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In this work, an equiatomic Ti-V-Al-Nb-Hf high-entropy alloy (HEA) was designed by thermodynamic simulation and prepared experimentally via a powder metallurgy approach. A nanoindentation and nano scratch technique was used to study the mechanical and friction behavior of the HEA. The results revealed that a nano hardness of 7.39 ± 0.4 GPa and an elastic modulus of 140.75 ± 6.3 GPa was achieved. The coefficient of friction (COF) and creep behavior of the alloy were studied by scratch tests in ramping mode under constant-loading conditions. The COF quickly increased as the normal load increased at the beginning stage of creep performance. Additionally, three-dimensional modeling was performed to obtain a graphical representation, which can be used to explore the morphology and geometry of the scratched track. From the experimental findings, the creep behavior of the alloy is classified into two separate regimes: transient and steady-state regions. The present study demonstrates the scratch and creep behavior of the HEA in the context of the scratch mechanisms.

This study investigates single and multilayer TiAlN/CrN nanocomposite thin films developed using an RF magnetron sputtering system. The TiAlN and CrN layers showed a high degree of orientation, with the (200) peak being the strongest peak in both layers, and a multilayer structure was clearly observed. The surface roughness analysis using atomic force microscopy (AFM) and cross-sectional transmission electron microscopy (TEM) revealed that the TiAlN/CrN coatings had a smoother surface than the single-layer coatings and minimal intermixing between the two layers. Depth-sensing indentation measurements were used to measure the hardness and Young’s modulus of the coatings, demonstrating that TiAlN/CrN coating had the highest hardness (~16.38 GPa) and elastic modulus (~3.82 GPa) among all the coatings studied. This indicates that the TiAlN/CrN multilayer coating possesses superior mechanical properties due to its interface strength. Our findings suggest that these multilayer coatings have potential applications in tribological and decorative coatings.

A machine learning technique leveraging artificial intelligence (AI) has emerged as a promising tool for expediting the exploration and design of novel high entropy alloys (HEAs) while predicting their mechanical properties at both room and elevated temperatures. In this paper, we predict the flow stress of hot-compressed CoCrFeNiV HEAs using conventional (qualitative and quantitative models) and advanced machine learning approaches across various temperature and strain rate conditions. Conventional modeling methods, including the modified Johnson-Cook (JC), modified Zerilli–Armstrong (ZA), and Arrhenius-type constitutive equations, are employed. Simultaneously, machine learning models are utilized to forecast flow stress under different hot working conditions. The performance of both conventional and machine learning models is evaluated using metrics such as coefficient of determination (R2), mean abosolute error (MAE), and root mean squared error (RMSE). The analysis reveals that the gradient boosting machine learning model shows superior prediction accuracy (with value R2 = 0.994, MAE = 7.77%, and RMSE = 9.7%) compared to conventional models and other machine learning approaches.

We investigated self-lubricating Al–Mg–Si hybrid metal matrix composites (HMMCs) embedded with MoS2–B4C particulates, for use in automotive engine components. Composites with different B4C content (x = 3.5, 7.0, 10.5, 14.0, and 17 wt%) were prepared, with the MoS2 content of 3.0 wt%. The metal matrix composites were processed using the powder metallurgy route comprising milling for 2 h and cold pressing and consolidation at a sintering temperature of 560 °C. Their dry sliding wear behavior was examined at applied loads (20–50 N) and sliding distances (1–3 km), and the wear variables were optimized using the Taguchi model (L9). Microstructural analysis was performed using a scanning electron microscope equipped with an energy dispersive spectrometer. A homogeneous particle distribution was observed in the HMMCs, without any appreciable instance of agglomerates. The wear resistance and friction coefficient (COF) improved when MoS2 was incorporated into the HMMCs, compared with a matrix alloy under the same operating conditions. In particular, the COF fluctuated up to a sliding distance of 250 m and was constant for larger values. The wear rate depends on not only the maximum hardness but also the appreciation of self-lubricant MoS2. The Taguchi findings showed that the fraction of hybrid reinforcement had the strongest effect on the wear resistance, and it was followed by the applied load, sliding distance, and track diameter. Apart from providing self-lubrication, the MoS2 particles reduced the wear rate.

