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Metal matrix composites (MMCs) with nanoparticle reinforcement provide better mechanical properties than the conventional MMCs. Stir casting is one of the most widely used fabrication techniques for MMCs. Agglomeration and wettability of reinforcement particles are some of the common problems in stir casting with nanocomposites. In this study, AA6082/B4Cp metal matrix composites have been developed by ultrasonic-assisted stir casting with addition of B4C nanoparticles as reinforcement. A Ti-based flux, potassium fluoro titanate (K2TiF6), has been used which upon reaction also acts as an in-situ reinforcement. Ultrasonic vibration has been used in the melt after mechanical stirring to obtain uniform distribution of nanoparticles. The formation of secondary phases like Al3Ti and TiSi2 improved the microstructure of the matrix as well as wettability of the B4C nanoparticles in the matrix. The effect of processing temperature, wt.% of 'B4C and K2TiF6' and vibration time and interaction of these three parameters on mechanical properties have been characterized. Box–Behnken design has been used to optimize the number of experiments. The process parameters have been optimized through response surface methodology (RSM) to achieve a balanced combination of compressive strength and failure strain in compression. With the optimum process parameters, an improvement of 22% and 144% in compressive strength and fracture strain, respectively, has been obtained when compared to AA6082 alloy. All the three parameters also affected the gain size and morphology, and a significant grain refinement has been achieved with a reduction of average grain size from 342 to 78 μm. [ABSTRACT FROM AUTHOR]

Metal matrix nanocomposites (MMNCs) are an emerging class of metals with nanosized reinforcements and have been investigated extensively in recent decades due to their promising properties for widespread applications such as aerospace, automotive, biomedical, and electronics. In this article, a comprehensive review is presented on the science and engineering aspects of MMNCs, especially the processing, microstructures, and properties of MMNCs. Common processing and manufacturing approaches and post‐processing of MMNCs are discussed. Recent advances in the unusual mechanical, physical, and chemical properties of MMNCs are reviewed. Furthermore, the latest progress on the fundamental study of interactions between nanoparticles and metals, including dispersion, pushing, and engulfment during solidification, nucleation, and phase control, is presented. It is worth noting that the exciting opportunities of nanotechnology‐enabled metallurgy (nanotech metallurgy), which have grown out of the domain of MMNCs recently, are also presented briefly. [ABSTRACT FROM AUTHOR]

Multiwalled Boron Nitride Nanotubes (BNNTs) reinforced Metal Matrix Nanocomposites (MMNCs) are discussed in this work. It is noticed that the reaction of BNNTs with Aluminum (Al) to form a compound at the interface depends on the processing condition. The processing methods include sintering, solidification, rolling, High-Pressure Torsion (HPT) and heat treatment have influenced the microstructure and mechanical properties of BNNTs filled MMNCs. The review suggests that BNNTs filled MMNCs have the potential to be used in various applications. [ABSTRACT FROM AUTHOR]

Aluminum matrix nanocomposites have been the subject of much attention due to their extraordinary mechanical properties and thermal stability. This research focuses on producing and characterizing an aluminum matrix reinforced with silicon carbide (SiC) nanometric particles. The conventional powder metallurgy route was used to produce the nanocomposites, and the dispersion and mixing process was carried out by ultrasonication. The conditions of the dispersion and the volume fraction of the SiC were evaluated in the production of the nanocomposites. Microstructural characterization was carried out using optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and electron backscatter diffraction (EBSD). Mechanical characterization was carried out using hardness and tensile tests. The dispersion agent was investigated, and isopropanol leads to better dispersion with fewer agglomerates. Increasing the volume fraction of the reinforcement improves the hardness of the nanocomposites. However, greater agglomeration of the reinforcement is observed for larger volume fractions. The greatest increase in hardness (77% increase compared to the hardness of the Al matrix) is obtained with 1.0 vol. % of SiC, corresponding to the sample with the best dispersion. The mechanical characterization through tensile tests attests to the effect of the reinforcement on the Al matrix. The main strengthening mechanisms identified were the load transfer, the texture hardening, Orowan strengthening, and the increase in the density of dislocations in the nanocomposites. [ABSTRACT FROM AUTHOR]

Ultrafine-grained Al matrix nanocomposites, reinforced with Al2O3 nanoparticles, were produced from milled powders, either by equal channel angular pressing (ECAP), at room or high temperature, with or without back pressure, or by spark plasma sintering (SPS). Their microstructures, mechanical properties (compression, hardness, and sliding wear), and thermal stabilities (thermally induced softening and cracking) were compared, and the advantages and limitations of each process discussed on a scientific but also practical point of view. For the most successful set of process parameters, the yield stress in compression reached 380 MPa, the hardness, HV = 139, remained stable up to 500 °C, and the resistance to sliding wear was comparable to that of Al 5083, and better than that of Al 7075-T6. While the samples consolidated at high temperatures (by ECAP or SPS) showed a good thermal stability, those consolidated by ECAP at room temperature were prone to thermally induced softening and cracking, which was related to trapped and pressurized gases. [ABSTRACT FROM AUTHOR]

