Search Results (238)

In this work, the development of Al-based metal matrix composites (MMCs) is achieved using hybrid SiC and ZrO₂ reinforcement particles for automotive applications. Powder metallurgy (PM) is employed with various combinations of important process parameters for the fabrication of MMCs. MMCs were characterized using scanning electron microscopy (SEM), X-ray diffractometry (XRD), and a microhardness study. All XRD graphs adequately exhibit Al, SiC, and ZrO₂ peaks, indicating that the hybrid MMC products were satisfactorily fabricated with appropriate mixing and sintering at all the considered fabrication conditions. Also, no impurity peaks were observed, confirming high composite purity. MMC products in all the XRD patterns, suitable for the desired applications. According to the SEM investigation, SiC and ZrO₂ reinforcement components are uniformly scattered throughout Al matrix in all produced MMC products. The occurrence of Al, Si, C, Zr, and O in EDS spectra demonstrates the effectiveness of composite ball milling and sintering under all manufacturing conditions. Moreover, an increase in interfacial bonding of fabricated composites at a higher sintering temperature indicated improved physical properties of the developed MMCs. The highest microhardness value is 86.6 HVN amid all the fabricated composites at 7% silica, 14% zirconium dioxide, 500° sintering temperature, 90 min sintering time, and 60 min milling time. An integrated Particle Swarm Optimization–Support Vector Machine (PSO-SVM) model was developed to predict microhardness based on the input parameters. The model demonstrated strong predictive performance, as evidenced by low values of various statistical metrics for both training and testing datasets, highlighting the PSO-SVM model’s robustness and generalization capability. Specifically, the model achieved a coefficient of determination of 0.995 and a root mean square error of 0.920 on the training set, while on the testing set, it attained a coefficient of determination of 0.982 and a root mean square error of 1.557. These results underscore the potential of the PSO-SVM framework, which can be effectively leveraged to optimize process parameters for achieving targeted microhardness levels for the developed Al-SiC-ZrO₂ Composites. Full article

Introducing and compacting lignocellulosic biomass in aluminum structures, though recommendable in terms of higher sustainability, the potential use of agro-waste and significant weight reduction, still represents a challenge. This is due to the variability of biomass performance and to its limited compatibility with the metal. Another question may concern possible moisture penetration in the structure, which may reduce environmental resistance and result in local degradation, such as wear or even corrosion. Despite these limitations, this hybridization enjoys increasing success. Two forms are possibly available for this: introduction into metal matrix composites (MMCs), normally in the form of char from biomass combustion, or laminate reinforcement as the core for fiber metal laminates (FMLs). These two cases are treated alongside each other in this review, first because they may represent two combined options for recycling the same biomass into high-profile structures, aimed primarily at the aerospace industry. Moreover, as discussed above, the effect on the aluminum alloy can be compared and the forces to which they are subjected might be of a similar type, most particularly in terms of their hardness and impact. Both cases considered, MMCs and FMLs involved over time many lignocellulosic residues, starting from the most classical bast species, i.e., flax, hemp, sisal, kenaf, etc., and extending also to less diffuse ones, especially in view of the introduction of biomass as secondary, or residual, raw materials. Full article

High-entropy alloy (HEA) particle-reinforced metal matrix composites (MMCs) are a new generation of MMCs with potential applications as orthopedic material in automotive, aerospace, and biomedical fields. In this study, AlCoCrFeNi HEA-reinforced Ti-6Al-4V metal matrix composites (MMCs) were prepared by microwave sintering. The microstructural aspects of the MMC were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), with an emphasis on the interdiffusion (ID) layer. The mechanical properties of the composites were studied by micro-pillar compression at the micro-length scale. The results show that the ID layer exists between the HEA particles and the matrix, is equiaxed in nature, and leads towards metallurgical bonding within the composite. The strength of this ID layer (1573 MPa of yield strength and 1867 MPa of compressive strength) and its Young’s modulus (570 MPa) were about 1.5 times lower than that of the matrix. The HEA particles exhibit the highest strength (2157 MPa of yield strength and 3356 MPa of compressive strength) and Young’s modulus (643 MPa), whereas the matrix falls in between 2372 MPa of yield strength and 2661 MPa of compressive strength, and a Young’s modulus of 721 MPa. Full article