Self-lubricating aluminum matrix composites (AMCs) can be used to reduce the wear and coefficient of friction (COF) in automotive engine components in which the use of liquid lubricants is not desirable. High temperatures accelerate the oxidation and thermal degradation of a liquid lubricant. In this study, we used powder metallurgy (PM) technique to prepare self-lubricant (MoS2)-based Al–Mg–Si AMCs, designated as Al–Mg–Si–xMoS2 (x in wt.%; x = 1.5, 2.0, 30, 3.5, and 4.0). The dry sliding wear properties were assessed using a pin-on-disk tribometer at various applied loads (20–50 N) and sliding distances (1000–3000 m), based on the Taguchi model (L9). Furthermore, electrochemical corrosion tests such as open circuit potential (OCP) and potentiodynamic polarization (PDP) were performed in a 3.5 wt% NaCl medium. The morphology of the Al–Mg–Si–xMoS2 composites was observed through scanning electron microscopy and energy dispersive spectroscopy to clarify the particle distribution and chemical composition. The results indicated that the addition of MoS2 to Al–Mg–Si decreased the wear and COF and increased the corrosion resistance, compared with those of the pristine Al–Mg–Si matrix alloy under same operating conditions. As the sliding distance increased to 250 m, the COF fluctuated, but it stabilized as the distance approached 3000 m. The effects of the load and reinforcement concentration were more significant than those of the sliding distance and track diameter, as predicted by the Taguchi model and analysis of variance methods.

In this study, the impact of heat treatments on AlFeCuCrMgx (x = 0, 0.5, 1, and 1.7) alloys prepared by mechanical alloying and spark plasma sintering were examined. The behavior of these high-entropy alloys (HEAs) was thoroughly studied after they had been heated to 470, 600, and 820 °C in a natural atmosphere. X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to study the phase evolution of the heat-treated alloys. The XRD data of the AlFeCuCrMgx (x = 0 and 0.5) alloys heated at 470, 600, and 820 °C present the dispersion of FCC Cu particles at the grain boundaries of parental phases. By contrast, the AlFeCuCrMgx (x = 1 and 1.7) alloys do not exhibit this characteristic. The microstructures of these alloys have been correlated with these results. Their sub-micron structures indicate that the precipitates are unaffected up to 820 °C. The impact of elevated temperatures on the AlFeCuCrMgx alloys was thoroughly examined based on conventional theory.

Developing materials with superior strength and wear resistance has always drawn challenging research for advanced engineering applications. Herein, considerable efforts have been devoted to enhancing the strength and wear resistance of face-centered cubic (FCC)-structured CoCrFeMnNi high entropy alloy (HEA) by incorporating HfO2 nanoparticles (NPs) through a powder metallurgy approach. The phase composition, microstructure, mechanical, and tribological properties of HEA composites were investigated. The XRD results reveal that the composite powders consisted of the FCC solid solution along with minor HfO2 phases. In addition, sintered HEAs showed the major FCC phase along with minor Cr-rich and HfO2 phases. Microscopic results confirmed the uniform distribution of HfO2 NPs throughout the matrix during the milling process. With increasing HfO2 contents, the hardness of the HEAs increased from 270 ± 10 to 520 ± 10 HV, while the compressive yield strength increased from 370 to 1500 MPa, due to dispersion and grain boundary strengthening effects. Furthermore, composite HEAs showed a decrease in coefficient of friction and wear rates with increasing HfO2 content due to increased surface hardness and transition in wear mechanism from severe wear to mild abrasive wear. The present study demonstrates the feasibility of producing high-performance oxide dispersion-strengthened HEAs for advanced structural applications.

The isothermal oxidation behavior of multi-component high entropy alloys (HEAs), namely AlCuCrFeMn, AlCuCrFeMnW0.05, AlCuCrFeMnW0.1, and AlCuCrFeMnW0.5, was investigated and the behavior of the oxide layer was analyzed. All four HEAs were synthesized via mechanical alloying (MA) and consolidated by spark plasma sintering (SPS). The samples were oxidized in the air atmosphere at a temperature of 500 °C for 50 h. Based on the thermogravimetric result, the oxidation rate of the materials decreased with the increase of W content, and the values of parabolic constants were on a level similar to those observed in Ni–Al superalloys. However, higher content of W improves the continuity and internal position of the WO3 scale, which leads to increased oxidation resistance. Throughout the oxidation process, the composition of the phases of all materials changed significantly. The triple-thick oxide layer formed of Al2O3, Cr2O3, and WO3, developed in HEAs, has been carefully studied using the XPS technique.