The deformation behaviour of aluminium reinforced by carbon nanotubes (Al/CNTs) nanocomposites during cold rolling was investigated in this work. Deformation processes after production by conventional powder metallurgy routes may be an efficient approach to improve the microstructure and mechanical properties by decreasing the porosity. Metal matrix nanocomposites have enormous potential to produce advanced components, mainly in the mobility industry, with powder metallurgy being one of the most reported production processes. For this reason, it is increasingly important to study the deformation behaviour of nanocomposites. In this context, nanocomposites were produced via powder metallurgy. Advanced characterization techniques carried out the microstructural characterization of the as-received powders and produced nanocomposites. The microstructural characterization of the as-received powders and produced nanocomposites was carried out through optical microscopy (OM), and scanning and transmission electron microscopy (SEM and TEM), complemented by electron backscattered diffraction (EBSD). The powder metallurgy route followed by cold rolling is reliable for Al/CNTs nanocomposites. The microstructural characterization shows that the nanocomposites exhibit a different crystallographic orientation than the Al matrix. CNTs in the matrix influence grain rotation during sintering and deformation. Mechanical characterization revealed that during deformation, there is an initial decrease in the hardness and tensile strength for the Al/CNTs and Al matrix. The initial decrease was attributed to the Bauschinger effect being more significant for the nanocomposites. The difference in the mechanical properties of the nanocomposites and Al matrix was attributed to distinct texture evolution during cold rolling. [ABSTRACT FROM AUTHOR]

In this research, copper nanocomposites reinforced with carbon nanotubes (CNTs) were produced by ultrasonication and conventional sintering, followed by cold rolling. These nanocomposites may be good candidates due to their excellent properties for components in the electrical, electronics, or aerospace industries with highly demanding requirements. The main objectives of this work were to produce and characterize the Cu/CNT nanocomposites, identify the strengthening mechanisms, and study the deformation behavior of the nanocomposites during cold rolling. The nanocomposites exhibited an improvement in hardness and tensile strength of 17 and 67%, respectively, attesting to the strengthening effect of the reinforced material. The yield strength of the nanocomposites was determined considering different mechanisms: (1) load transfer, (2) grain refinement or texture, (3) dislocation, and (4) Orowan strengthening mechanisms. The microstructural and calculated results show that the mechanism that contributes the most to the increase in the properties of the nanocomposite is the load transfer. The nanocomposites show a different texture evolution of the Cu matrix during cold rolling. This can be due to differences in the active slip planes between the matrix and the nanocomposite, which affects the lattice rotation. [ABSTRACT FROM AUTHOR]

In the present investigation, AA5052 metal matrix nanocomposites (MMNCs) reinforced with ZrAl3 particles were fabricated using an in situ reaction. The study focuses on the effect of variation in vol.% of reinforcement particles and reaction time on phases, microstructure and tensile strength. Potassium hexafluoro zirconate (K2ZrF6) salt was used for the fabrication of 3, 6, 9 and 12 vol.% of ZrAl3 particles in the matrix. The increase in wt.% of salt and reaction time increases the vol.% of ZrAl3 particles and distributes the nanoparticles homogeneously in the matrix, respectively. Tensile strength and yield strength improved with the increase in vol.% of ZrAl3 particles and increase in reaction time. [ABSTRACT FROM AUTHOR]

Demanding requirements in automotive and aerospace applications promote the growing need to obtain materials and advanced technology capable of combining low weight with high mechanical properties. Aluminum matrix nanocomposites could be great candidates to respond to such needs. In this sense, this investigation aims to study the mechanical properties of nanocomposites of aluminum matrices reinforced with carbon nanotubes (CNTs). The nanocomposites were produced by powder metallurgy with 1.00 vol.% of reinforcement and ultrasonication as the dispersion method. Tensile, Vickers microhardness and nanoindentation tests were carried out in different sections. Microstructural characterizations were conducted in scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD) to understand and relate to the mechanical properties. An increase in the yield strength of 185% was observed for the nanocomposites, which can be attributed to the load transfer mechanism. However, the CNTs observed at the grain boundaries promote a decrease in the ductility of the nanocomposites. The mechanical behavior of the nanocomposites was further investigated by EBSD observation. The results revealed that the nanocomposites have a less extensive area of plastic deformation than the Al matrix, which is consistent with the tensile results. The presence of reinforcement affects the lattice rotation during the tensile test and the active slip systems, thus affecting their deformation behavior. [ABSTRACT FROM AUTHOR]

Metal matrix composites with a matrix of refractory metals (niobium, tungsten) and reinforcing nanodiamond particles were prepared for studying the possibility of decreasing the starting temperature of carbide synthesis. The size of primary nanodiamond particles was 4–6 nm, but they were combined in large-sized agglomerates. Mechanical alloying was used for producing the composites by crushing agglomerates and distributing nanodiamonds evenly in the metal matrix. The initial and fabricated materials were investigated by X-ray diffraction, differential scanning calorimetry, and transmission and scanning electron microscopy. Thermal processing leads to the reaction for carbide synthesis. Studies have found that the usage of carbon nanoparticles (nanodiamonds) as precursors for fabricating carbides of refractory metals leads to a dramatic decrease in the synthesis temperature in comparison with macro-precursors: lower than 200 °C for tungsten and lower than 350 °C for niobium. [ABSTRACT FROM AUTHOR]

