This work demonstrates a novel approach for tailoring the phase architecture and mechanical response of TiAl intermetallics through high-entropy alloy (HEA) particle reinforcement combined with spark plasma sintering (SPS). The TiAl matrix retained a stable gamma-TiAl + alpha(2)-Ti3Al lamellar structure across the sintering range (850-950 degrees C), while the FCC HEA phase remained finely dispersed at 850-900 degrees C and developed detectable FCC HEA reflections at 950 degrees C, consistent with an HEA-rich FCC solid solution phase retained after SPS, and forming a gamma + alpha(2) + FCC multiphase architecture. Increasing sintering temperature significantly improved densification and mechanical performance, achieving similar to 99 +/- 0.04% relative density, similar to 351 +/- 14.2 HV microhardness, similar to 702 +/- 7 MPa flexural strength, and similar to 560 +/- 7 MPa tensile strength, with fracture strain increasing to similar to 1.6%. These improvements are associated with reduced porosity, enhanced lamellar continuity, improved matrix-reinforcement bonding, and the presence of FCC HEA domains that may assist local strain accommodation. Overall, the study demonstrates that SPS-assisted phase and microstructural engineering enable a synergistic strength-ductility response in HEA-reinforced TiAl composites, highlighting their potential as lightweight high-temperature structural materials for turbine and aerospace applications.

In this study, powder Al70(CrMgNi)30 medium entropy alloy (MEA) was mixed with powder aluminium-7068 (AA-7068) at 0, 5, 10, and 15 wt% to improve its mechanical performance. The powders were blended in a tubular mixer at 110 rev/min for 8 hours, compacted at 50 MPa for 10 mins and vacuum sintered at 550 & ring;C. The sintered composites were evaluated, and the outcome indicated that 5 and 10 wt% MEA diffused more in the AA7068 matrix; however, 15 wt% MEA exhibited particle clusters combined with decreasing grain size. The addition of 5 and 10 wt% MEA reduces the porosity, while 15 wt% MEA increases porosity somewhat. Conclusively, 0-15 wt% MEA increased density, hardness, and elastic modulus but linearly decreased elongation of AA-7068 alloy. 0 - 10 wt% MEA improved yield and ultimate tensile strengths, fracture toughness, and impact strength; however, adding 15 wt% MEA led to a minor decrease in strength. The obtained wear rate of the composites declined with a proportional rise in MEA dosage, though it increases with applied load. Thus, the MEA dose of 10 % results in a beneficial overall improvement in the AA-7068 alloy compared to other percentage reinforcements.

Metal matrix composites (MMCs) have become increasingly crucial in high‐performance applications due to their superior properties like outstanding wear resistance, high specific strength, and low thermal expansion. This review comprehensively examines the machining of MMCs, focusing on both conventional and nonconventional techniques. Conventional methods, including turning, milling, drilling, and grinding, are discussed alongside their inherent challenges and limitations. Nonconventional methods such as abrasive water jet machining (AWJM), ultrasonic machining (USM), electrical discharge machining (EDM), electrochemical machining (ECM), and laser beam machining (LBM) are evaluated for their effectiveness in overcoming these challenges. Recent advances and emerging trends in the field are highlighted, with particular emphasis on hybrid machining techniques, nanomachining, micromachining, and the integration of additive manufacturing with machining processes. The transformative role of artificial intelligence (AI) and machine learning (ML) in process optimization is explored, showcasing improvements in precision, tool wear reduction, and surface quality. Additionally, the review addresses the growing importance of sustainability and green machining practices, underscoring the need for environmentally friendly manufacturing approaches. The paper identifies current challenges in machining MMCs, such as tool wear, process instability, and the complexity of modeling MMC behavior. Innovations needed to overcome these challenges are discussed, including the development of advanced tool materials, coatings, and enhanced modeling techniques. Potential areas for future research are proposed, emphasizing the need for continued exploration of nano‐enhanced MMCs, multiscale modeling, and the integration of AI‐driven process controls. In conclusion, this review provides a detailed overview of the state of the art in MMC machining, highlights significant advancements, and offers recommendations for both practitioners and researchers to drive future innovations in the field.

