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Research attention in powder metallurgy (PM) processing of high-entropy alloys (HEAs) is rising. Some reviews have been published but a detailed historical analysis to identify the thematic research areas and prospective future research areas is lacking. Therefore, this study presents a bibliometric literature analysis of PM-processed HEAs by mapping and clustering 700 articles published between 2007 and August 2022 in the Scopus database. The most prolific authors, their collaborators, institutions, and most preferred journals publishing PM-HEA works are identified and mapped. Publication trend shows that significant research attention in the PM processing of HEAs began to gain traction in 2016. The top three journals in this field are Journal of Alloys and Compounds, Materials Science and Engineering A, and Intermetallics. However, co-authorship network analysis does not reveal significant inter-institutional research collaboration indicating that strengthening this area could help to accelerate scientific discovery, enhance technology transfer, and commercialization of HEA products. Based on the co-occurrence frequencies of author keywords, popular research directions are identified, and a systematic review of emerging functional applications is undertaken. This work provides a comprehensive visual reference guide for researchers to deepen their knowledge of this field and delivers insight into prospective future research opportunities to stimulate further ground-breaking works.

Investigation on the hot deformability and workability of stir cast 6 wt.% steel particles reinforced aluminium 6063 matrix composites was undertaken in this study. Flow stress – strain curves generated from hot compression tests performed at strain rates of 0.01, 0.1, 1, and 10 s−1, and temperatures between 200–400°C, were used to study the flow behavior of the composite, while processing map developed from analyses of the deformation data, was used to establish the deformation mechanisms and processing safe zones for effective workability. Flow stress oscillations were observed to be prevalent at lower deformation temperatures and strain rates; largely due to the settling of reinforcement particles at grain boundary vicinities, rather than a homogeneous distribution. Also, the flow behaviour was largely strain rate insensitive. The dominant flow mechanism based on the flow stress patterns, processing map and microstructural validation was established to be dynamic recovery. Safe regions for processing based on Murty's and Gegel's criteria established the safe processing zones to be ~270–400°C at 0.01–1.0 s−1 and 380–400°C at 10 s−1. Deformation processing was unsafe at 200–260°C at 0.01–1.0 s−1 and between 200–380°C at 1.0–10 s−1.

Thermo-mechanical processing of refractory high entropy alloys (RHEAs) at high temperatures is very important. It is an effective method of modifying the microstructure, properties, and shaping into final components after casting. Using the Scopus database, 57 articles relating to the hot deformation of refractory high entropy alloys were extracted from 2011 to 2022. Despite the limited number of articles on hot deformation of RHEAs, it is important to find out if the dominant softening mechanisms reported in other metallic alloys are evident. This is the main impetus for this study since the hot deformation behavior has not been comprehensively studied. All the probable mechanisms influencing deformation in metallic alloys, such as work hardening, dynamic recrystallization, and dynamic recovery, have also been observed in RHEAs. The bulging phenomenon, serrated grain boundaries, and necklace-like structures reported in metallic alloys have also been detected in hot deformed RHEAs. Unsafe deformation behavior such as cracks that have been reported in metallic alloys, have also been observed in RHEAs. This review has provided a comprehensive study on the hot working processes of RHEAs and highlighted critical gaps for future research direction with some suggested limitations.

Additive manufacturing (AM) technologies and advances made globally in medicine, construction, aerospace, and energy sectors are discussed. The paper further explores the current state of AM innovation and development landscape in Africa as a late comer to this area of smart manufacturing. Peer-reviewed and published literature were retrieved from Scopus database from 2005 to 2021 and analysed. In Africa, out of 500 published articles, South Africa has the highest research throughput, whereas about two-thirds of the continent is not actively participating in this burgeoning field. The main AM techniques most widely used are selective laser melting, fused deposition modelling, and direct energy deposition. Globally, there is an interplay of computational (machine learning and mechanistic models) and experimental approaches to understanding the physical metallurgy of AM techniques and processes. Though this trend is consistent with global practices, Africa lags the world in AM technologies, a niche that could leapfrog the manufacturing sector. Thus, Africa need to foster collaborative partnership within and globally to become an active global player in this industry.