Aluminum matrix nanocomposites have been the subject of much attention due to their extraordinary mechanical properties and thermal stability. This research focuses on producing and characterizing an aluminum matrix reinforced with silicon carbide (SiC) nanometric particles. The conventional powder metallurgy route was used to produce the nanocomposites, and the dispersion and mixing process was carried out by ultrasonication. The conditions of the dispersion and the volume fraction of the SiC were evaluated in the production of the nanocomposites. Microstructural characterization was carried out using optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and electron backscatter diffraction (EBSD). Mechanical characterization was carried out using hardness and tensile tests. The dispersion agent was investigated, and isopropanol leads to better dispersion with fewer agglomerates. Increasing the volume fraction of the reinforcement improves the hardness of the nanocomposites. However, greater agglomeration of the reinforcement is observed for larger volume fractions. The greatest increase in hardness (77% increase compared to the hardness of the Al matrix) is obtained with 1.0 vol. % of SiC, corresponding to the sample with the best dispersion. The mechanical characterization through tensile tests attests to the effect of the reinforcement on the Al matrix. The main strengthening mechanisms identified were the load transfer, the texture hardening, Orowan strengthening, and the increase in the density of dislocations in the nanocomposites.

Metal matrix nanocomposites (MMNCs) become irreplaceable in tribology industries, due to their supreme mechanical properties and satisfactory tribological behavior. However, due to the dual complexity of MMNC systems and tribological process, the anti-friction and anti-wear mechanisms are unclear, and the subsequent tribological performance prediction and design of MMNCs are not easily possible: A critical up-to-date review is needed for MMNCs in tribology. This review systematically summarized the fabrication, manufacturing, and processing techniques for high-quality MMNC bulk and surface coating materials in tribology. Then, important factors determining the tribological performance (mainly anti-friction evaluation by the coefficient of friction (CoF) and anti-wear assessment with wear rate) in MMNCs have been investigated thoroughly, and the correlations have been analyzed to reveal their potential coupling/synergetic roles of tuning tribological behavior of MMNCs. Most importantly, this review combined the classical metal/alloy friction and wear theories and adapted them to give a (semi-)quantitative description of the detailed mechanisms of improved anti-friction and anti-wear performance in MMNCs. To guarantee the universal applications of these mechanisms, their links with the analyzed influencing factors (e.g., loading forces) and characteristic features like tribo-film have been clarified. This approach forms a solid basis for understanding, predicting, and engineering MMNCs' tribological behavior, instead of pure phenomenology and experimental observation. Later, the pathway to achieve a broader application for MMNCs in tribo-related fields like smart materials, biomedical devices, energy storage, and electronics has been concisely discussed, with the focus on the potential development of modeling, experimental, and theoretical techniques in MMNCs' tribological processes. In general, this review tries to elucidate the complex tribo-performances of MMNCs in a fundamentally universal yet straightforward way, and the discussion and summary in this review for the tribological performance in MMNCs could become a useful supplementary to and an insightful guidance for the current MMNC tribology study, research, and engineering innovations. [ABSTRACT FROM AUTHOR]

Metal matrix nanocomposites (MMNCs) reinforced by carbon nanotubes (CNTs) are good candidates to produce structural components in the mobility industry, given their unique properties. The manufacture of these components can involve plastic deformation. Therefore, it is crucial to understand whether reinforcement can influence the deformation behaviour of these nanocomposites. Thus, this work aims to study the deformation behaviour of MMNCs, given their importance and the lack of studies on this topic. Although nickel is not the most widely used metal as a matrix of nanocomposites, it presents mechanical properties superior to other matrices, such as aluminium. In addition, this metal has proven to establish a strong interface and integration of carbon nanotubes, making it an exciting material for the production and study of these nanocomposites. In that sense, nickel matrix nanocomposites are reinforced by 1.00 %vol. CNTs were produced by powder metallurgy using ultrasonication as a dispersion/mixture method. For comparison purposes, a nickel matrix was produced under the same conditions. Samples with and without CNTs were cold-rolled with thickness reductions between 10 and 60% (logarithmic strains between 0.11 and 0.92) to investigate the deformation behaviour. Microstructural characterization was performed using scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD). Microhardness tests were applied to evaluate their mechanical properties. The results revealed that the nanocomposites exhibited a softening for small strains (0.11 and 0.22). This decrease in hardness was attributed to the decline in dislocation density observed by EBSD, due to the rearrangement and annihilation of pre-existing dislocations that originated during production. A possible inversion can explain the decrease in dislocation density when minor strains are applied in the dislocation or deformation trajectory, known as the Bauschinger effect. The difference in the texture evolution of the nanocomposites can be explained by the initial crystallographic orientations, which are influenced by the presence of CNTs. [ABSTRACT FROM AUTHOR]