High-entropy alloys (HEAs) have emerged as promising materials with exceptional mechanical properties, thus, making them suitable for demanding applications that require high strength and toughness. This review highlights the latest advancements in HEA research, focusing on processing techniques, microstructural evolution, and mechanical properties and behavior techniques. The unique HEA composition comprising four or more principal elements in almost equiatomic ratios produces high configurational entropy, which stabilizes distinct solid solution phases. This stabilization leads to microstructures distinguished by disorder and set of defect types, generating superior mechanical properties. For several years, substantial advancement has been achieved in HEA processing routes, from traditional casting and powder metallurgy to state-of-the-art methods such as additive manufacturing and severe plastic deformation. These processes, combined with a developing understanding of microstructural evolution and phase transformations, are broadening the potential application of HEAs in aerospace, energy, and automotive. As the field progresses, the implications of these findings are shaping future research directions and expanding the potential applications of HEAs in various industries. This review underscores the current challenges in tailoring the microstructure of HEAs and optimizing their mechanical functionality, laying the foundation for future innovations and practical use.

Metal particles are gaining attention as reinforcement in metal matrix composites owing to their ductility as compared with ceramic particles, which are inherently brittle. High-entropy-alloy (HEA) particles belong to this category based on their high strength, ductility, and thermal stability. Aluminium-7068 is a new aerospace alloy in the 7000 series that possesses higher strength than aluminium-7075, yet very few studies have considered reinforcement with high-entropy alloy particles. For strength improvement, NiTiFeAlCu (HEA) powder was introduced into the aluminium-7068 matrix at 0, 4, 8, and 12 wt. % at 500 degrees C via vacuum sintering. The microstructure depicted dispersed particles in the matrix with a linear reduction in porosity as the HEA dosage increased. Consequently, there was a linear increase in density and relative density. 4-12 wt.% HEA engendered linear improvements in yield and ultimate tensile strength, elastic modulus, and hardness; meanwhile, elongation was a progressive decline. The outcome of this study shows that HEA particles in AA-7068 resulted in an improvement of the tensile and hardness properties. The particle addition was observed to reduce the composite's friction coefficient and wear rate. This report revealed that the performance of AA-7068 can be improved up to 12 wt. % NiTiFeAlCu HEA addition.

Materials properties are highly dependent on the processing parameters and technique used during sintering. The effect of Spark Plasma sintering process parameters (pressure and temperature) on the hardness and relative density of Ni-20Cr-5ZrO2 composite was investigated. Response Surface Methodology (RSM) from the design of experiment (DOE) technique was successfully employed for the experimental design, and statistical analysis was conducted on the obtained experimental results. The microstructural analysis of the sintered composite showed the presence of solid solution phases of Ni and Cr, which were confirmed by the XRD results as (Cr,Ni) alongside unreacted ZrO2 particles at sintering temperatures of 950 degrees C and 1000 degrees C. The validity of the model developed with the impact of each variable and their corresponding interaction on the responses was performed using analysis of variance (ANOVA). The relative density and hardness were the two responses considered. The actual values (experiment data) and expected values (simulated data) were subjected to statistical analysis, to develop a predictive model that synchronizes density and hardness as distinct process parameters, with material hardness and relative density serving as the responses of the specified experiment. For the responses, quantitative models were created, and 10 experimental runs were processed to ascertain the desirability of the responses. The SPS processing parameters considered the most desirable were 1000 degrees C sintering temperature and 50 MPa pressure. The hardness property obtained under this condition is 433.23 HV with a relative density of 98.15%. (c) 2023 The Authors. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

