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The hydrogen evolution reaction (HER) based on water electrolysis represents an ideal approach for hydrogen production. The advancement of highly active non-precious metal catalysts holds paramount importance. This research employed powder metallurgy sintering to prepare Ni–Cr–Fe and Ni–Cr–Fe–Mo porous materials. It investigated the impact of Mo doping and sintering temperature on the catalytic activity and microstructural influence of hydrogen evolution materials. Furthermore, the materials' electrochemical performance and long-term stability in 6 mol/L KOH were examined. In complicated systems, the current work provides a feasible method for producing hydrogen from Ni–Cr–Fe–Mo porous materials in a strong alkali environment. The results exhibited that when Mo content is 5% and the sintering temperature is 800 °C, the porosity of Ni–Cr–Fe–Mo porous materials is up to 39.9% and the catalytic activity is up to 97%. At the same time, the current density decays to 7.1% after 1000 cycles of electrolysis and shows good HER stability after 48 h. The enhanced catalytic activity for hydrogen evolution emanated from the positive synergy among the transition metal elements. • The porous Ni–Cr–Fe–Mo cathodes were sintered through powder metallurgy. • Ni–Cr–Fe–Mo powder provides more active sites and increases the HER performance of the material. • The cathodes exhibited excellent HER activity and stability in 6 mol/L KOH. [ABSTRACT FROM AUTHOR]

The study addresses the requirement for better machining of titanium alloy (Ti–6Al–4V) in Electrical Discharge Machining (EDM) with a Cu–TiB 2 ceramic composite powder metallurgy electrode. The electrode underwent analysis for relative density, hardness, and microstructure using field emission scanning electron microscopy and X-ray diffraction. Results indicated a relative density of approximately 90.08%, a microhardness of around 142 H V, and an electrical conductivity of 46% IACS. Response Surface Methodology (RSM) was used as Design of Experiment (DoE) technique for this study to investigate the effects of pulse current (Ip), pulse on time (Ton), and discharge voltage (V) on Material Removal Rate (MRR) and Surface Roughness (SR). Analysis of variance (ANNOVA) at a 5% significance level highlights the significant impact of Ip, Ton & V, and the interaction between selected parameter on MRR and SR. Results show a significant influence of pulse current (Ip) and pulse duration (Ton) on both MRR and SR. Rising pulse current correlates with improved MRR, with optimal parameters identified as a pulse current of 15 A, a pulse on time of 150 μs, and a voltage of 50 V. The study also looks into the usage of reverse polarity to improve surface finish compared to typical EDM methods. The use of Scanning Electron Microscope (SEM) and Energy Dispersive Spectroscopy (EDS) analyses adds depth to the evaluation of surface formations on the workpiece. EDS analysis indicates the presence of 63.13 wt (%) of boron on the machined work surface, affirming the effectiveness of the developed Cu–TiB 2 electrode in machining titanium alloy. [ABSTRACT FROM AUTHOR]

A significant and increasing number of studies have been dedicated to complex concentrated alloys (CCAs) due to the improved properties that these metallic materials can exhibit. However, while most of these studies employ melting techniques, only a few explore powder metallurgy and pressureless sintering as production methods. In this work, a microstructural characterization of AlCrCuFeMnNi CCA samples obtained by powder metallurgy and pressureless sintering using mixtures of powders with different compositions was carried out. One batch of samples (B1) was prepared using commercial powders of Al, Cr, Cu, Fe, Mn, and Ni. Another batch (B2) used mixtures of CrFeMn, AlNi, and Cu powders. A third set of samples (B3) was obtained by adding 1% at. of Mg to the B2 powder. The samples were characterized by X-ray diffraction, scanning and transmission electron microscopy, energy dispersive spectroscopy, density measurements, and hardness tests. Thermodynamic calculations were also used to complement the microstructural characterization. All the obtained samples exhibited high relative density and hardness values. However, B3 samples showed a higher hardness, attributed to the finer distribution of oxide particles, which was promoted by the presence of Mg during sintering. These last samples presented a hardness/density ratio of 62 HV/(g cm−3), surpassing that of some martensitic stainless steels and nickel–titanium alloys. [ABSTRACT FROM AUTHOR]

Sintered gears manufactured through powder metallurgy technology contain residual porosity that can make them inadequate for high power supply. Crack propagation is significantly enhanced by both residual porosity and cyclical stresses involving the teeth. The use of densification processes can highly improve their performances, permitting the reduction of the residual porosity. Among the densification processes, the rolling assumes a key-role. The process permits the densification of the tooth flanks, the most stressed parts of the wheel. However, the performances of the rolled wheel depend on several process parameters, whose setup phase requires several efforts and many experiments. Finite element (FE) model can be a helpful tool, allowing a faster estimation of the process parameters, reducing waste and costs linked to the experimental tests. In this sense, FE modelling techniques discussed in literature only cover the simulation of spur gears densification process, since they consist of in-plane 2D finite elements. In this paper, different numerical modelling techniques, based on 2D finite elements, are proposed to simulate the densification process of spur gears and used to perform a tendency analysis to explore the effects of wheelbase reduction between the forming rollers on the material densification. Material densification appeared higher for reduced wheelbases, but an increasing cavity was observed at the tooth root as the wheelbases decreases. Moreover, a FE model based on 3D finite elements is proposed to reproduce numerically the rolling process of a helical gear. The accuracy of the 3D FE model was measured against the results provided by some experimental tests, herein discussed too. A good agreement between numerical and experimental results was observed. [ABSTRACT FROM AUTHOR]