The paper considers the development of a technological scheme for preparing metal matrix nanocomposites based on the interaction between nanodiamond reinforcing particles and a chromium matrix when being heated, forming chromium carbide nanoparticles. These carbides are in situ synthesized ceramic reinforcing nanoparticles. The first stage of preparing composites is to obtain composites with the chromium matrix and nanodiamond reinforcing particles. For this purpose, mechanical alloying is used, i.e., processing in planetary mills. The size of a primary nanodiamond particle is 5 nm, but they are combined in agglomerates that are hundreds of micrometers in size. The time of processing in the planetary mill defines the crushing degree of the agglomerates. In this study, processing was carried out for 0.5 h, 2 h, and 4 h. The second stage for obtaining composites with reinforcing particles of chromium carbides is thermal processing. Explorations using the method of differential scanning calorimetry showed that reducing the size of nanodiamond reinforcing particles (by prolonging the time of processing in the planetary mill) leads to a decrease in the initial temperature of the reaction for developing carbides. The worked-out technique for obtaining composites was patented in the Russian Federation (the patent for invention 2772480). [ABSTRACT FROM AUTHOR]

Microstructure control of in situ metal matrix nanocomposites (MMNCs) poses a barrier to their large-scale production. Here, we interrogate in unprecedented detail the formation mechanisms, morphologies, and microstructures of an in situ Al/TiC MMNC processed via salt flux reaction. Through synchrotron-based X-ray nanotomography (TXM) and scanning and transmission electron microscopy, we visualize in over five orders-of-magnitude of length-scale the TiC nanoparticles, Al 3 Ti intermetallics, and their co-locations. 3D reconstructions from TXM revealed a surprising variety of Al 3 Ti morphologies, including an orthogonal plate structure. By combining our experimental results with phase-field simulations, we demonstrate that this growth form originates from the intermetallic nucleating epitaxially on a TiC particle which is larger than a critical size at a given undercooling. Yet TiC particles that are too small to nucleate Al 3 Ti can also impact the growth of the intermetallic, by splitting the intermetallic plates during solidification. These insights on the divalent roles of the nanoparticles offer general guidelines for the synthesis and processing of MMNCs. [Display omitted] [ABSTRACT FROM AUTHOR]

A simultaneous rotational ultrasonication with mechanical stirring (RUMS) technique was applied to successfully produce aluminum alloy/hexagonal boron nitride (AA7075/h-BN) metal matrix nanocomposites (MMNCs). The rotating ultrasonic probe with a mechanical stirring impeller arrangement was employed in the casting process. The ultrasonic probe with 20 kHz frequency, 2.5 kW power, and 400 rpm rotational speed was used for the experimental work. The five variations of MMNCs (AA7075 – 0 wt.%, 0.15 wt.%, 0.3 wt.%, 0.6 wt.% and 1.0 wt% h-BN) were fabricated by RUMS process. The MMNCs were solutionized and artificially aged as per ASTM T6 heat-treatment conditions. The tensile test, Vickers microhardness, and porosity measurements were conducted. The tensile strength of RUMS-fabricated AA7075/0.6 wt% h-BN MMNC was improved by 29.46% for as-cast, and 15.90% for T6 heat-treated condition when compared with AA7075/0 wt.% h-BN as-cast and T6 heat-treated MMNCs, respectively. The microstructures and morphologies of the fractured surfaces were evaluated through optical microscopy and SEM. The elemental composition of the MMNCs was studied using SEM-EDS. The XRD was used to investigate the phase composition of the MMNCs. The dislocation density and the interfacial bonding between the matrix and reinforcements were reviewed by TEM. The presence of nano h-BN particles was confirmed by TEM-SAED and XPS techniques. The rheological effects of rotational ultrasonication and combined mechanical stirring mechanism were explained schematically. The RUMS-fabricated AA7075/0.6 wt.% h-BN MMNC showed good improvement in the mechanical properties when compared with AA7075/0.6 wt.% h-BN MMNCs synthesized by conventional mechanical stir (MS) and ultrasonic (UT) assisted casting process. The enhancement in mechanical properties of RUMS-synthesized MMNCs is attributed to the amalgamated effect of ultrasonic transient cavitation and rotational acoustic streaming along with vortex motion in the novel RUMS fabrication process, which have assisted in dendritic fragmentation, and accelerated the refinement of grains to achieve consistent scattering of nano h-BN particulates without any agglomeration. [ABSTRACT FROM AUTHOR]

The investigation of surface roughness in machined materials/products has proven to be a difficult undertaking. The surface quality is determined not only by the parameters but also by the cutting conditions. Surprisingly, a study indicated that when analysing the quality of machining processes currently being done, surface morphology has a significant impact on tool performance. PCD (Polycrystalline diamond) and PCBN (Poly cubic boron nitride) cutting tools produce a better surface finish, which is explored in the machining of Al-Mg/Zr/TiO2 (15%), nano metal matrix composites (NMMC). The study primarily focuses on determining the best parameters for end milling NMMCs in tests for long-term production sustainability. Using scanning electron microscopy, microstructural study of the machined surface will aid in finding the parameters responsible for the cause of surface integrity. The work focusses on analysing tool performance by monitoring the machining process in real time using signal characteristics, forecasting vibrations (displacement) and machine outputs using surface topography and chip analysis. The tool failure was acquired by establishing a correlation between displacement (vibrations) and post machining outcome of experimental study, as a result, the evolution of displacement in the PCBN tool is 24.7 μm, which is better compared to 34.3 μm in the PCD tool at 3000 r/min. PCBN outperformed PCD with a 1.82 μm surface roughness, resulting in longer tool life. Thus, this economical reliable empirical method the problem of finding difficulty identifying the causing of tool wear and failure by correlating sensor signals features with experimental results. [ABSTRACT FROM AUTHOR]

