route and spatial architecture. The matrix provides metallic continuity, plastic deformation capacity, processability and thermal or electrical conduction, whereas the reinforcement is selected to modify stiffness, strength, hardness, wear resistance, thermal stability, corrosion response or functional behavior. From a practical interpretation standpoint, MMC performance should not be ascribed solely to the reinforcement fraction, but rather to the coupled effects of reinforcement distribution, interfacial bonding, porosity, residual stress, heat-treatment state, and architecture. Full article

This study examines the effects of laser power (P), scanning speed (SS), and energy density (ED) on the microstructure and hardness of WC-reinforced Inconel 625 metallic matrix composite (MMC) coatings fabricated via a powder-based directed energy deposition (DED) process developed by Makino Asia Pte Ltd. Coating layers were evaluated for surface roughness (Sa), layer height (LH), porosity (Pr), dilution height (DH), dilution ratio (DR), and WC retention (WC%). Trends in the data reveal how process parameters influence deposition quality and microstructural evolution: higher P or lower SS increased melt pool depth, promoted WC dissolution, and coarsened microstructure, whereas lower P or higher SS preserved WC particles and minimized substrate dilution. Hardness variations in the Inconel 625 matrix were associated with dendrite size, solid-solution strengthening, dislocation density, and secondary carbide formation. These findings provide quantitative guidance for selecting DED parameters to produce crack-free WC-Inconel 625 MMC coatings with controlled microstructure and tailored mechanical properties. Full article

Boron carbide (B₄C)-reinforced metal matrix composites (MMCs) are promising candidates for biomedical implants due to their mechanical properties and potential biological compatibility. In this study, in vitro biocompatibility and cytotoxicity of B₄C-reinforced CoCrMo, Ti, and 17-4 PH alloys were systematically evaluated using human osteoblast (HOB) cells. Composites were fabricated via powder metallurgy with varying B₄C reinforcement ratios (CoCrMo and Ti: 5–10 wt%; 17-4 PH: 3–12 wt%). Extracts prepared according to ISO 10993-12 standards were applied at different concentrations (100%, 50%, 25%, 12.5%) to assess cell viability using the MTT assay over 24, 48, and 72 h. Results demonstrated a clear dose-dependent cytotoxic effect across all composite systems. Ti composites exhibited the highest biocompatibility, with cell viability largely preserved even at higher B₄C ratios. CoCrMo composites showed moderate cytotoxicity, which decreased upon extract dilution, indicating low-concentration compatibility. In contrast, 17-4 PH composites revealed significant cytotoxicity at higher extract concentrations, exacerbated by increasing B₄C content. Literature-supported findings confirm that B₄C incorporation enhances hardness, wear resistance, and elastic modulus, yet excessive reinforcement can induce local stress and particle detachment, affecting cellular tolerance. Diluted extracts of Ti and CoCrMo composites maintained cell viability at a biocompatible level consistent with ISO 10993-5 criteria. These results highlight the promising biocompatibility of B₄C-reinforced Ti and CoCrMo alloys for biomedical applications and provide a biological basis for the design of next-generation composite implants. Full article

Metal packaging materials remain fundamental across food, beverage, pharmaceutical, cosmetic, and technical sectors owing to their combination of mechanical robustness, total light and gas barrier performance, thermal resistance, and established recyclability. Aluminum alloys, tinplate, tin-free steel (TFS/ECCS), stainless steels, metal–matrix composites (MMCs), and metal–polymer or metal–paper laminates define distinct metal-based packaging architectures whose metallurgical and interfacial design governs forming behaviour, corrosion and migration pathways, coating integrity, and mechanical reliability. In this review, these architectures are examined from a materials- and systems-oriented perspective, linking composition, microstructure, processing routes, and surface engineering to functional performance across rigid, semi-rigid, and flexible formats. The analysis also considers the ongoing transition from bisphenol A (BPA)-based epoxy linings to BPA-free and hybrid coating chemistries, the use of nano-structured metallic and metal-oxide surfaces, and the role of composite laminates in which thin metallic foils are combined with polymeric or paper-based structural layers. These material and architectural aspects are discussed together with safety, regulatory, and circularity considerations that increasingly influence the design and selection of metal-based packaging. Ion migration, coating degradation, and corrosion under realistic storage environments are considered in relation to EU, FDA, ISO, and sector-specific requirements, while attention is also paid to the contrast between well-established closed-loop recycling infrastructures for aluminum and steel and the more complex end-of-life management of coated metals and multilayer laminates. The review provides a unified framework connecting materials selection, metallurgical design, processing, performance, regulatory compliance, and sustainability in metal-based packaging systems. Applications spanning consumer goods, pharmaceuticals, cosmetics, and advanced electronics are integrated to support an overall understanding of how metallic and hybrid metal-based architectures underpin functional reliability and life-cycle sustainability. Full article