Recently, high-temperature composites reinforced with in-situ phases have been developed as a new class of composites for harsh environments. The behaviour of these composites under sudden heating and cooling conditions is greatly influenced by the type and fraction of components. The aim of this study is to investigate the microstructural properties and mechanical response of iron based composites after thermal shock cycling. The fabrication process involved in-situ powder metallurgy (IPM) sintering of Fe–B 4 C starting powders. The samples were subjected to thermal shock with a constant temperature differences (ΔT: 600 °C) and varied cycles (N: 1–50). Comparison of microstructural changes and mechanical behaviour before and after thermal shock has been carried out. The boron atoms released from the initial B 4 C generated diffusion zones in the matrix dominated by iron boride phases (Fe 2 B/FeB). An effective matrix-reinforcement interface has been created by in-situ powder metallurgy, where boride phases are almost homogeneously distributed in the iron matrix. While the hardness of the composites was significantly developed by the Fe 2 B/FeB phases, the addition of B 4 C resulted in a reduction in the coefficient of thermal expansion (CTE). The in-situ phases contributed in the minimisation of the coefficient mismatch by balancing the thermal expansion coefficients between iron and the initial B 4 C. Under the influence of thermal shock, microcracks and then macrocracks formed on the sample surfaces, increasing in width and depth with thermal cycles. This resulted in accelerated fracture damage under post-thermal loading. Both the impact and flexural strengths of the samples were significantly reduced as the number of thermal cycles increased. Although the 20% B 4 C reinforced composite provided maximum hardness, it showed poor resistance to thermal loading. The best results for mechanical loads were achieved by the 5% B 4 C reinforced composite, which showed no cracks even after 50 thermal cycling. [ABSTRACT FROM AUTHOR]

Metal Matrix Composites (MMCs) have recently been preferred over traditional materials in many engineering applications. Titanium matrix composites (TMCs) are used in the automotive, aerospace and defence industries thanks to their exceptional strength, high fatigue strength, good corrosion resistance and high elastic modulus. Some of the most used reinforcement materials for TMCs are SiC, Zr 2 O 3 , Al 2 O 3 , graphene, carbon nanotube (CNT) and TiC. In this study, TMCs reinforced Al 2 O 3 were produced via conventional powder metallurgy (PM) and ultrasonic-assisted mixing. An Al 2 O 3 in varying amounts (5 and 10 wt%) was incorporated into the TMCs via mechanical alloying (MA) for 5 h in a high-energy ball mill and using different process control agents (PCA, Stearic acid (SA), Polyvinyl Alcohol (PVA), Ethanol). The mechanically alloyed (MA'ed) powders were compacted by a hydraulic press under uniaxial pressure of 450 MPa and sintered at 1200 °C for 2 h in an argon atmosphere. The microstructural, mechanical and tribological properties of Ti-xAl 2 O 3 powders and bulk samples were investigated. The highest hardness and the lowest specific wear rate were found in specimens reinforced with 5 wt% Al 2 O 3 , using ethanol as PCA, and produced by ultrasonic-assisted mixing, but the same specimen had the lowest compressive strength. [ABSTRACT FROM AUTHOR]

Decreasing the sheath stresses and facilitating osteogenesis are of great interest in the preparation of orthopedic implants. For this reason, the fabrication of porous composite samples based on Ti alloys is of great importance in the medical industry. This research is dedicated to investigating the mechanical and biological properties of porous composite samples prepared by powder metallurgy, space holder technique, and sintering using Spark Plasma Sintering (SPS). According to the results obtained, it was found that owing to an increase in the volume percentage of the space holder, the density of the samples decreased while the true porosity percentage of the samples increased. The morphology of the pores formed in the structure was spherical with a uniform distribution. In addition, it was found that the elastic modulus of the sample decreased significantly so that the samples containing >30 vol% cenosphere space holder exhibited properties similar to those of bones. Also, according to the results of the MTT, SBF immersion, and cell adhesion tests, it was concluded that the samples were of high cell viability. Moreover, the growth and proliferation of bone cells and the formation of apatite crystals using these composites were confirmed. [Display omitted] • Spherical shape and maintain a consistent distribution of the fabricated cavities. • The percentage of cell viability in this composite alloy was estimated to be over 90%. • Achieving bone-like properties in Ti–15%Mo-30 vol% Cen composite alloy samples. • A reduction in the elastic modulus of the prepared composite alloys. [ABSTRACT FROM AUTHOR]

In this study, Si3N4 (1-12% by weight) and graphene (0.15-0.45% by weight) reinforced Al6061 matrix composites were produced by the induction heat treatment and powder metallurgy methods. The density, hardness, compressive strength, wear rate, microstructure, and phase structure of the produced composite materials were investigated, respectively. As a result of the tests performed, the densest microstructure, and the best mechanical/tribological properties were obtained in Al6061-9%Si3N4-0.15%graphene composite structure. As a result of the heat treatment studies, it was determined that the mechanical and tribological properties of the induction hot pressed samples after the sintering process improved by ~15% compared to only sintered samples. [ABSTRACT FROM AUTHOR]

Aluminum matrix composites (AMCs), incorporating Zirconium Nitride (ZrN) as reinforcing additives, demonstrate immense promise for applications in aerospace, automotive, and power generation due to their unique combination of low density, superior mechanical properties, and excellent thermal/electrical conductivity. This study explores the influence of ZrN reinforcement on the microstructure and mechanical properties of AlSi10Mg metal-matrix composites. Utilizing high-energy ball milling (HEBM) and spark-plasma sintering (SPS), ZrN/AlSi10Mg composites were synthesized, achieving nearly full density with uniform ZrN distribution, while phase and chemical transformations were not observed in the bulk composites. The addition of ZrN resulted in a notable increase in hardness of 237% (182 ± 8 HV2), elastic modulus of 56% (114 ± 3 GPa), compressive and tensile strength of 183% (565 ± 15 GPa), and 125% (387 ± 9 GPa), respectively, for composites containing 30% ZrN, compared to the non-reinforced alloy. Experimentally determined coefficients of thermal expansion (CTEs) for composites with 10%, 20%, and 30% ZrN content were 19.8 × 10−6 °C−1, 19.1 × 10−6 °C−1, and 18 × 10−6 °C−1, respectively, which well relates to Schapery’s model. These findings contribute to understanding the synthesis, mechanical behavior, and thermal properties of ZrN/AlSi10Mg composites, demonstrating their potential for diverse engineering applications. [ABSTRACT FROM AUTHOR]