A fruitful combination of powder metallurgy and the mechanical alloying route is one of the most promising process for producing advanced Cu-based nanocomposites. In this study, three different material systems, namely, pure copper (Cu), 5 wt% Cr reinforced Cu matrix composites, and 1 wt% Y2O3 reinforced Cu–Cr matrix nanocomposites were synthesized by ball milling method at different milling times. The influence of different ball milling times (0.5, 2, and 4 h) and different types of reinforcements (Cr and Y2O3) on the powder and sintered parts properties were thoroughly analyzed with a holistic approach. The milled powders were then consolidated using a cold press followed by a liquid phase sintering process. Results revealed that the Cr and Y2O3 particles were fractionally dispersed and imbedded in the ductile Cu matrix with respect to increasing milling time. Milling for 4 h of Cu–Cr–Y2O3 powders produced the lowest level of particle size (28 µm) with reduced and flattened and uniformly distributed reinforcement phases due to intense plastic deformation induced shearing effect and dominant powder-ball-jar collisions. Besides, the ball milling process of the same powders concluded a decrement of crystallite size to 35 nm in concomitant with an increase of lattice strain and dislocation density ⁓ % 0.3 and 0.8 × 1015 line/m2, respectively. Brinell hardness of the sample produced by these powders increased from 39 to 95 HB. A ⁓%145 striking increase of hardness could be attributed to the strong hindrance of high-dense dislocations triggered by several concurrent strengthening mechanisms. Nevertheless, relative density results of sintered samples revealed that the addition of Cr and Y2O3 along with increasing milling time deteriorated the density due to the higher hardness and brittleness of milled powders and accompanying worsened compressibility and sinterability. The source of noticed differences between hardness and density results were discussed within the process-structure-performance framework. [ABSTRACT FROM AUTHOR]

The possibility of applying globular carbon for reinforcing the aluminum matrix when using mechanical alloying to produce composites was shown by investigating specific properties of chemical interaction of nanocarbon with the aluminum matrix. The structure of the initial particles of globular carbon and composite granules was studied. Mechanical alloying can significantly crush the initial particles of globular carbon. The use of the method of differential scanning calorimetry allowed the temperature of the start of the reaction between globular carbon nanoparticles and aluminum matrix with the formation of aluminum carbide to be determine as 320 °C–350 °C. Aluminum matrix composites with reinforcing particles of globular carbon can be used up to these temperatures without risk of the formation of aluminum carbide. [ABSTRACT FROM AUTHOR]

This paper presents a machine learning model to predict the effect of Al2O3 nanoparticles content on the wear rates in Cu-Al2O3 nanocomposite prepared using in situ chemical technique. The model developed is a modification of the random vector functional link (RVFL) algorithm using artificial hummingbird algorithm (AHA). The objective of using AHA is used to find the optimal configuration of RVFL to enhance the prediction of Al2O3 nanoparticles. The preparation of the composite was done using aluminum nitrate that was added to a solution containing scattered copper nitrate. After that, the powders of CuO and Al2O3 were obtained, and the leftover liquid was removed using a thermal treatment at 850 °C for 1 h. The powders were consolidated using compaction and sintering processes. The microhardness of the nanocomposite with 12.5% Al2O3 content is 2.03-fold times larger than the pure copper, while the wear rate of the same composite is reduced, reaching 55% lower than pure copper. These improved properties are attributed to the presence of Al2O3 nanoparticles and their homogenized distributions inside the matrix. The developed RVFl-AHA model was able to predict the wear rates of all the prepared composites at different wear load and speed, with very good accuracy, reaching nearly 100% and 99.5% using training and testing, respectively, in terms of coefficient of determination R2. [ABSTRACT FROM AUTHOR]

In the present work, metal matrix nanocomposites are being prepared using Fe as base material reinforced with Al2O3 and doped with CeO2. Nanocomposite specimens were synthesized using powder metallurgy technique. Tafel Polarization, Corrosion Behavior and its optimization using Analysis of Variance (ANOVA) as well as Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) along with Phase and Microstructure of prepared samples have been investigated. It was observed that corrosion rate and corrosion current density was highest for pure Fe samples whereas 1.0% CeO2 doped Fe-Al2O3 metal matrix nanocomposite system showed the formation of nano amorphous layer on the specimen surface. Analysis of Variance shows that the different compositions of samples have changed outcome on corrosion behavior. Technique for Order of Preference by Similarity to Ideal Solution analysis shows ordered preference of sample as per the readings of corrosion rate. [ABSTRACT FROM AUTHOR]