Reprocessing municipal wastes into useful engineering components is one way to reduce their environmental impact. This paper presents a report on an alternative experimental approach to reprocessing common environmental wastes like aluminum scraps, steel shavings, and coconut shells into eco-friendly engineering composite. Equally, response surface analysis was incorporated in the development and validation of predictive models fit for future prediction of response properties. Aluminum scrap was heated into a liquid state and reinforced with recycled steel particles (RSP) and coconut shell ash particles (CSP) at varying proportions. Specimen design involves three group mixes: A, B, and C. Each of the three groups mixes comprised 0, 1, and 2 % RSP at constant dosage, respectively. Meanwhile, each mix was incorporated with 4, 8, and 12 wt % CSP. The microstructural features, physical (porosity, density, and relative density), and mechanical (tensile strength, hardness, elastic modulus, fracture toughness, impact strength, and percentage ductility) properties were appraised. The outcome revealed that the combination of the two reinforcements (RSP and CSP) contributed to microstructural evolution within the specimens. The porosities of the composite specimens were reported to marginally increase with the reinforcement combination. Interestingly, the composite exhibited lighter weight with improved mechanical performance. Mathematical models derived for the response properties were certified fit for future analysis and predictions. Meanwhile, the optimization procedure revealed that the combination of 1.3 % RSP and 6.7 % CSP was suitable for the design of optimal recycled aluminum composites for sustainable engineering designs. The results clarified that the reinforcement particles (RSP and CSP) are low-cost alternatives to synthetic ceramic reinforcements in the aluminum composite."

Oxonitridoaluminosilicates (SiAlON) are renowned in advanced ceramics for their exceptional properties: high temperature stability, excellent oxidation resistance, and good wear resistance. Incorporating micro- and nano-sized fillers into SiAlON matrices enhances their properties, yielding SiAlON composite materials with superior mechanical, tribological, and thermal characteristics. This review examines fabrication techniques for producing SiAlON micro/nanocomposites and the structure-property relationships governing their performance across different phase compositions (β, α, X, and O-phases). A comprehensive literature review scrutinized fabrication techniques and structure-property relationships from various databases and scholarly articles. Although SiAlON composites with micro/nano inclusions hold promise across applications, understanding their fabrication processes, structure-property relationships, and potential applications in different fields is crucial. The review highlights diverse fabrication techniques for SiAlON micro/nanocomposites and provides insights into their structure-property relationships. Additionally, emerging applications in structural domains, cutting tools, coatings, corrosion protection, solar cells, LEDs, biomedical realms, and filtration membranes are discussed. This review is a valuable resource for researchers and engineers interested in designing SiAlON products tailored for sophisticated applications. It emphasizes understanding fabrication processes and structure-property relationships to unlock SiAlON-based materials' full potential across industries.

AZ91D-Ni-graphene nanoplatelets (GNPs) Mg-based composites were effectively consolidated using spark plasma sintering (SPS). The - reinforcement in the AZ91D Mg alloy varies from 0 wt% to 2 wt%, with Ni constituent fixed at 1.5 wt%. Scanning electron microscope, Transmission electron microscope, X-ray diffraction and Raman spectroscopy were utilised to investigate the morphology of the powder and sintered compact. The synergistic strengthening offered by the inclusion of GNPs comprising grain refinement (ΔσHall−Petch), load transfer from AZ91D-Ni Mg-based alloy matrix to GNPs reinforcement (ΔσLT), dislocations strengthening due to the mismatch in the coefficient of thermal expansion (CTE)(ΔσCTE), modulus mismatch (Δσmm), and strengthening due to Orowan (Δσorowan) was investigated. Experimental results indicate that the addition of GNPs contributes minimally to the densification of the compacts, increasing from 97% to 98.1% with increasing GNPs. However, significant improvements were obtained for other properties investigated, such as a microhardness, which increased from 67.4 to 89.7 H V, nano hardness from 4744.9 to 18,251.3 MPa, an elastic modulus from 84.53 to 243.75 GPa and wear rate from 5.21 × 10−3 to 3.85 × 10−3 mm3/N/m under 10 N load with an increase in GNPs content. This study establishes the capability of GNPs as efficient reinforcement in manufacturing metal matrix composites with enhanced mechanical and tribological properties.