This work mainly focuses on the sintering behavior of the Cu-Sn alloy with the addition of Ag up to 4 wt% after pulsed electric current sintering (PECS) process for ultra-fast sintering. The microstructural evolution was characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and density measurements. The mechanical properties were evaluated via measurements of transverse rupture strength (TRS) and Rockwell hardness. The mechanism during the sintering process has been discussed thoroughly, and the effect on porosity with the addition of the Ag is also correlated. The results showed that the growth of porosity progressed with the amount of Ag up to 2 wt%, and further addition of Ag leads reduction in porosity. The effect on mechanical properties were improved slowly as the amount of Ag increased.

Tungsten diselenide (WSe2) is one of the promising transition metal dichalcogenides (TMDs) for nanoelectronics and optoelectronics. To enhance and tune the electronic performance of TMDs, chemical functionalization via covalent and van der Waals approaches has been suggested. In the present report, the electric and structural transition of WSe2 oxidized by exposure to O3 is investigated using scanning tunneling microscopy. It is demonstrated that the exposure of WSe2/high-ordered pyrolytic graphite sample to O3 induces the formation of molecular adsorbates on the surface, which enables to increase in the density of states near the valence band edge, resulting from electric structural modification of domain boundaries via exposure of atomic O. According to the work function extracted by Kelvin probe force microscopy, monolayer WSe2 with the O3 exposure results in a gradual increase in work function as the exposure to O3. Therefore, the present report demonstrates the potential pathway for the chemical functionalization of TMDs to enhance the electric performance of TMDs devices.

As the amount of high-capacity secondary battery waste gradually increased, waste secondary batteries for industry (high-speed train & HEV) were recycled and materialization studies were carried out. The precipitation experiment was carried out with various conditions in the synthesis of LiNi0.6Co0.2Mn0.2O2 material using a Taylor reactor. The raw material used in this study was a leaching solution generated from waste nickel-based batteries. The nickel-cobalt-manganese (NCM) precursor was prepared by the Taylor reaction process. Material analysis indicated that spherical powder was formed, and the particle size of the precursor was decreased as the reaction speed was increased during the preparation of the NCM. The spherical NCM powder having a particle size of 10 µm was synthesized using reaction conditions, stirring speed of 1000 rpm for 24 hours. The NCM precursor prepared by the Taylor reaction was synthesized as a cathode material for the LIB, and then a coin-cell was manufactured to perform the capacity evaluation.

The objective of the present research is to develop new admixed lubricants which can be used for high-density sintered iron when processed using warm die and warm compaction. Depending on various lubricants, the effect of compaction temperature on the ejection behavior and sintered properties was studied. Lubricants were prepared by mixing of Zn-stearate and ethylene bis stearamide (EBS) in various compositions. The iron powders blended with lubricants were compacted under the pressure of 700 MPa at various temperatures. The green compacts were sintered at 1120°C for 30 min. Microstructure, density, hardness, and transverse rupture strength of sintered materials with different lubricants were investigated in detail.

In this work, we have designed a new high entropy alloy containing lightweight elements, e.g., Al, Fe, Mn, Ti, Cu, Si by high energy ball milling and spark plasma sintering. The composition of Si was kept at 0.75 at% in this study. The results showed that the produced AlCuFeMnTiSi0.75 high entropy alloy was BCC structured. The evolution of BCC1 and BCC2 phases was observed with increasing the milling time up to 60 h. The spark plasma sintering treatment of milled compacts from 650-950°C showed the phase separation of BCC into BCC1 and BCC2. The density and strength of these developed high entropy alloys (95-98%, and 1000 HV) improved with milling time and were maximum at 850°C sintering temperature. The current work demonstrated desirable possibilities of Al-Si based high entropy alloys for substitution of traditional cast components at intermediate temperature applications.