This paper presents a machine learning model to predict the effect of Al2O3 nanoparticle content on the coefficient of thermal expansion in Cu-Al2O3 nanocomposites prepared using an in situ chemical technique. The model developed is a modification of Long Short-Term Memory (LSTM) using dwarf mongoose optimization (DMO), which mimics the behavior of DMO to find its food for predicting the behavior of the composite. The swarm of DMO consists of three groups, namely the alpha group, scouts, and babysitters. Each group has its own behavior to capture the food. The preparation of the nanocomposite was performed using aluminum nitrate that was added to a solution containing scattered copper nitrate. After that, the powders of CuO and Al2O3 were obtained, and the leftover liquid was removed using thermal treatment at 850 °C for 1 h. The powders were consolidated using compaction and sintering processes. The impact of Al2O3 contents on the thermal properties of the Cu-Al2O3 nanocomposite was investigated. The results showed that the Thermal Expansion Coefficient (TEC) decreases with increasing Al2O3 content due to the increased precipitation of Al2O3 nanoparticles at the grain boundaries of the Cu matrix. Moreover, the good interfacial bonding between Al2O3 and the Cu may participate in this decrease in TEC. The proposed machine learning model was able to predict the TEC of all the produced composites with different Al2O3 content and was tested at different temperatures with very good accuracy, reaching 99%. [ABSTRACT FROM AUTHOR]

Micromechanics model, finite element (FE) simulation of microindentation and machine learning were deployed to predict the mechanical properties of Cu–Al 2 O 3 nanocomposites. The micromechanical model was developed based on the rule of mixture and grain and grain boundary sizes evolution to predict the elastic modulus of the produced nanocomposites. Then, a FE model was developed to simulate the microindentation test. The input for the FE model was the elastic modulus that was computed using the micromechanics model and wide range of yield and tangent stresses values. Finally, the output load-displacement response from the FE model, the elastic modulus, the yield and tangent strengths used for the FE simulations, and the residual indentation depth were used to train the machine learning model (Random vector functional link network) for the prediction of the yield and tangent stresses of the produced nanocomposites. Cu–Al 2 O 3 nanocomposites with different Al 2 O 3 concentration were manufactured using insitu chemical method to validate the proposed model. After training the model, the microindentation experimental load-displacement curve for Cu–Al 2 O 3 nanocomposites was fed to the machine learning model and the mechanical properties were obtained. The obtained mechanical properties were in very good agreement with the experimental ones achieving 0.99 coefficient of determination R2 for the yield strength. [ABSTRACT FROM AUTHOR]

Ultrafine-grained Al matrix nanocomposites, reinforced with Al2O3 nanoparticles, were produced from milled powders, either by equal channel angular pressing (ECAP), at room or high temperature, with or without back pressure, or by spark plasma sintering (SPS). Their microstructures, mechanical properties (compression, hardness, and sliding wear), and thermal stabilities (thermally induced softening and cracking) were compared, and the advantages and limitations of each process discussed on a scientific but also practical point of view. For the most successful set of process parameters, the yield stress in compression reached 380 MPa, the hardness, HV = 139, remained stable up to 500 °C, and the resistance to sliding wear was comparable to that of Al 5083, and better than that of Al 7075-T6. While the samples consolidated at high temperatures (by ECAP or SPS) showed a good thermal stability, those consolidated by ECAP at room temperature were prone to thermally induced softening and cracking, which was related to trapped and pressurized gases.

In this research, copper nanocomposites reinforced with carbon nanotubes (CNTs) were produced by ultrasonication and conventional sintering, followed by cold rolling. These nanocomposites may be good candidates due to their excellent properties for components in the electrical, electronics, or aerospace industries with highly demanding requirements. The main objectives of this work were to produce and characterize the Cu/CNT nanocomposites, identify the strengthening mechanisms, and study the deformation behavior of the nanocomposites during cold rolling. The nanocomposites exhibited an improvement in hardness and tensile strength of 17 and 67%, respectively, attesting to the strengthening effect of the reinforced material. The yield strength of the nanocomposites was determined considering different mechanisms: (1) load transfer, (2) grain refinement or texture, (3) dislocation, and (4) Orowan strengthening mechanisms. The microstructural and calculated results show that the mechanism that contributes the most to the increase in the properties of the nanocomposite is the load transfer. The nanocomposites show a different texture evolution of the Cu matrix during cold rolling. This can be due to differences in the active slip planes between the matrix and the nanocomposite, which affects the lattice rotation.

Demanding requirements in automotive and aerospace applications promote the growing need to obtain materials and advanced technology capable of combining low weight with high mechanical properties. Aluminum matrix nanocomposites could be great candidates to respond to such needs. In this sense, this investigation aims to study the mechanical properties of nanocomposites of aluminum matrices reinforced with carbon nanotubes (CNTs). The nanocomposites were produced by powder metallurgy with 1.00 vol.% of reinforcement and ultrasonication as the dispersion method. Tensile, Vickers microhardness and nanoindentation tests were carried out in different sections. Microstructural characterizations were conducted in scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD) to understand and relate to the mechanical properties. An increase in the yield strength of 185% was observed for the nanocomposites, which can be attributed to the load transfer mechanism. However, the CNTs observed at the grain boundaries promote a decrease in the ductility of the nanocomposites. The mechanical behavior of the nanocomposites was further investigated by EBSD observation. The results revealed that the nanocomposites have a less extensive area of plastic deformation than the Al matrix, which is consistent with the tensile results. The presence of reinforcement affects the lattice rotation during the tensile test and the active slip systems, thus affecting their deformation behavior.