Biodegradable magnesium-based composites show potential application in orthopedic implants, with excellent biocompatibility, low density, and biodegradable characteristics inside the human body. In this study, the stir casting procedure was employed to produce magnesium–zinc MMCs (metal matrix composites) reinforced with MgO nanoparticles, and they were characterized intensively. The analyzed compositions were Mg/4Zn, Mg/4Zn/0.4MgO, and Mg/4Zn/0.6MgO. Their mechanical properties, corrosion resistance, and microstructure were then investigated employing tensile, impact, hardness, wear, and corrosion tests, supplemented with SEM analysis. The results indicate that the Mg-4Zn-0.6MgO composite exhibited the highest performance among the tested formulations, with a tensile strength of 150 MPa, a hardness of 65 HRE (Rockwell Hardness, E-scale), and enhanced corrosion resistance. These improvements are attributed to the uniform dispersion of MgO nanoparticles and the formation of a protective Mg(OH)₂ layer, which together contribute to mechanical reinforcement and controlled degradation behavior. The combination of superior mechanical properties and customizable biodegradability verifies the engineered Mg/4Zn/0.6MgO composite as a promising candidate for a biodegradable orthopedic fixation plate without secondary surgery. Full article

This study elucidates the dynamic tribo-mechanical response of laser-cladded FeNiCr-B₄C metal matrix composite (MMC) coatings on AISI 1040 steel substrate, unraveling the intricate interplay between microstructural features and phase transformations. A multi-faceted approach, employing high-resolution scanning electron microscopy (SEM) and advanced X-ray diffraction/Raman spectroscopy techniques, provided a comprehensive characterization of the coatings’ behavior under mechanical and scratch testing, shedding light on the mechanisms governing their wear resistance. Specifically, microstructural analysis revealed uniform coatings with a columnar structure and controlled defect density, showcasing an average thickness of 250 ± 20 μm and a transition zone of 80 ± 10 μm. X-ray diffraction and Raman spectroscopy confirmed the presence of α-Fe (Im-3m), γ-FeNiCr (Fm-3m), Fe₂B (I-42m), and B₄C (R-3m) phases, highlighting the successful incorporation of B₄C reinforcement. The addition of 5 and 7 wt.% B₄C significantly increased microhardness, showing enhancements up to 201% compared to the B₄C-free FeNiCr coating and up to 351% relative to the AISI 1040 steel substrate, respectively. Boron carbide addition promoted a synergistic strengthening effect between the in situ formed Fe₂B and the retained B₄C phases. Furthermore, scratch test analysis clarified improved wear resistance, excellent adhesion, and a tailored hardness gradient. These findings demonstrated that optimized short-pulsed laser cladding, combined with moderate B₄C reinforcement, is a promising route for creating robust, high-strength FeNiCr-B₄C MMC coatings suitable for demanding engineering applications. Full article

Recent progress in metal matrix composites (MMCs) has led to significant research efforts aimed at refining reinforcement methods and processing techniques and enhancing material properties. Incorporating reinforcements has notably improved both mechanical strength and tribological performance while addressing issues such as porosity and particle agglomeration. This study investigates the impact of copper reinforcement (1–4 wt.%) on the tribological characteristics of A356 alloy under both as-cast and heat-treated conditions. The process of heat treatment involved age hardening, where the composites were solution heat treated (SHT) at 535 °C for 2 h, followed by rapid quenching and aging at 100 °C and 200 °C. The results demonstrate that increasing the copper content enhances the composite’s mechanical properties. Specifically, heat treatment promoted the redistribution of the Al₂Cu intermetallic phase during peak aging, leading to improved hardness and wear resistance. Wear testing demonstrated that heat-treated composites exhibited significantly better wear resistance than their as-cast counterparts, with improvements of 50–60% under lower loads and 80–90% under higher loads. Among the tested samples, A356 alloy reinforced with 4 wt.% copper showed the lowest wear rate across all the applied loads, along with a reduced coefficient of friction and enhanced load-bearing capacity, minimizing material deformation. Additionally, aging at 100 °C resulted in the greatest hardness and the lowest wear rate in comparison to untreated A356 alloy. These findings underscore the viability of copper-reinforced A356 composites for applications demanding enhanced mechanical characteristics and wear resistance. Full article