This study examines the nanomechanical and anti-wear behaviour of spark plasma sintered Ti6Al4V matrix composites reinforced with Ni and SiC particles. Microstructural analysis revealed the in-situ formation of the hard TiC, Ti3SiC2 and Ti5Si3 phases within the metal matrix. Nanoindentation analysis revealed that the composite containing 10 wt% SiC (TNi10SiC) exhibited significantly higher nanohardness (about 10.3 GPa) and elastic modulus (similar to 177.7 GPa) than the unreinforced Ti6Al4V alloy (sample T). The improved nanomechanical performance of the composites was attributed to the load-carrying capacity of the hard, in-situ formed reinforcement phases. The anti-wear characteristics of the composites showed that TNi5SiC composite displayed superior wear resistance with a specific wear rate of 4.75 +/- 0.34 x 10(-4) mm(3)/Nm and 2.15 +/- 0.34 x 10(-4) mm(3)/Nm under an applied loads of 10 N and 20 N, respectively, among the sintered samples. This represents about 67% and 29% reduction in specific wear rate relative to sample T. This enhanced tribological behaviour was ascribed to the increased surface hardness, the formation of a stable transfer layer, and the reduction in direct asperity contact at the sliding interfaces. However, reinforcement pull-out aggravates abrasive wear and leads to a higher specific wear rate for TNi10SiC composite. This work provides valuable information for advancing Ti6Al4V-based composites for enhanced structural and wear-resistant applications.

While IN738 Ni-based superalloy is a high strength alloy, it is feasible to improve its properties at the bulk level by reinforcing with graphene nanoplatelets (GNPs), taking advantage of the superior mechanical, tribological and thermal properties using the spark plasma sintering technique. In the present study, the influence of spark plasma sintering temperature range between 900 and 1100 degrees C on the microstructure, mechanical, tribolog-ical and thermophysical properties of GNPs/IN738 composite is assessed. The dispersion of GNPs reinforcement and alloying metals to form composite powder is conducted using a turbular mixer and low-frequency planetary ball milling, followed by spark plasma sin-tering. The relative density of the sintered samples assessed following Archimedes' method indicates increasing densification with the increasing sintering temperature from 94.7% (900 degrees C) to 98.5% (1100 degrees C). The microstructure assessed via SEM, XRD and Raman spectroscopy indicates the formation of precipitate gamma, intermetallic gamma prime, solid solution and GNPs strengthening phases. Thus, the mechanical (micro/nano hardness and Young's modulus), tribological (wear rate and coefficient of friction), and thermo-physical (thermal diffusivity, thermal conductivity, and specific heat capacity) properties increased with the increasing sintering temperature. The microhardness increased from 354HV (900 degrees C) to 469HV (1100 degrees C), nanohardness from 8 GPa (900 degrees C) to 17 GPa (900 degrees C), and Young's modulus from 190 GPa (900 degrees C) to 291 GPa (1100 degrees C). The wear rate reduced with an increase in sintering temperature for the three loads of 5, 10 and 20N. The thermophysical properties assessed from 25 to 600 degrees C show the formation of few inflection points as the temperature increases, which is attributed to the dissolution and rearrangement of pre-cipitate gamma prime and Cr in solid solution phases. Similarly, the small increment in the thermal diffusivity is equally associated with the smoother phonon transition at the GNPs/ matrix interface.(c) 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Aluminium 7075 (AA7075) is a desirable grade of aluminium alloy highly sought after for its high strength-to -weight ratio. In this study, AA7075/Fe1.2CrZnCuAlTi0.8 (HEA) composites were prepared by microwave sinter-ing, and a response surface methodology (RSM) was employed in the experimental design and analysis of the results. The variable input factors for a constant dwell time of 20 min are HEA dosage (5 wt%, 10 wt%, and 15 wt %), compaction pressure (20 MPa, 60 MPa, and 100 MPa), and sintering temperature (300 degrees C, 450 degrees C, and 600 degrees C). The properties examined were tensile strength, elastic modulus, elongation, microhardness, flexural strength, and impact strength. The outcome showed that 5 wt%, 10 wt%, and 15 wt% played an important role in the microstructural evolution of the composites for all temperature ranges. The XRD analysis detects the presence of alpha-aluminium, BCC phase, MgZn2, Al7Cu2Fe, and Al9Co2 phases as the sintering temperature increases. ANOVA results indicated that the input factors and their interactions played a major role in the responses. The surface plots revealed that 5 wt% - 10 wt% HEA reinforcement and 300 degrees C-450 degrees C sintering temperature improved the responses, whereas 10 wt% - 15% and 450 degrees C-600 degrees C were detrimental to the properties of the sintered com-posites. 20 MPa-100 MPa displayed favourable contribution on all response parameters. From the analysis, the optimum input combinations for achieving the desired strength enhancement in Fe1.2NiCrCoAlTi0.8 particles (HEAp) reinforced AA7075 alloy are 11.7% HEA, 75.2 MPa pressure, and 447.7 degrees C sintering temperature.