Metal matrix composites with a matrix of refractory metals (niobium, tungsten) and reinforcing nanodiamond particles were prepared for studying the possibility of decreasing the starting temperature of carbide synthesis. The size of primary nanodiamond particles was 4–6 nm, but they were combined in large-sized agglomerates. Mechanical alloying was used for producing the composites by crushing agglomerates and distributing nanodiamonds evenly in the metal matrix. The initial and fabricated materials were investigated by X-ray diffraction, differential scanning calorimetry, and transmission and scanning electron microscopy. Thermal processing leads to the reaction for carbide synthesis. Studies have found that the usage of carbon nanoparticles (nanodiamonds) as precursors for fabricating carbides of refractory metals leads to a dramatic decrease in the synthesis temperature in comparison with macro-precursors: lower than 200 °C for tungsten and lower than 350 °C for niobium.

The paper considers the development of a technological scheme for preparing metal matrix nanocomposites based on the interaction between nanodiamond reinforcing particles and a chromium matrix when being heated, forming chromium carbide nanoparticles. These carbides are in situ synthesized ceramic reinforcing nanoparticles. The first stage of preparing composites is to obtain composites with the chromium matrix and nanodiamond reinforcing particles. For this purpose, mechanical alloying is used, i.e., processing in planetary mills. The size of a primary nanodiamond particle is 5 nm, but they are combined in agglomerates that are hundreds of micrometers in size. The time of processing in the planetary mill defines the crushing degree of the agglomerates. In this study, processing was carried out for 0.5 h, 2 h, and 4 h. The second stage for obtaining composites with reinforcing particles of chromium carbides is thermal processing. Explorations using the method of differential scanning calorimetry showed that reducing the size of nanodiamond reinforcing particles (by prolonging the time of processing in the planetary mill) leads to a decrease in the initial temperature of the reaction for developing carbides. The worked-out technique for obtaining composites was patented in the Russian Federation (the patent for invention 2772480).

Metal matrix nanocomposites (MMNCs) reinforced by carbon nanotubes (CNTs) are good candidates to produce structural components in the mobility industry, given their unique properties. The manufacture of these components can involve plastic deformation. Therefore, it is crucial to understand whether reinforcement can influence the deformation behaviour of these nanocomposites. Thus, this work aims to study the deformation behaviour of MMNCs, given their importance and the lack of studies on this topic. Although nickel is not the most widely used metal as a matrix of nanocomposites, it presents mechanical properties superior to other matrices, such as aluminium. In addition, this metal has proven to establish a strong interface and integration of carbon nanotubes, making it an exciting material for the production and study of these nanocomposites. In that sense, nickel matrix nanocomposites are reinforced by 1.00 %vol. CNTs were produced by powder metallurgy using ultrasonication as a dispersion/mixture method. For comparison purposes, a nickel matrix was produced under the same conditions. Samples with and without CNTs were cold-rolled with thickness reductions between 10 and 60% (logarithmic strains between 0.11 and 0.92) to investigate the deformation behaviour. Microstructural characterization was performed using scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD). Microhardness tests were applied to evaluate their mechanical properties. The results revealed that the nanocomposites exhibited a softening for small strains (0.11 and 0.22). This decrease in hardness was attributed to the decline in dislocation density observed by EBSD, due to the rearrangement and annihilation of pre-existing dislocations that originated during production. A possible inversion can explain the decrease in dislocation density when minor strains are applied in the dislocation or deformation trajectory, known as the Bauschinger effect. The difference in the texture evolution of the nanocomposites can be explained by the initial crystallographic orientations, which are influenced by the presence of CNTs.

The ability to produce metal matrix nanocomposites via pressing and infiltration was validated. Al/TiC nanocomposite was used as the model material. Pressing the powder in a die yielded cylindrical specimens with a green density of 1.98 ± 0.05 g/cm³, which was increased to only 2.11 ± 0.12 g/cm³ by sintering. Direct infiltration of the pressed specimens at 1050 °C for 3.5 h yielded specimens with a density of 3.07 ± 0.08 g/cm³, an open porosity of 3.06 ± 1.40%, and an areal void fraction of 8.09 ± 2.67%. The TiC nanoparticles were verified to be well dispersed using energy-dispersive X-ray spectroscopy. The measured hardness of 64 ± 3 HRA makes it a promising material for structural applications in industries such as aerospace and automotive. [ABSTRACT FROM AUTHOR]

In the current scenario, the development of high strength and low weight material is the demand of the aerospace defence organizations. Magnesium alloy based composite has low density, good mechanical and physical properties. In this study, magnesium alloy AZ31B is used as reinforcement material and graphene nanoparticle is used as reinforcement material. Stir casting technique is used for the development of composite material. Three weight percentages i.e. 0.4%, 0.8% and 1.2% are used for the casting. The microstructural analysis is performed to validate the presence of graphene particles in the developed composite. Further mechanical properties such as tensile strength, hardness and toughness are evaluated. Experimental results confirm that GNPs particles are uniformly distributed into the matrix material. It was observed that due to the reinforcement of GNPs particles tensile strength of the material is improved by 31.17%, hardness is improved about 46.9%. However, the peak value of toughness is observed 12.6 Jule/cm2 in the matrix material, it decreases by increasing the wt% of reinforcement particle and lowest value of toughness of 6.82 Jule/cm2 is observed in AZ31B/1.2%GNP composite. [ABSTRACT FROM AUTHOR]