Tungsten–diamond metal matrix composites (MMCs) fabricated via L-PBF show potential for applications in nuclear facility shielding, heat sinks, precision cutting/grinding tools, and aerospace hot-end components. In this paper, tungsten (W), diamond (D), and diamond with Ni coating (D-Ni) powders are used to fabricate W+D and W+(D-Ni) composites by L-PBF technology. The results show that at the interface of the W+D sample, the W powder melts while the D powder remains in a solid state during L-PBF processing, and W and C elements gradually diffuse into each other. Due to the high cooling rate of L-PBF processing, the C phase forms a diamond-like carbon (DLC) phase with an amorphous structure, and the W phase becomes a supersaturated solid solution of the C element. At the interface of the W+(D-Ni) sample, the diffusion capacity of Ni and W elements in the solid state is weaker than in the molten state. C and W elements diffuse into the Ni melt, forming a rich Ni area of the DLC phase, while Ni and W elements diffuse into the solid D powder, forming a lean Ni area of the DLC phase. In the rich Ni area of the DLC phase, Ni segregation leads to the precipitation of nanocrystals (several hundred nanometers), whereas in the lean Ni area of the DLC phase, the diffusion capacity of Ni and W elements in the solid D powder is limited, resulting in nanocrystalline sizes of only about tens of nanometers. During W dendrite growth, the addition of the Ni coating and the expelling of the C phenomenon leads to W grain refinement at the interface, which reduces the number and length of cracks in the W+(D-Ni) sample. This paper contributes to the theoretical development and engineering applications of tungsten–diamond MMCs fabricated by L-PBF. Full article

Understanding wire-cut electrical discharge machining (WEDM) parameters’ impact on surface roughness (Ra) is crucial for optimizing processes. This study uses artificial neural network (ANN) techniques to estimate the surface roughness of Al/SiC composites during WEDM, examining how process parameters affect the roughness. The experiment used a stir casting aluminum alloy with a 7.5% silicon carbide metal matrix composite (MMC), adjusting parameters like the wire tension (WT), servo voltage (SV), peak current (IP), pulse on time (TON), and pulse off time (TOFF). An ANN model was created to forecast the surface roughness. The study developed an ANN model to forecast surface roughness in Al/SiC composites during WEDM, demonstrating its accuracy in identifying the link between surface finish and input parameters, thereby improving the surface quality. The ANN model accurately predicted the surface roughness based on WEDM parameters, with strong correlations between predictions and actual data, demonstrating its ability to estimate surface quality accurately. Full article

This study investigates the impact of material selection on the performance of linear slideways in ultraprecision machines used for freeform surface machining. The primary objective is to address challenges related to load-bearing capacity and limited bandwidth in slow tool servo (STS) techniques. Multi-body dynamic (MBD) simulations are conducted to evaluate the performance of two materials, alloy steel and metal matrix composite (MMC), within the linear slideway system. Key performance parameters, including acceleration, velocity, and displacement, are analyzed to compare the two materials. The findings reveal that MMC outperforms alloy steel in acceleration, velocity, and displacement, demonstrating faster response times and greater linear displacement, which enhances the capabilities of STS-based ultraprecision machining. This study highlights the potential of utilizing lightweight materials, such as MMC, to optimize the performance and efficiency of linear slideways in precision engineering applications. Full article

This work investigates the effect of the addition of tungsten carbide (WC) particles as reinforcements to Ni (Inconel 625) versus Co (Stellite 6) alloys during deposition by laser cladding to form wear-resistant metal matrix composite (MMC) coatings. While the related literature often associates the presence of WC with the enhanced wear performance of MMC coatings, this work shows that such an effect is not universal as it may critically depend on the metallic matrix employed. Thus, to demonstrate whether the reinforcement and matrix act synergically in such a scenario or not, MMC coatings formed by Inconel 625 and Stellite 6, both with WC content ranging from 10% to 40%, were deposited under the same laser cladding setup on AISI 304 stainless steel substrates, being WC-free samples produced together for comparison basis. As expected, the hardness levels increased with more WC presence in both matrices, but the wear resistance was specifically evaluated by means of the metal wheel abrasion test (ASTM B611). The results revealed that the use of WC as a reinforcement indeed affects the matrix materials differently; for Stellite 6, the wear resistance increased with up to 20% of WC (in contrast to the hardness indication), whereas for Inconel 625, the wear resistance progressively decreased with more WC content. It was observed via scanning electron microscopy (SEM) that the WC particles within the Inconel 625 alloy tended to intensive cracking, being in this way more prone to detach from the matrix and hence representing a weakening factor for the effectiveness of the coatings produced. Thus, it is concluded that the addition of WC particles, as potential reinforcements for MMC coatings, is not always effective (synergic with the matrix) in providing wear resistance, hence, opposing the prevailing consensus. This outcome and its reasons will certainly help with insights into proper design of MMC coatings, starting with the importance of matrix material selection. Full article