The development of water electrolysis hydrogen production technology is of great significance for accelerating the global carbon neutrality goals. Nickel-based electrode materials are considered the most promising catalysts for alkaline water electrolysis. However, the slow kinetics of the hydrogen evolution reaction remains a key challenge to be solved. To address this, a porous Ni–Cu–Ti/NCNTs cathode electrode was prepared using the powder metallurgy method. The microstructure characterizations and electrochemical measurements revealed that adjusting the content of NCNTs, while maintaining the Ni–Cu–Ti ratio of 5.5:3.5:1, can improve the catalytic activity of hydrogen evolution to a certain extent. Among the electrodes tested at room temperature, the one with 0.7% NCNT content exhibited the best performance in terms of hydrogen evolution. The analysis suggests that the porous structure of the electrode provides ample channels for object transmission. The addition of NCNTs further enhances the surface roughness of the electrode, exposing more active sites. Additionally, NCNTs promote electron transfer, synergize with Ni, Cu, and Ti, and improve the catalytic activity of hydrogen evolution. • The porous Ni–Cu–Ti/NCNTs cathodes were sintered through powder metallurgy. • NCNTs powder provides more active sites and increases the HER performance of the material. • The cathodes exhibited excellent HER activity and stability in 6 M KOH. [ABSTRACT FROM AUTHOR]

Due to the excellent activity and stability of MnCo 2 O 4 toward the oxygen evolution reaction (OER) in acidic solution, a Pb–MnCo 2 O 4 composite anode for zinc electrowinning was prepared by embedding dispersed MnCo 2 O 4 particles into a Pb matrix in a powder metallurgy process. In this work, the phase structure, chemical composition, and morphology of the oxide layers formed on Pure-Pb and Pb–MnCo 2 O 4 were analyzed by XRD, SEM, and EDS. Galvanostatic polorization, Tafel tests, and EIS measurements were performed to investigate the anodic potential variation and OER kinetics of the Pure-Pb and Pb–MnCo 2 O 4 composite anodes. Compared with that on the Pure-Pb anode, the oxide layer on Pb–MnCo 2 O 4 is thinner, more compact, and more stable in a 160 g L−1 H 2 SO 4 solution containing 4 g L−1 Mn2+. Consequently, the Pb–MnCo 2 O 4 composite anode exhibited a much lower anode slime production (8.7 mg) during 72 h of the simulated zinc electrowinning process. Despite the smaller surface area and lower PbO 2 content of the oxide layer, the Pb–MnCo 2 O 4 composite anode presented preferable OER kinetics with a lower OER charge transfer resistance (0.729 Ω cm2) and a smaller Tafel slope (90.74 mV dec−1), which contributed to a 70 mV reduction in the anodic potential compared with that of the Pure-Pb anode. • The anodic potential of Pb–MnCo 2 O 4 composite anode is 70 mV than the Pure-Pb anode. • The oxide layer on Pb–MnCo 2 O 4 is thinner, more compact, and more stable. • Pb–MnCo 2 O 4 exhibits a smaller tafel slope and lower charge transfer resistance of OER. • The incorporation of MnCo 2 O 4 significantly reduces the production of anode slime. [ABSTRACT FROM AUTHOR]

Aluminum composites, reinforced with CNT and ZrO2 particles, were synthesized via powder metallurgy, undergoing mechanical testing and molecular dynamics (MD) simulations. Hybrid reinforcement significantly increased strength and hardness while preserving toughness through extrinsic toughening mechanisms, preventing a substantial drop in energy absorption. MD simulations revealed dislocation nucleation at reinforcement interfaces, enhancing material strength during propagation. Various reinforcements activated specific strengthening mechanisms, quantified by models. The hybrid composite exhibited excellent strength enhancement and maintained toughness up to a specific reinforcement content. Despite a reduction in energy absorption, the remarkable strength improvement suggests synergistic reinforcement effects, suitable for high-performance, lightweight materials. [ABSTRACT FROM AUTHOR]

This reports the tribological behavior of sintered aluminum composite with bio-oil as lubricant. The composite is fabricated by powder metallurgy route, and the aluminum is reinforced with the particles V2O5 and B4C. The bio-lubricant oil is Pongamia, Jatropha, and blended Pongamia with Jatropha of equal volume. The wear test was carried out at the sliding speed of 3m/s and load ranging up to 180 N, and the wear behavior of Al–xV2O5–2B4C composite. Then the composite’s friction coefficient and weight loss were tested on a pin-on-disc tribometer. Further, pinworn surfaces were analyzed by Scanning Electron Microscope. The mix of Pongamia with Jatropha of equal volume resulted in a good change in specific wear rate and coefficient of friction of composites. [ABSTRACT FROM AUTHOR]

Copper (Cu) is a ductile material with excellent electrical and thermal conductivity. It is widely used in many industries including automotive, electronics and electricity. However, the mechanical properties of copper are relatively poor. Graphene or graphene nanoplatelets (GNPs) have outstanding properties such as high strength, high young modulus, and large surface area. In this way, they significantly change the mechanical properties when used as reinforcement in metal matrix composites. In particular, in the field of powder metallurgy (PM), the properties of metallic matrix composites produced with these two materials are still under study. In the production of powdered metal components, the type of additive is important in terms of production cost. As the proportion of additives in the manufactured part increases, the production cost will increase accordingly. This study aims to determine which fabrication methods are used to obtain the highest mechanical properties values with the lowest amount of graphene contribution for Cu-GNP composites. The percentages of additives used in the studies are indicated together with the consolidation and mixing methods to prove the above-mentioned purpose. Thus, it has been determined by which production methods the studies with the highest percentage increase in mechanical properties were produced by using the optimum additive ratio for Cu-GNP metal matrix composites. In this regard, the highest hardness value was obtained with 118% increase percentage, by High pressure torsion method. In another study, Electro-co-deposition method were applied. As a result, the highest tensile strength value increased by 110%. The highest increase in yield strength value was obtained by Spark plasma sintering method with 239%. In addition, the effects of different additives were also examined. Other inferences from the studies are given in the result and discussion section. [ABSTRACT FROM AUTHOR]