The present paper reports the effect of plain strain deformation on grain strengthening mechanism of iron (Fe) - alumina (Al2O3) Metal Matrix Nanocomposites (MMNCs) fabricated through powder metallurgical (P/M) processing. Specimens for the present study were weighed in required amount, ball milled, compacted at a load of 5, 6 and 7 tons followed by sintering in an atmospheric controlled furnace at 1100 °C for 1 hour. Plain strain deformation of samples was carried out at a load of 5 tons under different interfacial condition i.e. dry, solid lubricant and liquid lubricant. XRD studies reveal the formation of iron, alumina and nano iron-aluminate (FeAl2O4) phases respectively. Maximum average sintered density investigated for the specimen is found to be 4.6179 gm/cc compacted under 7 tons of load and minimum sintered density is found to be 4.4572 gm/cc for specimen compacted under 5 tons of load. Overall, fabricated Fe-Al2O3 metal matrix nanocomposites with powder metallurgy route when characterized for plain strain deformation shows strengthening between grain and grain boundary which can be a good candidate material for application in railways especially while designing railway structures and tracks. [ABSTRACT FROM AUTHOR]

Ni-Ti-C metal matrix composites (MMCs) with in situ formed, homogeneously distributed titanium carbide (TiC), as well as graphite (C) reinforcement in the nickel metal matrix, were synthesized using mechanical alloying (MA) followed by spark plasma sintering (SPS). The main objective of this research is to consolidate Ni-Ti-C MMCs with varying C/Ti ratio and characterize the MMCs to investigate the altered mechanical and tribological behavior in comparison with pure nickel. Experimental results showed that these composites possess a refined microstructure in addition to the presence of hard TiC precipitates within the nickel matrix. Additionally, by tailoring the C/Ti ratio in these composites, an additional graphitic phase is engineered into the microstructure. All Ni-Ti-C nanocomposites exhibited excellent microhardness as well as enhanced tribological performance compared to pure nickel. The increased mechanical properties are primarily attributed to the presence of in situ formed nanoscopic TiC and graphite reinforcing the nickel matrix. [ABSTRACT FROM AUTHOR]

Metal matrix nanocomposites for selective laser melting were prepared by electrodeposition. The nanoparticles studied include alumina (Al2O3), silicon carbide (SiC), zirconia (ZrO2) and yttria (Y2O3). Based on nickel, the effects of different nanoparticles prepared by electrodeposition on dispersion and incorporation were studied. The effects of electrodeposition parameters on Ni/Al2O3 nanocomposites were further studied. The results showed that the optimal effect was obtained at the concentration of 10 g/L and ultrasonic amplitude of 23 µm. Microhardness test showed that the addition of Nano-Al2O3 significantly improved the mechanical properties of nickel base alloy. The average Vickers hardness of pure nickel (HV0.05) was 153.9 kg/mm², and that of Ni/Al2O3 the surface roughness of pure nickel decreased from 254 nm to 107 nm, while that of Ni/Al2O3 nanocomposites decreased from 323 nm to 72 nm. Simultaneously, Al2O3 particles can be evenly distributed without obvious agglomeration. [ABSTRACT FROM AUTHOR]

In the present work, phase, microstructure, and wear properties of Al2O3-reinforced Fe–Si alloy-based metal matrix nanocomposites have been studied. Composites using 2 wt.% and 5 wt.% of Si and rest Fe powder mix were synthesized via powder metallurgy and sintered at different temperature schedules. Iron–silicon alloy specimens were found to have high hardness and high wear resistance in comparison to pure iron specimens. Addition of 5 wt.% and 10 wt.% alumina reinforcement in Fe–Si alloy composition helped in developing iron aluminate (FeAl2O4) phase in composites which further improved the mechanical properties i.e. high hardness and wear resistance. Formation of iron aluminate phase occurs due to reactive sintering between Fe and Al2O3 particles. It is expected that the improved behavior of prepared nanocomposites as compared to conventional metals will be helpful in finding their use for wide industrial applications. [ABSTRACT FROM AUTHOR]

Metal matrix nanocomposites are a newly developed materials with promising applications in a wide variety of areas, ranging from medical to aerospace structures, owing to their lightweight high-strength properties. A light metal like aluminum is usually strengthened by a reinforcing agent of carbides, nitrides, oxides, carbon-based materials, or even elementals to boost the mechanical performance without sacrificing lightweight; however, almost all reinforcing nanomaterials are commonly poorly wetted by metals leading to agglomerations, clusterings, among other problems, with diminished ductility and overall mechanical performance. To tackle the mentioned problems, a number of strategies including coatings, thermal, mechanical, or chemical treatments may be followed. In the present study, a particular focus is paid on the mechanical dispersion of nano-silica particles in a molten A356 alloy through applying high-intensity ultrasonic agitations in order to improve dispersibility, wettability, and interfacial affinity. Nano-silica being an inexpensive high-strength nanomaterial is added to an A356 aluminum alloy melt and then dispersed and distributed by a 2-kW power ultrasonic system. Experimental results including microscopic observations and those mechanical experimentations revealed that the ultrasonication of the aforesaid solid–liquid system may greatly improve the affinity between the de-agglomerated nano-silica particles and the host aluminum matrix with enhanced ductility.