The structural characteristics, mechanical and damping properties of stir-cast Al-10 wt.% Zn based composites developed using 6 and 8 wt.% Cu, and 8 wt.% SiC particles as reinforcements, were investigated. The low porosity (

In this study, we show that optimising cutting forces as a machining response gave the most favourable conditions for turning of Ti-6Al-4V alloy. Using a combination of computational methods involving DEFORM simulations, Taguchi Design of Experiment (DOE) and analysis of variance (ANOVA), it was possible to minimise typical machining response such as the cutting force, cutting power and chip-tool interface temperature. The turning parameters that were varied in this study include cutting speed, depth of cut and feed rate. The optimum turning parameter combinations that would minimise the machining responses were established by using the “smaller the better” criterion and selecting the highest value of Signal to Noise Ratio. Confirmatory simulation revealed that using cutting speed of 120 m/min, 0.25 mm depth of cut and 0.1 mm/rev feed rate, the lowest cutting force of 88.21 N and chip-tool interface temperature of 387.24 °C can be obtained. Regression analysis indicated that the highest correlation coefficient of 0.97 was obtained between cutting forces and the turning parameters. The relationship between cutting forces and the turning parameters was linear since first-order regression model was sufficient.

The response of two different types of aluminium matrix composites (AMCs) reinforced with silicon carbide ceramic particulates or nickel metallic particulates to hot compression testing parameters was evaluated. The composites were produced via two-step stir-casting technique. Axisymmetric compression testing was performed on the samples at different deformation temperatures of 220 and 370 °Ϲ, 0.5 and 5 s−1 strain rates and total strains of 0.6 and 1.2. The initial and post-deformed microstructures were studied using optical and scanning electron microscopy. The results show that flow stress was significantly influenced by imposed deformation parameters and the type of reinforcements used in the AMCs. Nickel particulate reinforced aluminium matrix composite (AMC) showed superior resistance to deformation in comparison with silicon carbide reinforced AMC under the different testing conditions. In both AMCs, work hardening, dynamic recovery and dynamic recrystallisation influenced their response to imposed parameters. The signature of dynamic recrystallisation was very apparent in aluminium matrix composite reinforced with nickel particulates.

An overview of welding methods and process parameters and its effects on mechanical behaviour and structural integrity of magnesium and its alloys are discussed. These alloys are less dense and beneficial structural alloys for improved energy efficiency, eco-friendliness and driver of circular economic model for sustainable design and innovative ecosystem. While the application of Mg-alloys is projected to increase, understanding the mechanical behaviour and structural integrity of welded joints are critical. Thus, fusion and solid-state welding processes of these alloys are discussed with emphasis on mechanical characterization. Laser welding is the most effective fusion welding technique for most Mg alloys whereas, the predominant solid-state method is friction stir welding. The importance of process variables such as heat inputs, welding velocity (speed) and post weld treatments on the microstructural evolution, on mechanical and physical properties of the distinct zones of the weld joints are described. The weldment is the most susceptible to failure due to phase transformation, defects such as microporosity and relatively coarse grain sizes after solidification. The implication of the design of quality weld joints of Mg alloys are explored with areas for future research directions briefly discussed.

Machining is one of the major contributors to the high cost of titanium-based components. This is as a result of severe tool wear and high volume of waste generated from the workpiece. Research efforts seeking to reduce the cost of titanium alloys have explored the possibility of either eliminating machining as a processing step or optimising parameters for machining titanium alloys. Since the former is still at the infant stage, this article provides a review on the common machining techniques that were used for processing titanium-based components. These techniques are classified into two major categories based on the type of contact between the titanium workpiece and the tool. The two categories were dubbed conventional and non-conventional machining techniques. Most of the parameters that are associated with these techniques and their corresponding machinability indicators were presented. The common machinability indicators that are covered in this review include surface roughness, cutting forces, tool wear rate, chip formation and material removal rate. However, surface roughness, tool wear rate and metal removal rate were emphasised. The critical or optimum combination of parameters for achieving improved machinability was also highlighted. Some recommendations on future research directions are made.