The design and fabrication of metal matrix materials (MMCs), as well as the densification and joining of ceramic matrix composites (CMC), are still very challenging. For SiC- and C-based composites, liquid-assisted processing routes, such as the spontaneous infiltration process, emerge among the most cost-effective processes. To succeed in Ir-Si/SiC refractory composite fabrication by spontaneous infiltration, the wetting characteristics of the Ir-Si/SiC system, the surface and transport properties (surface tension and viscosity) of liquid Ir-Si alloys, and microstructural evolution at the interfaces formed between solid SiC (or C) with Ir-Si melt, have been carefully examined. Specifically, the wettability and interaction phenomena occurring at the Si-Ir eutectics/SiC interface as a function of temperature were investigated in the temperature range of T = 1350–1400 °C by the sessile drop method under an inert atmosphere with reduced oxygen content, and the results are presented and discussed in this paper. Taking into account the thermodynamics of the Si-C-Ir system, the interfacial phenomena and subsequent microstructural evolution are well-related to the process parameters, and the properties and characteristics of the as-produced interfaces may be predicted accordingly. The experimental conditions and results of wetting experiments, together with thermodynamic-based models predicting thermophysical property values of liquid Ir-Si alloys, are valuable key input data that are now available for the numerical study of infiltration processes. Full article

In critical sectors such as energy, transportation, and high-end manufacturing, components must endure simultaneous exposure to high temperatures, heavy loads, and severe wear, necessitating materials with balanced strength, toughness, and durability. Metal matrix composites (MMCs), enhanced with ceramic reinforcements, offer a promising solution to these multifaceted demands. While conventional techniques like casting and powder metallurgy often struggle with limited design freedom and uniform reinforcement distribution, additive manufacturing (AM) enables the production of complex, graded components with tailored microstructures and unlocks new possibilities for materials operating under extreme service conditions. This review systematically examines recent advances in AM-processed MMCs—focusing on aluminum-, titanium-, nickel-, and steel-based systems—for applications in coupled extreme environments. It provides a detailed analysis of their high-temperature mechanical performance and wear resistance, emphasizing the roles of reinforcement selection, microstructural design, and AM processing parameters in governing key properties. Furthermore, the underlying strengthening and wear mechanisms are discussed, along with current challenges and future opportunities. This work aims to serve as a foundational reference for the development of next-generation AM MMCs tailored for high-performance engineering applications. Full article

Metal matrix composites (MMCs) are one of the significant engineering materials for many industrial applications. The growing interest in MMCs stems from their strong mechanical properties, including their higher specific mechanical strength and excellent corrosion and wear resistance. From an industrial viewpoint, the ability of MMCs to undergo secondary processing is significant. This review aims to clarify the effects of cryorolling on the microstructure, mechanical properties and wear behavior of different aluminum-based MMCs. In particular, aluminum matrix composites (AMCs) produced through the stir-casting approach experience an additional cryorolling procedure to enhance their tensile mechanical strength and wear resistance. This hybrid manufacturing approach has shown promise in creating effective structural components. This review covers the production of ex situ aluminum-based composites formed by stir casting and then cryorolling. It also highlights how the particle size, volume fraction, and the cryorolling procedure affect the microstructure, wear, and mechanical properties. This approach could broaden the uses of hybrid manufacturing by demonstrating its practical advantages and efficiency. Furthermore, this review highlights the importance of implementing machine learning (ML) models and life cycle assessment (LCA) in evaluating MMCs produced through stir casting. Full article