The current work presents the influence of the magnesiothermic synthesis method on titanium carbide (TiC). In this method, powdered titanium precursors and two carbon sources—turbostratic carbon and carbon nanotubes—were employed in proportions of 10 wt.% and 20 wt.%. The refinement of the X-ray diffraction (XRD) patterns using the Rietveld method for TiC suggests suggested coexistence of two phases, cubic with Fm-3m space group and hexagonal with P3₁21 space group. In particular, for the sample with 20 wt.% of carbon sources, the XRD refinement revealed that the cubic phase accounted for 94% of the composition, in contrast to a secondary hexagonal phase, Ti₆C_3.75, which comprised 6%. The influence of carbon on the morphology (particle size and shape) and crystallite size was monitored through bright-field transmission electron microscopy (BF-TEM) imaging and XRD. In samples containing 20 wt.% carbon, a homogeneous morphology in both size (around 11 microns) and shape was observed, along with a reduction in crystallite size (from 22.7 to 17.8 nm). Raman band analysis further revealed vibrational modes indicating that carbon induced disorder in the TiC structure. The magnesiothermic synthesis method developed in this work offers a low-cost approach of interest in the aerospace and automotive industries. Additionally, the study provides significant insights for particles used as additives or reinforcing agents to enhance the mechanical properties of metal matrix composites (MMCs). Full article

Aluminum metal matrix composites (AlMMCs) are widely employed in the aerospace and automotive industries due to their greater qualities in comparison to the base alloy. Adding nanocomposites like multi-walled carbon nanocomposites (MWCNTs) to aluminum enhances its mechanical properties. In the current research, aluminum 7075 with MWCNT particles was prepared and characterized to study its tribological behaviors, such as its hardness and specific wear rate. The experiment was designed with varying weight percentages of MWCNTs of 0.5, 1.0, and 1.5, and these were fabricated using powder metallurgy, employing compacting pressures of 300, 400, and 500 MPa and sintering temperatures of 400, 450, and 500 °C. Further, the experimental setup was designed using Design-Expert V13 to examine the impact of influencing parameters. A second-order mathematical model was developed via central composite design (CCD) using a response surface methodology (RSM), and the performance characteristics were analyzed using an analysis of variance (ANOVA). The hardness (HV) and specific wear rate (SWR) were measured using a hardness tester and pin-on-disk apparatus. From the results thus obtained, it was observed that an increase in compacting pressure and sintering temperature tends to increase the hardness and specific wear rate. An increasing weight percentage of MWCNTs increased their hardness, while the SWR was less between the weight percentages 0.9 and 1.3. A multi-objective genetic algorithm (MOGA) was trained and evaluated to provide the best feasible solutions. The MOGA suggested sixteen sets of non-dominated Pareto optimal solutions that had the best and lowest predicted values. The confirmatory analytical results and predicted characteristics were found to be excellent and consistent with the experiential values. Full article

In this work, the microstructure and degradation properties of a novel metal matrix composite composed of Mg with the addition of 1 vol. % hydroxyapatite nanopowder (Mg + 1 vol % nHAp) were evaluated. The composites in the form of discs produced using spark plasma sintering (SPS) were subjected to plastic deformation using a modified extrusion technique with an oscillating die located at the end of the extruder (called KoBo), which enables deformation without the preheating of the initial billet. The microstructure was analyzed using optical and scanning electron microscopy (SEM) with subsequent electron backscattered diffraction (EBSD) measurements. The corrosion properties were evaluated based on electrochemical and immersion tests. To assess early biological performance, cytotoxicity tests were performed. The addition of nHAp did not significantly change the corrosion rate; however, the subsequent plastic deformation greatly decreased it. Interestingly, the sample after plastic deformation without the preheating of the initial billet was characterized by the highest cell viability. Overall, the addition of nHAp improved the biological assessment of the extruded composite; however, during plastic deformation, due to the refinement of loosely adherent nHAp and the formation of bimodally distributed grain sizes, a high number of microgalvanic couples were formed, resulting in worse corrosion performance. Full article

To fulfill the harsh surface demand for key industrial components, metal matrix composite coatings (MMC) with hard ceramic particles located in the metallic matrix have attracted considerable attention in recent years. In this paper, WC/Stellite-6 composite coatings were fabricated via supersonic laser deposition (SLD). The effects of laser heating temperature, WC particle size and addition content on the deposition characteristics were systematically studied. The microstructures and mechanical properties of the as-prepared composite coatings were examined. The results demonstrated that increasing laser heating temperature can improve powder deposition efficiency for both coarse and fine WC-reinforced coatings. The peak coating height of fine WC-reinforced composite coating is 1157 μm, which is higher than that of coarse WC-reinforced composite coating (505.5 μm) deposited under the same laser heating temperature. The increase in laser heating temperature and WC addition content in original composite powder resulted in the increase in WC fraction in the composite coating, which can achieve a highest value of 55.9 vol.%. The SLD composite coating had comparable bonding strength (145.5 MPa) to that of laser cladded (LC) coating. The SLD specimen showed plastic fracture behavior, which was different from brittle fracture behavior for the LC sample. Full article