When processed conventionally, aluminum-bronze alloys with high mechanical strength require machining after the raw state of fusion, and the waste (chips), if not reused, can cause problems for the environment and costs for the company. Therefore, this article proposes an alternative for recycling aluminum bronze through the new route via Powder Metallurgy (PM), analyzing the resulting microstructure. This study compares the microstructures of the aluminum bronze derived from extraction (the samples received - SR) and the state after the powder metallurgy (PM) process with the addition of vanadium carbides (VC). The study also analyzes the distribution of VC in the microstructure of the PM composite as well as the influence of the TQ30 heat treatment on this composite. For the PM process, aluminum alloy and bronze chips were ground together with vanadium carbide (VC) in a high-energy mill for 50 hours. The powders obtained were pressed uniaxially (400 MPa) to achieve good compaction. The samples were then sintered (900°C/1h), water quenched (900°C/2h), and subjected to treatment according to the TQ30 standard, which, in addition to the previous treatments, also includes tempering at 500°C for 2 hours (ASTM B150/B150M-12 standard). The microstructure observed in the SR samples was martensitic (in needles), with secondary phases dispersed in the matrix. On the other hand, the microstructure of the PM samples showed equiaxed grains of the alpha phase (κ), as well as the secondary phases kapa (κ) and beta line (β'), in contrast to the needle-shaped microstructure of the conventional melting process. [ABSTRACT FROM AUTHOR]

Binary Ti100-x–Cux (x = 1.6 and 3.0 wt.%) alloys were produced by the application of mechanical alloying and powder metallurgy processes. The influence of the copper concentration in titanium on the microstructure and properties of bulk alloys was investigated. The synthesized materials were characterized by an X-ray diffraction technique, scanning electron microscopy, and chemical composition determination. The electrochemical and corrosion properties were also investigated. Cold compaction and sintering reduced the content of α-Ti content in Ti98.4–Cu1.6 and Ti97–Cu3 alloys to 92.4% and 83.7%, respectively. Open Circuit Potential measurements showed a positive shift after the addition of copper, suggesting a potential deterioration in the corrosion resistance of the Ti–Cu alloys compared to pure Ti. Electrochemical Impedance Spectroscopy analysis revealed significant improvement in electrical conductivity after the addition of copper. Corrosion testing results demonstrated compromised corrosion resistance of Ti–Cu alloys compared to pure Ti. In summary, the comprehensive investigation of Ti100-x–Cux alloys provides valuable insights for potential applications in biosensing. [ABSTRACT FROM AUTHOR]

An influence of processing parameters including the effect of reinforcement particulates for HA-ZnO-Fe3O4 composites fabricated via powder metallurgy is reported in relation to the metallurgical and mechanical properties. The results depict the effectiveness of Fe3O4 over HA composite along with metallurgical aspects and its interface formation. The obtained results confirm an improvement of around 100% in compressive strength and around 40% reductions in the hardness value for adding 10% Fe3O4 in HA composite. Experimental analysis confirms that adding 10% Fe3O4 has resulted in 6.9 GPa of hardness and 50.1 MPa of compressive strength. A mathematical model (probability regression fit) is analyzed for the evaluation of the interaction effect between mechanical properties and processing parameters with the help of an analysis of variance (ANOVA) and analysis of covariance (ANCOVA). In summary, the model suggested that Fe3O4 is a dominating factor and responsible for the variation in mechanical properties in the composite. [ABSTRACT FROM AUTHOR]

In this work, CoCrFeMnNi high-entropy alloys (HEAs) were fabricated by mechanical alloying and hot-pressing-assisted powder metallurgy method. For HEA powders, the effect of milling time on the morphology, particle size, crystallite structure and oxidation resistance of the HEA particles was studied. For sintered HEAs, effects of milling time and hot-pressing on the microstructure evolution, density, hardness, friction coefficient, wear rate and surface roughness of CoCrFeMnNi HEAs were investigated. Milling the particles for 5 h resulted in further cold welding of the initial particles and the formation of many coarse and cold-welded particles. The particle-size distribution obtained after 5 h of milling was single peaked and had a relatively narrow distribution range. An increase in oxidation resistance with increasing milling time was observed due to the embedding of hard and highly oxidation-resistant particles such as Co, Cr and Ni into ductile Fe particles. The CoCrFeMnNi alloy produced with 5 h of milling and at 650 MPa pressure had the highest relative density with 86.29%, while the sample fabricated with 0.5 h of milling and 550 MPa pressure showed the lowest relative density with 77.34%. The lowest wear rate was obtained in the sample produced with 5 h of milling and at 650 MPa. At the same time, the lowest average coefficient of friction was obtained as approximately 0.28 for the sample produced under these conditions. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the mechanical and metallurgical properties of magnesium AZ91 composite. Zinc and Aluminium were selected as reinforcement particles in the Magnesium metal matrix composite. The composites 88.5%Mg-9%Al-1.5%Mn-1%Zn, 87.5%Mg-9%Al-2.5%Mn-1%Zn, 86.5%Mg-9%Al-3.5%Mn-1%Zn, 85.5Mg-9%Al-4.5%Mn-1%Zn, 84.5%Mg-9%Al-5.5%Mn-1%Zn and 83.5%Mg-9%Al-6.5%Mn-1%Zn are prepared through powder metallurgy. The hardness and compressive tests are used to investigate the mechanical properties of the magnesium composite. The results of the mechanical properties indicate that manganese plays a vital role in improving the hardness of the AZ91 composite. The thermogravimetric analysis investigated the weight ratio % at the 400OC. The scanning electron. microscopic analysis was used to investigate the reinforcement particle's bonding level and the defects on the composite. Based on the results, the manganese plays a vital role in improving the mechanical properties of the AZ91 composite. [ABSTRACT FROM AUTHOR]