Due to the limitations of utilizing pure metals, several elements were combined to make an alloy in order to provide and improve certain features as needed for the application. The concept of alloy making has diversified over a thousand years. In addition, A new concept of alloy design has been discovered early decades and named high entropy alloy (HEA). Multiple principal elements are being adopted with a high concentration to develop new material. The multi-dimension composition space has several unrevealed properties that the researchers are exposing. However, an ample number of properties have been uncovered. Despite this, alloys based on intermetallic compounds have developed as high-temperature materials with the primary goal of replacing nickel-based superalloys due to their low melting temperatures. For applications in sensitive environments, there is still a lot of interest, thus these alloys are continuously being developed. Mechanical strength, microstructural stability, and corrosion/oxidation resistance are all requirements for alloys used in high-temperature applications. High entropy alloys may be the primary materials used in aviation turbine engine hot section components and high-temperature environments.Nevertheless, there must be many other concealed properties to date, and it is likely to be discovered soon, seeing the ample research going on it. In this urge, this review explores the up-to-the-minute milestones in the high-temperature application achieved by the HEAs. The conversant assessment also includes different processing routes of HEAs, properties at high temperatures, and advanced HEAs that could be exploited for high-temperature applications. In a nutshell, this artifact emphasizes the potential application of HEAs that could be advanced high-temperature materials in the future. Thus, the review outlines HEAs and covers various advantageous information for working on materials exposed to high-temperature applications.

Abstract In this work, we studied the brazing characteristics of Al2O3 and 3D printed Ti–6Al–4V alloys using a novel equiatomic AlZnCuFeSi high entropy alloy filler (HEAF). The HEAF was prepared by mechanical alloying of the constituent powder and spark plasma sintering (SPS) approach. The filler microstructure, wettability and melting point were investigated. The mechanical and joint strength properties were also evaluated. The results showed that the developed AlZnCuFeSi HEAF consists of a dual phase (Cu–Zn, face-centered cubic (FCC)) and Al–Fe–Si rich (base centered cubic, BCC) phases. The phase structure of the (Cu–Al + Ti–Fe–Si)/solid solution promises a robust joint between Al2O3 and Ti–6Al–4V. In addition, the joint interfacial reaction was found to be modulated by the brazing temperature and time because of the altered activity of Ti and Zn. The optimum shear strength reached 84 MPa when the joint was brazed at 1050 °C for 60 s. The results can be promising for the integration of completely different materials using the entropy driven fillers developed in this study.

In the past few years, overhead copper transmission lines have been replaced by lightweight aluminum transmission lines to minimize the cost and prevent the sagging of heavier copper transmission lines. High strength aluminum alloys are used as the core of the overhead transmission lines because of the low strength of the conductor line. However, alloying copper with aluminum causes a reduction in electrical conductivity due to the solid solution of each component. Therefore, in this study, the authors attempt to study the effect of various Al/Cu ratios (9:1, 7:3, 5:5) to obtain a high strength Al-Cu alloy without a significant loss in its conductivity through powder metallurgy. Low-temperature extrusion of Al/Cu powder was done at 350ºC to minimize the alloying reactions. The as-extruded microstructure was analyzed and various phases (Cu9Al4, CuAl2) were determined. The tensile strength and electrical conductivity of different mixing ratios of Al and Cu powders were studied. The results suggest that the tensile strength of samples is improved considerably while the conductivity falls slightly but lies within the limits of applications.

Research on harvesting alternative energy sources is of interest to meet human demands for energy while reducing environmental pollution caused by the extensive use of fossil fuels. Thermoelectric materials are a promising technology for converting heat into electricity. Among thermoelectric materials, the binary bismuth telluride system (Bi-Te) is widely used. To produce high-quality Bi-Te systems with low materials consumption, spark plasma sintering (SPS) is commonly applied. Because SPS is a fast low-temperature process, controlling the ratio and crystallization of Bi-Te is critical for effective energy conversion. Here, we investigated the quality of Bi-Te systems formed by SPS compaction of raw powders with an in-depth examination of the oxidation effects on their thermoelectric performance. With increasing measurement temperature (300→420 K), the mechanically mixed sample and a commercial Bi2Te3 alloy (sintered at 533 K) showed differences in Seebeck coefficients (0.245→0.267 and 0.223→0.246 mVK−1, respectively). The alloy sample showed a decreased figure of merit (0.863→0.331) while that of the mechanically mixed sample (0.543→1.671) increased with temperature. This was related to the degree of oxygen impurity in each Bi-Te process based on XPS analysis. This study proposes that the integration of oxygen species to Bi-Te can be considered to maximize the thermoelectric efficiency at the specified temperature.