Isothermal compression testing of BLA-SIC hybrid reinforced Aluminium composites was performed on Gleeble 3500 thermomechanical simulator under different deformation temperatures (300–400 °C) and strain rates (0.01–1 s‑1). The flow behaviour and the softening mechanisms were established using the trend of the stress-strain curves, activation energy and microstructural examination. The results showed that flow stress increased with decreasing temperature; but was not entirely strain rate sensitive − a characteristic identified in some Al 6XXX based metallic systems. Also, uncharacteristic flow stress oscillations were observed at strain rates of 0.01 and 0.1 s‑1 while steady state flow stress was observed at 1 s‑1. The hot working activation energy was ∼290.5 kJ/mol which was intermediate to the range of 111–509 kJ/mol reported in literature for various Al based composites. It was proposed that at strain rates of 0.01 and 0.1 s‑1, dynamic recrystallization and/or dislocations-reinforcements interactions were the dominant deformation mechanism(s), while at 1 s‑1, dynamic recovery was predominant.

The microstructural characteristics, mechanical and damping properties of AleZn based composites reinforced with 6, 8, and 10 wt% martensitic stainless steel (SS) and 10 wt% silicon carbide (SiC) were investigated. The composites were produced via double stir casting process, and structural assessment was undertaken with the use of scanning electron microscopy (SEM) and X-ray diffraction analysis. The mechanical properties (hardness and tensile properties) and damping behaviour were also evaluated. The microstructures showed well delineated particles varied particle size and dispersion patterns, while the XRD results indicated marginal presence of reaction induced intermetallic phases. Relative to the unreinforced AleZn alloy, the hardness, ultimate tensile strength (UTS), specific strength improved with increase in SS wt. % (18%, 26%, 44% for hardness; 33%, 40%, 51% for UTS; and 19%, 28%, 47% for specific strength, for 6, 8, and 10 wt% SS particles, respectively). Also, all the AleZn/SS composite grades had strength and ductility characteristics superior to that of the AleZn/SiC composite. Particle and interface strengthening, was linked to the improved strength offered by these grades of composites, while more uniform strain distribution due to the inherent ductile and deformable nature of the SS particles, attested to by the relatively higher signs of dimple fractures; was linked to the superior ductility. The damping capacities of all the AleZn based composites were higher than that of the unreinforced AleZn alloy, with the inherent damping capacities of constituents, constituent weight proportions, particle/interface mobility sensitivity to temperature, and dislocation damping effects, linked to the variations in damping behaviour exhibited by the AleZn based composites. [ABSTRACT FROM AUTHOR]

The technological advancement of drones benefited the mining industry and positively transformed operations by providing real-time data. This allows for the identification and mitigation of mining hazards as they emerge, rapid collection of data in risky locations and the ability to share accurate maps and models with shareholders. In order to better understand how drones can serve the mining industry in the most beneficial way, this review discusses the major milestones in history that gave rise to the invention of the modern drones. Furthermore, the current applications and future potential of drones in the mining industry are discussed. [ABSTRACT FROM AUTHOR]

Purpose: A review of readily available quantitative environmental data was conducted in order to determine the state of sustainability reporting and identify possible future research areas in Portugal.Methods: Internet searches of articles written in English and published between 2001 and 2015 were conducted using the keywords “life-cycle assessment,” “LCA,” “water footprint,” “carbon footprint,” and “Portugal.” Additionally, reports from the Global Reporting Initiative (2015 only) were included in the search.Results and discussion: It was found that 79% of reports found were published in the period 2011-2015. Several reports were found for the forestry, paper and pulp, food and beverage, energy and electricity, waste management, and automotive industries, while no reports were found for the textile, footwear and clothing, and base metal and mineral industries. As such, these are industries on which future studies might focus. No reports found were published by governmental organizations, although it is thought that expanding the search to include Portuguese language results would yields more results. The majority (68%) of companies reporting to the GRI adhered to the relevant guidelines.Conclusions: A total of 72 reports were found (41 LCAs, water- or carbon footprints, and 31 GRI reports). It is unclear if there are other reports that may be restricted to “hidden” datasets or company specific archives. The aim of this report was to highlight those that were available to a non-specialist or international audiences trying to gain a greater understanding of the LCA space in Portugal. [ABSTRACT FROM AUTHOR]