Oxide dispersion strengthened (ODS) alloys, due to their high irradiation resistance and good mechanical properties at high temperatures, are promising for applications in Generation IV reactors, especially GFR, and fusion installations. However, the biggest challenge in applying ODS materials is related to fabrication techniques. This paper aims to evaluate powder metallurgy processing and the effect of small additions of oxide- and carbide-forming elements on the microstructure and mechanical properties of Fe–Cr–Al-based ODS alloys. The series of ODS alloys with Y2O3 and different additions of Ti and V was prepared by mechanical alloying (MA) and consolidated by spark plasma sintering (SPS), which is less often employed to fabricate ODS alloys than hot extrusion or hot isostatic pressing. The investigations were performed on MAed powders, bulk-sintered samples, and samples after homogenization annealing. The MAed powders reveal two body-centered cubic (bcc) alloyed phases with close lattice parameters. The sintered samples show a single bcc phase (a = 2.88–2.89 Å) matrix and a high-volume fraction of homogenously distributed nanometric oxide precipitates. The addition of vanadium and titanium leads to the formation of vanadium- and titanium-rich nanometric oxides and carbides. The bulk samples show fine grain and stable microstructure with an average grain size slightly below 1 µm. Moreover, after homogenization annealing and air cooling, the relative density slightly increases. Hardness after heat treatment is relatively stable, which was confirmed by nanoindentation and Vickers microhardness results. These experimental findings promise to develop Fe–Cr–Al-based ODS materials tailored for operation under harsh conditions in nuclear reactors. [ABSTRACT FROM AUTHOR]

Powder metallurgy (P/M) was utilized to produce copper (Cu) matrix composites reinforced with few-layered graphene (FLG), which was produced by electric arc discharge (EAD). The structural and mechanical properties of the composites were investigated depending on the milling time and the graphene content. It was determined in SEM and TEM analyses that FLG was uniformly dispersed in the Cu matrix. Compared to pure Cu, an increase in hardness of approximately 31.8% was provided for 0.3 wt% FLG/Cu composite sintered after 5h of milling. Furthermore, with the addition of FLG, a decrease was observed in the COF values of the composites obtained by 7h milling. Grain refinement is considered a relevant strengthening mechanism for FLG/Cu composites. [ABSTRACT FROM AUTHOR]

In this study, Al2024/TiB 2 composites with different TiB 2 fractions (5, 10 and 15 vol%) were fabricated by high-energy ball milling and spark plasma sintering. The effects of TiB 2 fraction on the microstructure, hardness and wear resistance of the composites were explored to determine the optimal TiB 2 content in the composite with optimal properties. An increase in Vickers hardness of the composites correlates with the increased TiB 2 content, and the Al2024-15TiB 2 composite exhibits the highest hardness. The wear rate of the composite initially increases and then decreases with higher TiB 2 content. Notably, the Al2024-10TiB 2 composite demonstrates the best wear resistance with a wear rate of 1.14 × 10−4 mm³/Nm, representing a 96.81 % reduction compared to the unreinforced Al2024. The deteriorated wear resistance of the Al2024-15TiB 2 composite was attributed to the decreased toughness and severe three-body abrasion caused by the excessive TiB 2 particles. [ABSTRACT FROM AUTHOR]

An efficient new thermal-wave inverse-problem approach based on an integral-equation boundary-value method coupled with an imperialist competitive algorithm was developed. The methodology was successfully applied to simultaneously reconstruct density and thermal conductivity depth profiles in a sintered powder metallurgy sample from an industrial automotive manufacturer with a surface layer of higher density than the bulk. The density and thermal conductivity depth profiles were validated independently using the manufacturer's data and in-house temperature and porosity measurements. The present non-destructive inverse problem approach represents a generalized formalism to thermal-wave reconstruction of dual depth profiles using frequency scan data measured from the interrogated surface. From a fundamental viewpoint, the method adds significant insights into the relationship between thermal conductivity and density distributions in inhomogeneous solids. [ABSTRACT FROM AUTHOR]

Bi 2 Te 3 -based crystal ingots produced by zone melting (ZM) are the most widely used materials to manufacture commercial thermoelectric (TE) devices. However, the poor mechanical properties of such crystalline materials limit the production of small-scale devices. While processability can be improved by powder metallurgy (PM), it also leads to the deterioration of the TE properties due to the donor-like effect of the introduced defects and grain boundaries. Thus, additional efforts towards re-optimizing doping are required. Here, we report a PM method to improve the mechanical properties of Bi 2 Te 3 -based TE materials through the crushing and hot pressing of Bi 2 Te 3 ingots obtained by ZM. Besides, we demonstrate the TE properties of n-type Bi 2 Te 2.7 Se 0.3 (BTS) to be remarkably improved by Cu doping, which enables optimization of the carrier concentration and enhances phonon scattering at heterointerphases thus increasing the Seebeck coefficient and reducing thermal conductivity. Overall, optimized materials reach dimensionless TE figures of merit (ZT) up to 1.16 at 408 K, i.e. 45% higher than that of state-of-the-art BTS, and an average ZT value of 1.08 in the temperature range of 300–473 K. [ABSTRACT FROM AUTHOR]