Al-CuO is a thermite material exhibiting the exothermic reaction only when aluminum melts. For wide spread of its application, the reaction temperature needs to be reduced in addition to the enhancement of total reaction energy. In the present study, a thermite nanocomposite with a large contact area between Al and CuO was fabricated in order to lower the exothermic reaction temperature and to improve the reactivity. A cryomilling process was performed to achieve the nanostructure, and the effect of composition on the microstructure and its reactivity was studied in detail. The microstructure was characterized using SEM and XRD, and the thermal property was analyzed using DSC. The results show that as the molar ratio between Al and CuO varies, the fraction of uniform nanocomposite structure was changed affecting the exothermic reaction characteristics.

Pre-alloyed Astaloy CrLTM (Fe-1.5 wt% Cr-0.2 wt% Mo), a commercial Fe-based alloy powder for high strength powder metallurgy products, was sintered and hot forged with additions of 0.5 wt% C and 0~2 wt% Cu. To investigate the influence of various Cu contents, the microstructural evolution was characterized using density measurements, scanning electron microscope (SEM) and electron backscatter diffraction (EBSD). Transverse rupture strength (TRS) was measured for each composition and processing stage. The correlation between Cu additions and properties of sinter-forged Fe-Cr-Mo-C alloy was discussed in detail.

The objective of the present research is to develop the novel multi-compaction technology to produce hybrid structure in powder metallurgy (P/M) components using dissimilar Fe-based alloys. Two distinct powder alloys with different compositions were are used in this study: Fe-Cr-Mo-C pre-alloyed powder for high strength and Fe-Cu-C mixed powder for enhanced machinability and lower material cost. Initially, Fe-Cu-C was pre-compacted using a bar-shaped die with lower compaction pressure. The green compact of Fe-Cu-C alloy was inserted into a die residing a half of the die, and another half of the die was filled with the Fe-Cr-Mo-C powder. Then they subsequently underwent re-compaction with higher pressure. The final compact was sintered at 1120°C for 60 min. In order to determine the mechanical behavior, transverse rupture strength (TRS) and Vickers hardness of sintered materials were measured and correlated with density variations. The microstructure was characterized using optical microscope and scanning electron microscope to investigate the interfacial characteristics between dissimilar P/M alloys.

In the field of electronics packaging, Pb-bearing solder alloys are mostly used as robust interconnecting materials [...]

Among laser additive manufacturing, selective laser melting (SLM) is one of the most popular methods to produce 3D printing products. The SLM process creates a product by selectively dissolving a layer of powder. However, due to the layerwise printing of metal powders, the initial microstructure is fully acicular α′-martensitic, and mechanical properties of the resultant product are often compromised. In this study, Ti-6Al-4V alloy was prepared using SLM method. The effect of heat treatment was carried out on as-built SLM Ti-6Al-4V alloy from 650–1000 °C to study respective changes in the morphology of α/α′-martensite and mechanical properties. The phase transition temperature was also analyzed through differential thermal analysis (DTA), and the microstructural studies were undertaken by optical microscopy (OM) and scanning electron microscopy (SEM). The mechanical properties were assessed by microhardness and compressive tests before and after heat treatment. The results showed that heat treated samples resulted in a reduction in interior defects and pores and turned the morphology of the α′-martensite into a lamellar (α + β) structure. The strength was significantly reduced after heat treatment, but the elongation was improved due to the reduction in columnar α′-martensite phase. An optimum set of strength and elongation was found at 900 °C.

The development of lightweight HEAs with high strength and low cost is an urgent requirement. In this study, equimolar AlCuSiFeX (X = Cr, Mn, Zn, Sn) lightweight HEAs were fabricated by advanced powder metallurgy. The mechanical alloying was performed for 45 h, and the powder compacts were densified at 650 °C. The final results revealed that AlCuSiFeSn lightweight HEA was composed of a single face-centered cubic (FCC) and Cu81Sn22, whereas AlCuSiFeZn showed a dual FCC and body-centered cubic (BCC) structures. Similarly, AlCuSiFeMn alloy contained a BCC + FCC phase with a µ-phase, whereas a σ-phase was present in AlCuSiFeCr in addition to FCC + BCC phases. We also calculated various thermodynamic parameters to predict the solid-solution phase stability of each of the above lightweight HEAs. It was found that lightweight HEAs with additive elements Sn and Zn tend to predominant FCC phases, whereas those with Cr and Mn result in major BCC with hard µ and σ phases, which further improve their mechanical strength. A maximum fracture strain of 23% was obtained for AlCuSiFeSn followed by 19% for AlCuSiFeZn HEA. The compressive fracture mechanisms of these lightweight HEAs are also discussed and reported here.