With the continent of Africa occupying the front seat of underdevelopment in the world, and its population increasing exponentially, there is an urgent need to come up with strategies to tackle the underdevelopment ravaging the continent and the demand posed by its constantly growing population. Engineering through appropriate engineering education is the answer to these challenges. In this review article, some of the challenges facing engineering education in sub-Saharan Africa such as responsiveness and relevance in the design of the undergraduate curriculum, shortage in the engineering capacity, etc. were studied. The factors that influence engineering education, in general, were also discussed and the strategies that are required for producing engineering graduates capable of taking up the challenges facing the 21st century engineers in the region were highlighted. Lastly, the review presents a guide for future engineering education and recommendations on how to re-engineer engineering education in sub-Saharan Africa to produce engineering graduates who are qualified technically and otherwise.

Spark Plasma sintering is an excellent technique for developing ceramic-reinforced binary/ternary nickel and titanium metal matrix composites (MMCs). This review analyzes the mechanical properties, microstructure, and densification characteristics of SPS-produced composites. Introducing ceramic reinforcement such as carbides, oxides, nitrides, or borides enhances the mechanical characteristics and functionality of MMCs. The SPS method has advantages such as high heating rates, low processing durations, and relatively low sintering temperatures, all of which assist in reducing reactivity concerns and retaining the desirable properties of the matrix and reinforcing materials. The impact of different process parameters such as temperature, pressure, heating rate, and holding time on the final microstructure and densification of the composites was discussed in this review. Additionally, it examined how different types, contents, and particle sizes of reinforcement affected the mechanical qualities, including hardness, tensile strength, fracture toughness, and wear resistance. Furthermore, the production of secondary phases and the interfacial bonding between the matrix and reinforcements are explored because they significantly affect the mechanical performance and behavior of the composites. This work contributes to an extensive understanding of the SPS procedure for ceramic-reinforced nickel and titanium MMCs, offering insightful information on processing parameters that enhance production and modify the characteristics of these technologically advanced materials for many applications in the aerospace, automotive, and structural industries.

In the present study, nickel (Ni) and graphene nanoplatelets (GNPs) are considered as ideal reinforcements for Mg-9Al-1Zn (AZ91D) magnesium alloy to form metal matrix composites (MMCs) because of their excellent mechanical properties. It is essential to utilize effective manufacturing techniques to develop AZ91D magnesium (Mg) alloy-nickel-graphene nanoplatelets (AZ91Z-Ni-GNPs) MMCs. Hence, the spark plasma sintering method is used to fabricate AZ91D-Ni-GNPs composites. HRTEM, OM, SEM, EDS, XRD, and Raman spectroscopy were used to investigate the microstructure, crystallinity, and elemental composition of both the blended powder and the sintered composites. GNPs and Ni were well-dispersed in the AZ91D Mg matrix, and effective interfacial bonding is formed between GNPs, Ni, and Mg alloy matrix powder before sintering. A Response Surface Methodology (RSM) with a central composite design was used to design the experiments by considering two variables, i.e., sintering temperature and pressure. The method was adopted to eliminate the trial-by-error approach. Using the data generated, quadratic regression models were developed for the relative density (g/cm 3 ), and Vickers hardness (HV) of the MMCs, and the parametric effects were explained via RSM. The process parameters were optimized, and the effective interaction between two descriptive variables (process parameters) on the relative density, hardness, and microstructural properties of Mg-based composites was investigated. Validation of the experimental run was performed using optimal process parameters acquired from the analyses to demonstrate the enhancement in the properties of the sintered composites. It was observed that the sintering temperature had a major influence on the relative density and hardness properties (responses). The optimal relative density and hardness obtained for AZ91D-Ni-GNPs composites were 1.723 g/cm 3 and 93.21 HV, respectively. The addition of GNPs to AZ91D-Ni produced material with improved properties.