This paper presents the results of research on the microstructure, mechanical, and tribological properties of Cu/0.5 wt.% MWCNT (multi-walled carbon nanotube) sintered composite materials produced by powder metallurgy. The purpose of this research was to investigate the impact of carbon nanotube modifications on the uniformity of their dispersion and the effectiveness of their bonding with the matrix. The MWCNTs were modified by chemical oxidation. Additionally, a modification of the ingredient mixing method utilizing ultrasonic frequencies was employed. The tests were carried out using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Vickers hardness tests, static compression tests, and wear tests using the pin-on-disc method. Furthermore, mechanical properties and strain distribution analyses of the micro-specimens were conducted using the Micro-Fatigue System (MFS). The implemented modifications had a positive effect on the dispersion of MWCNTs in the copper matrix and on the mechanical and tribological properties of the sinters. [ABSTRACT FROM AUTHOR]

In recent years, for the structural characteristics and design requirements of the integral rotor and disc shaft of the integrated engine, the welding quality and mechanical properties of superalloy weldments have received increasing attention. In this paper, inertia friction welding (IFW) of FGH96 alloy was carried out using different welding parameters, and the homogeneous connection of FGH96 alloy hollow bars was successfully realized. The microstructure evolution, mechanical properties and fracture failure of the welded joints at room and high temperatures were investigated. The FGH96 alloy IFW joints were divided into the weld nugget zone (WNZ), the thermo-mechanically affected zone (TMAZ), the heat-affected zone (HAZ) and the base metal (BM), and there were significant differences in grain structure and distribution of the γ′ phase in each of the characteristic zones. The microhardness and tensile properties of the IFW joints were investigated, and the results showed an "M"-shaped curve in the microhardness distribution, with the lowest point of hardness observed in the HAZ. The tensile test results indicated that the fracture position moved from the BM to the WNZ with the increase in temperature, the microstructure at the fracture changed significantly and the tensile strength decreased from 1512.0 MPa at room temperature to 1201.3 MPa at 750 °C. The difference in the mechanical properties of the joints was mainly attributed to the changes in the dissolution and precipitation of the γ′ phase. [ABSTRACT FROM AUTHOR]

High-quality Fe-Cr-Ni-W-B spherical powder is crucial for the powder metallurgy preparation of high-strength and tough Fe-Cr-Ni-W-B alloys. In this study, the controlled preparation of high-quality Fe-Cr-Ni-W-B spherical powder was achieved using the vacuum gas atomization method. The effects and mechanisms of atomization gas pressure, the melt nozzle inner diameter, and heat treatment temperature on the microstructure and flowability of Fe-Cr-Ni-W-B spherical powder were systematically investigated. By optimizing process parameters, spherical Fe-Cr-Ni-W-B powder with a sphericity of 95.1% and a flowability of 15.88 s/50 g was obtained, laying the foundation for the powder metallurgy preparation of high-strength and tough Fe-Cr-Ni-W-B alloys. [ABSTRACT FROM AUTHOR]

Dendrites and side reactions of Zn anodes severely restrict the application of aqueous Zn‐based batteries for grid‐scale energy storage. While surface/interface modification strategies have shown some progress in improving Zn anode reversibility, they still fall short in addressing the overall regulation and intrinsic mechanisms from the bulk‐phase perspective. Herein, a bulk‐phase composite Zn/CNTs anodes fabricated by a powder‐metallurgy‐based strategy is introduced. Benefiting from the regulation of grain boundary engineering on local electric conductivity, electric field distributions, and Zn atom absorption energy, the Zn/CNTs anodes effectively suppress dendrite growth and enhance corrosion resistance during Zn stripping/plating cycles. Symmetrical cells equipped with Zn/CNT4 anodes exhibit extended cycling stability with minimal voltage hysteresis (only 22 mV). Furthermore, the full cells incorporating Zn/CNT4 with commercial MnO2 demonstrate superior rate performance and specific capacitance retention after 500 h cycling. This breakthrough opens up new avenues for optimizing metallic anodes at the bulk phase level using powder metallurgy, enabling scalable manufacturing processes, and providing valuable insights for various metal anode systems. [ABSTRACT FROM AUTHOR]

Aqueous Zn‐based batteries have emerged as compelling candidates for grid‐scale energy storage, owing to their intrinsic safety, remarkable theoretical energy density and cost‐effectiveness. Nonetheless, the dendrite formation, side reactions, and corrosion on anode have overshadowed their practical applications. Herein, we present an in situ grown carbon network reinforcing Zn matrix anode prepared by powder metallurgy. This carbon network provides an uninterrupted internal electron transport pathway and optimize the surface electric field distribution, thereby enabling highly reversible Zn deposition. Consequently, symmetrical cells demonstrate impressive stability, running for over 880 h with a low voltage hysteresis (≈32 mV). Furthermore, this Zn matrix composite anode exhibits enhanced performance in both the aqueous Zn‐ion and the Zn‐air batteries. Notably, Zn//MnO2 cells display superior rate capabilities, while Zn‐air batteries deliver high power density and impressive Zn utilization rate (84.9 %). This work provides a new idea of powder metallurgy method for modified Zn anodes, showcasing potential for large‐scale production. [ABSTRACT FROM AUTHOR]

Aqueous Zn‐based batteries have emerged as compelling candidates for grid‐scale energy storage, owing to their intrinsic safety, remarkable theoretical energy density and cost‐effectiveness. Nonetheless, the dendrite formation, side reactions, and corrosion on anode have overshadowed their practical applications. Herein, we present an in situ grown carbon network reinforcing Zn matrix anode prepared by powder metallurgy. This carbon network provides an uninterrupted internal electron transport pathway and optimize the surface electric field distribution, thereby enabling highly reversible Zn deposition. Consequently, symmetrical cells demonstrate impressive stability, running for over 880 h with a low voltage hysteresis (≈32 mV). Furthermore, this Zn matrix composite anode exhibits enhanced performance in both the aqueous Zn‐ion and the Zn‐air batteries. Notably, Zn//MnO2 cells display superior rate capabilities, while Zn‐air batteries deliver high power density and impressive Zn utilization rate (84.9 %). This work provides a new idea of powder metallurgy method for modified Zn anodes, showcasing potential for large‐scale production. [ABSTRACT FROM AUTHOR]