Brazing fillers for joining applications are essential for manufacturing and designing advanced materials. Several types of brazing fillers have been developed in recent decades to join similar or different engineering materials. Important parts of automotive and aircraft components, including steel, are often joined by brazing. In addition, ceramic components in microwave devices and circuits have been joined with a high level of integration in microelectronic devices. Similarly, in the medical field, metallic implants have been brazed to ceramic dental crowns. These advances have made human life more convenient. However, in brazing, there are certain issues with intermetallic compound (IMC) formation and residual stresses in joints at high temperatures. Nanoparticle-reinforced fillers have been proposed to control IMCs, but there are other dispersion and particle segregation issues at the joints. In this study, various types of brazing fillers, joint fabrication processes, and brazing technologies developed in recent decades are reviewed. Furthermore, new developments in brazing materials and their specific applications are presented. Finally, the emerging areas in brazing, including the recent entropy-modified brazing fillers for various structural and technological fields, are discussed.

In this work, we have attempted to develop the Ag-Cu-Ti filler for bonding ZrO2 to Ti-6Al-4V. The CeO2 nanoparticles were reinforced in the eutectic Ag-Cu-Ti filler via mechanical mixing and melting route. Furthermore, the brazeability, microstructure, and mechanical behavior, as well as brazing performance of the ZrO2/Ti-6Al-4V joints, were assessed. The wettability of the Ag-Cu-Ti matrix was increased from 89 to 98% on Ti-6Al-4V and from 83 to 89% on the ZrO2 substrate after the addition of 0.05% CeO2. Also, there was a depression in the melting point of the composite fillers up to 3°C. The microstructure consists of Cu- and Ag-rich phases and Cu-Ti intermetallic compounds (IMCs). The joint shear strength was improved with the addition of CeO2 up to 0.05 wt.% in the matrix. It was inferred that, for an excellent brazing performance of the ZrO2/Ti-6Al-4V joint, the optimum amount of CeO2 should be 0.05 wt.% in the Ag-Cu-Ti matrix.

This study investigated the effect of sandblasting particle size on the surface topography and compressive stresses of conventional zirconia (3 mol% yttria-stabilized tetragonal zirconia polycrystal; 3Y-TZP) and two highly translucent zirconia (4 or 5 mol% partially stabilized zirconia; 4Y-PSZ or 5Y-PSZ). Plate-shaped zirconia specimens (14.0 × 14.0 × 1.0 mm3, n = 60 for each grade) were sandblasted using different Al2O3 sizes (25, 50, 90, 110, and 125 μm) under 0.2 MPa for 10 s/cm2 at a 10 mm distance and a 90° angle. The surface topography was characterized using a 3-D confocal laser microscopy and inspected with a scanning electron microscope. To assess residual stresses, the tetragonal peak shift at 147 cm−1 was traced using micro-Raman spectroscopy. Al2O3 sandblasting altered surface topographies (p < 0.05), although highly translucent zirconia showed more pronounced changes compared to conventional zirconia. 5Y-PSZ abraded with 110 μm sand showed the highest Sa value (0.76 ± 0.12 μm). Larger particle induced more compressive stresses for 3Y-TZP (p < 0.05), while only 25 μm sand induced residual stresses for 5Y-PSZ. Al2O3 sandblasting with 110 μm sand for 3Y-TZP, 90 μm sand for 4Y-PSZ, and 25 μm sand for 5Y-PSZ were considered as the recommended blasting conditions.

In this work, we have investigated the role of high-energy ball milling (HEBM) on the evolution of microstructure, thermal, and wetting properties of an Sn-0.7Cu alloy. We ball-milled the constituent Sn and Cu powders in eutectic composition for 45 h. The microstructural studies were carried out using optical and scanning electron microscopy. The melting behavior of the powder was examined using differential scanning calorimetry (DSC). We observed a considerable depression in the melting point of the Sn-0.7Cu alloy (≈7 °C) as compared to standard cast Sn-0.7Cu alloys. The resultant crystallite size and lattice strain of the ball-milled Sn-0.7Cu alloy were 76 nm and 1.87%, respectively. The solderability of the Sn-0.7Cu alloy was also improved with the milling time, due to the basic processes occurring during the HEBM.