This study evaluates the performance of a copper-based metal matrix composite (Cu-MMC) brake pad fabricated by powder metallurgy for high-speed railway braking applications. The material was produced via homogeneous powder mixing, compaction at 650 MPa, and sintering at 950 °C for 2 h to promote densification and metallurgical bonding. The fabricated Cu-MMC exhibited densities of 5.71–5.98 g/cm³, porosities of 5.85–10.1%, and hardness values of 62–73 HV, indicating effective microstructural control. Tribological performance was assessed using a brake dynamometer at an equivalent speed of 160 km/h and a contact pressure of 0.95 MPa. The composite demonstrated a low specific wear rate of 0.11–0.14 cm³/MJ, meeting the TJ/CL 307-2014 standard for high-energy braking. Surface analysis revealed stable frictional behavior dominated by oxidative–abrasive, adhesive, and delamination wear mechanisms. Thermal evaluation showed a maximum operating temperature of 225–235 °C, below the softening temperature of copper, confirming adequate thermal stability. Full article

This study investigates the microstructural evolution and wear behaviour of aluminium 7075-based metal matrix composites (MMCs) reinforced with high-entropy alloy (HEA) particles and fabricated via friction stir processing (FSP). A detailed characterisation of the grain refinement in the 7075 matrix was conducted, revealing significant dynamic recrystallization and grain size reduction induced by the severe plastic deformation inherent to FSP. The interaction between the matrix and HEA particles was analysed, showing strong interfacial bonding, which was further influenced by post-processing heat treatments. These microstructural modifications were correlated with the wear performance of the composites, demonstrating enhanced resistance due to the synergistic effect of precipitates and particle reinforcement. The findings highlight the potential of FSP as a viable route for tailoring surface properties in advanced MMCs for demanding tribological applications. Full article

Friction Stir Processing (FSP) has emerged as an advanced solid-state surface engineering technique for tailoring high-performance surface architectures in metal matrix composites (MMCs). By combining localized thermo-mechanical deformation with controlled material flow, FSP enables grain refinement, homogeneous dispersion of reinforcement, and strong interfacial bonding without melting or altering bulk properties. This review critically examines the role of FSP in enhancing the mechanical, tribological, and corrosion performance of composites, with emphasis on process–structure–property relationships. Key strengthening mechanisms, including grain boundary strengthening, load transfer, particle pinning, and defect elimination, are systematically discussed, along with their implications for wear resistance, fatigue life, and durability. Special attention is given to corrosion and tribo-corrosion behavior, highlighting electrochemical mechanisms such as micro-galvanic interactions, passive film stability, and interfacial chemistry. Furthermore, the eco-efficiency, industrial viability, and sustainability advantages of FSP are evaluated in comparison with conventional surface modification techniques. The review concludes by identifying critical challenges and outlining future research directions for the scalable, multifunctional, and sustainable design of composite surfaces. Full article

Enhancing the local mechanical response of low-carbon cast steels remains essential for improving their performance in wear-intensive environments. In this work, a low-carbon cast steel was locally modified through the in situ formation of TiC particles via melt reaction with pressed Ti–Al–C powders. Advanced microstructural characterization (SEM/EDS, EBSD, and TEM) revealed a heterogeneous TiC-reinforced composite microstructure containing ~36 vol.% TiC with particle sizes between 0.73 and 3.88 μm. The reinforced region exhibited a substantial increase in hardness, from 160 ± 5 HV30 in the base steel to 407 ± 78 HV30, resulting from the synergistic contribution of TiC particles, fine κ-carbides, and a martensitic matrix. Nanoindentation revealed a strong mechanical contrast between phases, with TiC achieving 25.70 ± 7.76 GPa compared to 4.68 ± 1.09 GPa for the base metal matrix. Micro-abrasion tests showed a 24% reduction in wear rate, accompanied by shallower grooves and reduced plastic deformation. These findings demonstrate that in situ TiC formation, combined with κ-carbide precipitation, provides an effective strategy for improving local hardness and abrasive wear resistance in low-carbon cast steels. The results highlight the potential of in situ composite formation as an effective microstructural engineering strategy for next-generation wear-resistant cast steels. Full article