Guillaume stunned the scientific community in 1897 by reporting a very low CTE in Fe36Ni alloy, which also named invar 36. The anomalous CTE feature makes invar 36 an indispensable material in a wide range of critical applications, including high precision optics, laser components, composite molds in aeronautical industry, and various instruments in spacecraft. However, the main drawback of invar 36 is that it is a ductile material, and thus, its machinability is poor. The problem is afore-mentioned applications mostly necessitate invar 36 to be machined into various complex shapes, and thus, mechanical properties of invar 36 should be improved in most cases. Many strategies have been studied to improve the mechanical properties of invar 36, including utilization of different manufacturing methods, introduction of numerous alloying elements, and application of various post-processes. The most common manufacturing methods of invar 36 are casting, powder metallurgy, and additive manufacturing. Casting allows rapid manufacturing and it is relatively cheap, thus, enables mass production of small to large-sized parts. Powder metallurgy is a versatile alternative to casting since it allows preparation of complex shapes from small to large volume that are close to net shape with almost no loss of raw materials. Recently, additive manufacturing is proposed to prepare invar 36 with complex shapes without a severe impurity problem. As one could expect, not only the mechanical properties, but also the puzzling thermal expansion behavior of invar 36 strongly depends on manufacturing methods as well as post-processes. This paper intends to provide a comprehensive and critical review of the research activities on invar 36. Previous studies are discussed in terms of process-structure-property relation, on-going challenges and conflicts are highlighted, and author opinions are provided with an intention of serving as a guide for future studies. [ABSTRACT FROM AUTHOR]

In this study, the effect of different amounts of molybdenum disulfide (MoS2) content on the microstructure and mechanical properties of Cu–10Al–4Ni–4.8Fe powder alloys was investigated. The results showed that the alloy initially consisted of KⅠ, KⅡ, KⅢ, and α phases without MoS2. However, when 2% MoS2 content was added, the lamellar Cu1.84Mo6S8 phase appeared in the alloy, and with increasing MoS2 content, the lamellar Cu1.84Mo6S8 phase and the number of pores increased. A gradual increase in the MoS2 content initially increased the sintered density, hardness, and yield strength of the alloy and then decreased. The sintered density and hardness reached their maximum values at 2% MoS2 content, while the yield strength reached its maximum value at 4% MoS2 content. With increasing MoS2 content, the friction coefficient fluctuated, while the wear loss decreased after first increasing. By applying the study results, the wear resistance of aluminum-bronze powder alloys can be improved to meet its rapidly growing industrial requirements. [ABSTRACT FROM AUTHOR]

Titanium matrix composites reinforced with ceramic particles are considered a promising engineering material due to their combination of high specific strength, low density, and high modulus. In this study, the TA15-based composites reinforced with a volume fraction of 10% to 25% (TiB+TiC) were prepared using powder metallurgy and casting technique. Microstructural characterization and phase constitution were examined using optical microscopy (OM), scanning electron microscopy (SEM), and X-ray diffraction (XRD). In addition, the microhardness, room temperature (RT) and high temperature (HT) tensile properties of the composites were evaluated. Results revealed that the reinforcements are distributed uniformly even in the composites with a high volume of TiB and TiC. However, as the volume fraction exceeds 15%, TiB and TiC particles become coarsening and exhibit rod-like and dendritic-like morphology. Microhardness increases gradually from 321.2 HV for the base alloy to a maximum of 473.3 HV as the reinforcement increases to 25vol.%. Tensile test results indicate that a reinforcement volume fraction above 20% is beneficial for enhancing tensile strength and yield strength at high temperatures, but it has an adverse effect on room temperature elongation. Conversely, if the reinforcement volume fraction is below 20%, it can improve high-temperature elongation when the temperature exceeds 600 °C. [ABSTRACT FROM AUTHOR]

In this work, a new use of mixed Ti-6Al-4V powder, consisting of the retained powder after screening for additive manufacturing and the recycled powder after multiple printing, has been exploited. The powder mixture has been hot-isostatically-pressed (HIPed) at 930 °C/120 MPa for 3 h to reach full density. The hot deformation behavior of the as-HIPed powder compacts were investigated through isothermal compression tests, kinetic analyses, and hot processing maps. Finally, the optimized hot working parameters were validated using upsetting tests. The results show that the as-HIPed Ti-6Al-4V alloy has a fine and homogeneous microstructure. The activation energies were calculated to be 359 kJ/mol in the α + β phase regime and 463 kJ/mol in the β phase regime, respectively. The optimal hot working parameters are a deformation temperature above 950 °C and strain rate higher than 0.1 s−1. The hot workability of as-HIPed powder compacts is better than the as-cast billets. The deformed microstructure can be finer than that of as-HIPed state, and the mechanical performance can be further improved by the optimal thermo-mechanical processing treatment. [ABSTRACT FROM AUTHOR]

In this study, the effect of ball milling on microstructure and hardness of Al7075 - 15 wt% SiC - 1 wt% MWCNT nanocomposite was investigated as a function of milling time up to 20 h. Mechanically alloyed powders were consolidated by cold pressing followed by sintering at 560°C for 1 h in an argon atmosphere. The structural characterization of nanocomposites was conducted by a X-ray diffractometer (XRD), optical microscopy (OM), scanning electron microscopy (SEM), and grain size analyses. The hardness of samples was measured by using Wolpert Wilson-400 micro-hardness testing equipment comprising of a Vickers indenter. The structural defects of pristine and milled MWCNTs were calculated by using defect and carbon intensity ratio (ID/IG) resulted from Raman spectroscopy. The results indicate that after ball milling, the grain size decreases depending on the milling time, the intermetallic Al4C3 phase is formed as a result of the reaction between the matrix and the MWCNT particles, and the MWCNT structure is destroyed. The finest grain size and highest hardness values were obtained as 483 nm and 134 HV, respectively, after 15 h of grinding. [ABSTRACT FROM AUTHOR]