Ni-Cr-ZrO2 composites with varying amounts of ZrO2 additive (5 wt%, 7.5 wt%, 10 wt% and 12.5 wt%) were fabricated using spark plasma sintering method at a sintering temperature of 1000°C, heating rate of 100°C/min, holding time of 5 min, and a pressure of 50 MPa. The effect of ZrO2 addition on the microstructure, tribological and mechanical properties of the developed composites were studied. The results showed that maximum densification was attained at 10 wt% ZrO2. Further increase in the fractions of ZrO2 within the composites results in a decrease in the relative density of the sintered composite. A significant increase in hardness from 433.24 HV to 510.11 HV and elastic modulus from 252.67 GPa to 294.6 GPa was observed in the fabricated samples as the ZrO2 content increase from 5 to 12.5 wt%. An appreciable improvement in the wear performance of the sintered samples was obtained with increasing ZrO2 content. The observed improvement in the properties of the sintered composites was attributed to the presence of the hard dispersoids of ZrO2 and formation of solid solution strengthening and hard Cr3Ni2 phases within the matrix of the sintered composites.

Ni-Cr-ZrO 2 composites with varying amounts of ZrO 2 additive (5 wt%, 7.5 wt%, 10 wt% and 12.5 wt%) were fabricated using spark plasma sintering method at a sintering temperature of 1000°C, heating rate of 100°C/min, holding time of 5 min, and a pressure of 50 MPa. The effect of ZrO 2 addition on the microstructure, tribological and mechanical properties of the developed composites were studied. The results showed that maximum densification was attained at 10 wt% ZrO 2 . Further increase in the fractions of ZrO 2 within the composites results in a decrease in the relative density of the sintered composite. A significant increase in hardness from 433.24 HV to 510.11 HV and elastic modulus from 252.67 GPa to 294.6 GPa was observed in the fabricated samples as the ZrO 2 content increase from 5 to 12.5 wt%. An appreciable improvement in the wear performance of the sintered samples was obtained with increasing ZrO 2 content. The observed improvement in the properties of the sintered composites was attributed to the presence of the hard dispersoids of ZrO 2 and formation of solid solution strengthening and hard Cr 3 Ni 2 phases within the matrix of the sintered composites. Keywords sintering , Ni-Cr-ZrO , composites , microstructure , nanoindentation hardness , wear

Environmental conservation and waste control have informed and encouraged the use of biodegradable polymeric materials over synthetic non-biodegradable materials. It has been recognized that nano-sized biodegradable materials possess relatively good properties as compared to conventional micron-sized materials. However, the strength characteristics of these materials are inferior to fossil-based non-biodegradable materials. In this study, biodegradable polylactide (PLA), reinforced with treated coconut husk particulates (CCP) for improved mechanical properties, was fabricated using an electrospinning process and representative volume element (RVE) technique, and some of the obtained mechanical properties were compared. It was observed that the electrospun CCP-PLA nanofibre composites show improved mechanical properties, and some of these mechanical properties using both techniques compared favourably well. The electrospun fibres demonstrate superior properties, mostly at 4 wt.% reinforcement. Thus, achieving good mechanical properties utilising agro waste as reinforcement in PLA to manufacture nanocomposite materials by electrospinning method is feasible and provides insight into the development of biodegradable nanocomposite materials.

Additive manufacturing (AM) of polymer-based composites in the automotive industry has enjoyed tremendous progress in recent times. The use of this manufacturing technique has made it possible for the manufacturing of cost-effective, single, complex and customized automotive components. Of all the available additive manufacturing techniques, stereolithography (SLA), selective laser sintering (SLS), fused deposition modelling (FDM), laminated object manufacturing (LOM) and inkjet are the most used in the creation of polymer composite parts in the automotive industry. In spite of the success recorded in the use of AM of polymer composites in the automotive industry, the technology is limited by the size and quantity of parts produced as some of the components are massive in size and often requires mass production. Hence, AM should be a complement and not a replacement to traditional manufacturing methods in the automotive industry. In this review, the progress made and some of the challenges that are associated with the use of AM of polymer-based composites in the automotive industry are presented.