Metal-based electrical contact materials (ECMs) are essential in switching devices and rotating electrical machines, where sliding contacts enable reliable current transmission under motion. These materials must exhibit high conductivity, low friction, and wear resistance to meet industrial demands. However, their reliability is limited by wear, oxidation, arcing, and other failure mechanisms that increase contact resistance and degrade performance. To address these issues, researchers have developed self-lubricating metal matrix composites (MMCs), particularly copper (Cu) and silver (Ag)-based composites reinforced with solid lubricants such as molybdenum disulfide, tungsten disulfide, graphite, carbon nanotubes, graphene, and its derivatives. While Cu and Ag provide excellent conductivity, each has trade-offs in cost, oxidation resistance, and mechanical strength. Strategies for improving reliability involve material optimization, surface treatments, lubrication, contact design modifications, and advanced manufacturing. Although MMCs are widely reviewed, self-lubricating Ag matrix nanocomposites (AgMNCs) for sliding contacts are underexplored. This review highlights recent progress in AgMNCs produced by conventional or modern powder metallurgy techniques, focusing on the role of solid lubricants, testing conditions, and microstructure on tribological performance. Wear mechanisms, research gaps, and future directions are discussed, highlighting pathways toward the development of reliable sliding contacts. Full article

Copper (Cu) is widely used in electrical, electronic, and tribological systems owing to its excellent electrical and thermal conductivity. However, its relatively low hardness and poor wear resistance limit its use in demanding engineering applications. In this study, Cu-based hybrid metal matrix composites (MMCs) reinforced with hexagonal boron nitride (h-BN) and boron carbide (B₄C) were fabricated via spark plasma sintering (SPS) to improve their mechanical and tribological performance. The h-BN content was fixed at 1 wt.% to ensure solid lubrication, while the B₄C content was varied (0.25, 0.5, 0.75, and 1 wt.%) to examine its influence on the microstructural, mechanical, electrical, and wear properties of the composites. Microstructural analyses confirmed a homogeneous distribution of h-BN and B₄C particles in the Cu matrix at low and moderate reinforcement levels, whereas excessive B₄C resulted in partial agglomeration and reduced densification. All composites achieved relative densities above 95%, demonstrating the high densification efficiency of the SPS process. Hardness increased markedly with B₄C addition due to dispersion strengthening and grain refinement, while electrical conductivity decreased slightly because of the insulating nature of the reinforcements. Tribological tests showed that the composite containing 0.75 wt.% B₄C exhibited the best performance, with the lowest wear rate and stable friction behavior. Overall, the results indicate that co-reinforcing Cu with h-BN and B₄C through SPS is a promising strategy for developing multifunctional materials suitable for electrical contact and sliding applications. Full article

Lightweight metal matrix composites (MMCs) continue to attract significant interest due to their potential to deliver high mechanical performance at reduced weight, meeting the increasing demands of aerospace, automotive and advanced manufacturing sectors. Among these systems, aluminum-, magnesium- and titanium-based MMCs stand out for their favorable strength-to-weight ratios, corrosion resistance and versatility in processing. Although numerous studies have explored individual MMC families, the literature still lacks comparative reviews that integrate quantitative mechanical data with a broad evaluation of processing, microstructural control and application-driven performance. This review addresses these gaps by providing a comprehensive and data-driven assessment of lightweight MMCs. Recent advances in reinforcement strategies, hybrid architectures and processing routes—including friction stir processing, powder metallurgy and semi-solid techniques—are systematically examined. Emerging developments in syntactic metal foams and functionally gradient MMCs are analyzed in detail, along with practical considerations such as machinability, corrosion resistance, and high-temperature performance, integrated with AI/machine learning for predictive optimization. Overall, this work provides an integrated and critical perspective on the capabilities, limitations, and design trade-offs of lightweight MMCs, positioning them as sustainable and high-performance alternatives for extreme environments. By combining qualitative insights with quantitative meta-analyses and new experimental contributions, it offers a valuable reference for researchers and engineers seeking to optimize material selection and tailor the performance of MMCs for next-generation lightweight structures, surpassing previous reviews through holistic and innovation-driven insights. Full article