Five high-entropy carbonitride ceramic (HECN) powders consisting of pentavalent cations (Ti,W,Mo,Nb,Ta) (C 0.78 ,N 0.22) are synthesized by the carbothermal reduction-nitridation (CRN) method. Subsequently, a series of 85HECN-7.5Co-7.5Ni(wt.%) cermet is fabricated employing the powder metallurgy method. The phase constitution, microstructure, and composition distribution of the HECN powders are analyzed. The synthesis temperature of the HECN powders is reduced by 100 °C compared to the non-high-entropy (Ti,Me) (C,N) ceramic powder when ΔS mix >1.5R, which demonstrates that the high entropy effect promotes the synthesis of solid solution powder. A uniform element distribution, 600 nm single-phase (Ti 0.6 ,W 0.1 ,Mo 0.1 ,Nb 0.1 ,Ta 0.1) (C 0.78 ,N 0.22) high-entropy ceramic solid solution powder, could be synthesized through the CRN at 1400 °C for 2 h under a 2 kPa N 2 atmosphere. Subsequently, five types of (Ti,W,Mo,Nb,Ta) (C 0.78 ,N 0.22)-Co-Ni high-entropy cermets are prepared via vacuum sintering at 1500 °C for 1 h. Among them, the (Ti 0·6 W 0·1 Nb 0·1 Ta 0·1 Mo 0.1) (C 0.78 ,N 0.22)-Co-Ni cermet exhibited the most outstanding performance with a Vickers hardness of 2053.4 HV, fracture toughness of 12.3 MPa m1/2, and TRS of 1220 MPa, which present an increase of 17.0 %, 16.2 %, and 60.0 %, respectively, compared with the non-high-entropy TiCN–Co–Ni cermet. It was attributed to the addition of high-entropy ceramic powders, which resulted in fine grain strengthening, severe lattice distortion, and long crack deflection paths. This study presents a novel approach for the preparation of high-entropy Ti(C,N)-based cermets. [ABSTRACT FROM AUTHOR]

More focus has recently been placed on enhancing the strength, elastic modulus, coefficient of thermal expansion (CTE), wear and corrosion resistance, and other qualities of aluminum (Al) alloys by varying the quantity of ceramics added for a range of industrial uses. In this regard, Al-4.2-Cu-1.6Mg matrix nanocomposites reinforced with nano-ZrO2 particles have been created using the powder metallurgy approach. The microstructure and particle size distributions of the produced powders were analyzed using a diffraction particle size analyzer, XRD, TEM, and SEM. To achieve good sinterability, the powders were compacted and sintered in argon. The sintered nanocomposites' mechanical, elastic, and physicochemical characteristics were measured. Additionally, the behavior of corrosion, wear, and thermal expansion were examined. The results showed a decrease in the particle sizes of the Al-Cu-Mg alloy by adding ZrO2 nanoparticles up to 45.8 nm for the composite containing 16 wt.% ZrO2. By increasing the sintering temperature to 570 °C, the densification of nanocomposites was enhanced. Also, the coefficient of thermal expansion and wear rate remarkably decreased by about 28 and 37.5% by adding 16 wt.% ZrO2. Moreover, microhardness yield, strength, and Young's modulus were enhanced to 161, 145, and 64%, respectively, after adding 16 wt.% ZrO2. In addition, increasing the exposure time was responsible for decreasing the corrosion rate for the same sample. [ABSTRACT FROM AUTHOR]

A gas atomised Ti-6Al-4V powder, classified as out-of-specification for additive manufacturing (AM), was consolidated via Field-Assisted Sintering Technology (FAST). Fully dense 250 mm diameter discs with lamellar or bimodal microstructures were produced by FAST processing either above or below the β-transus temperature. Static and dynamic mechanical properties were assessed by testing full-size specimens in the 'as-FAST' condition. Material from both processing conditions exceeded the ASTM Ti-6Al-4V powder metallurgy requirements for yield/tensile strength and elongation. Furthermore, material from the edge of the disc processed below the β-transus temperature meets ASTM requirements for wrought Ti-6Al-4V. Fatigue performance also compared favourably with conventionally processed Ti-6Al-4V. This work establishes that surplus AM powders can be successfully recycled via the one-step FAST process and provides confidence that this ASTM-grade material can be used in a range of applications under both static and dynamic loading, which will improve the sustainability credentials of the AM sector. [ABSTRACT FROM AUTHOR]

Electromagnetic axial powder compaction (EMAPC) uses strong magnetic fields to compact powder metallurgy components at high speeds. Lorentz forces accelerate the punch to compact powder in EMAPC. Thus, high magnetic fields cause powder deformations in microseconds. Therefore, measuring the compact height, magnetic field distribution, and compaction velocity was difficult. No literature has reported EMAPC finite element (FE) modeling. Thus, an LS-DYNA multi-physics solver-based FE 3D model has been developed to study SS316s EMAPC. A cylindrical SS316 sample was simulated for EMAPC at various discharge energies. The powder-compressed sample's final deformation was predicted through simulation. To characterize compacted samples, sintered samples were studied for density, porosity, and microhardness. Compressed samples were microscopically examined using optical microscopy. Increased discharge energy lowers height, increases density, and microhardness. FE analysis can be used to optimize EMAPC process parameters for powder compact density and porosity. [ABSTRACT FROM AUTHOR]