Severe plastic deformation is an attractive processing method for refining microstructures of metallic materials to have ultrafine grain sizes within the submicrometer or even the nanometer levels. Especially, it becomes generally known that processing of metals through the application of high-pressure torsion (HPT) provides the potential for achieving exceptional grain refinement in bulk disk metals. In the present study, a ZK60A magnesium alloy was processed by HPT at room temperature for a series of numbers of revolutions under a constant compressive pressure of 6.0 GPa. The change in texture was examined by X-ray diffraction (XRD) analysis and the evolution of hardness was evaluated using Vickers microhardness measurements to provide a comprehensive understanding of microstructural evolution. The XRD analysis showed the texture changed to weak and random in the early stage of HPT. The hardness results demonstrated that the hardness evolution with increasing equivalent strain follows the strain hardening model without microstructural recovery and the degree of hardenability was calculated as ∼0.07 which implies a high degree of strain hardening toward hardness homogeneity.

The processing of metals through the application of high-pressure torsion (HPT) provides the potential for achieving exceptional grain refinement in bulk metals. Numerous reports are now available demonstrating the application of HPT to a range of pure metals and simple alloys. In practice, excellent grain refinement is achieved using this processing technique with the average grain size often reduced to the true nano-scale range. Contrary to the significant grain refinement achieved in metals during HPT, the models of the hardness evolution are very different depending upon the material properties. For a better understanding of the material characteristics after conventional HPT processing, this report demonstrates the hardness evolutions in simple metals including high-purity Al, commercial purity aluminum Al-1050, ZK60A magnesium alloy and Zn-22% Al eutectoid alloy after processing by HPT. Separate models of hardness evolution are described with increasing equivalent strain by HPT. Moreover, a new approach for the use of HPT is demonstrated by synthesizing an Al–Mg metal system by processing two separate commercial metals of Al-1050 and ZK60A through conventional HPT processing at room temperature.

Bulk nanostructured materials (BNMs) are defined as polycrystalline bulk solids with nanocrystalline (NC) or ultrafine-grained (UFG) microstructures. [...]

In this study, uniform and ordered nanostructured arrays of pure tin (Sn) were produced by the chemical pulse plating method in potentiostatic mode. Bottom metalized anodic aluminium oxide templates were used as the substrates for holding nanostructures during deposition. The plating bath consists of stannous sulfate (SnSO4), sulfuric acid (H2SO4), polyethylene glycol (PEG), and glutaraldehyde as a surfactant. The effect of potentiostatic potential ranging from −0.5 to −3.2 V vs. Ag/AgCl electrode was studied on the growth morphology of nanostructures that were formed. The characterization studies were accomplished by X-ray diffraction (XRD), field emission electron microscopy, and energy dispersive spectroscopy. It was found that several nanostructures were of different shapes and size when the potential was varied. Nanorods were prominent at the deposition potentials of −0.5 and −1.1 V, while a combination of nanostructures (nanorods, nanoplates, and nanoparticles) was predominant at −3.2 V. XRD results show that the nanostructures that were obtained consisted of tetragonal (Sn) structure with a crystallite size of about 20 nm. This process is economically viable and it can be scaled to produce various nanostructures through a careful control of deposition parameters.

The solvothermal decomposition of iron complexes using the heat-up process enables monodisperse Fe3O4 nanoparticle synthesis. Here, we demonstrate that the high reduction potential capability of alkaline metal reagents in the reductive environment allows for pure magnetite phase formation at 200 °C, which is lower than that of typical synthetic method and offers highly crystalline superparamagnetic and ferrimagnetic nanostructures with the ability to control uniformity including spherical and cubic morphology with narrow size distributions. Our method involved reduction of the acetylacetonate and acetate anions to aldehyde and alcohol as an oxygen resource for iron oxide nucleation in an inert condition. For confirming the developed pure surface phase of alkaline metal reagent-assisted magnetite nanoparticle, the magnetic field-dependent shifting of blocking temperature was investigated. The degree of the exchange interaction between core spins and disordered surface spins is attributed to the ratio of core spins and disordered surface spins. The decrease in disordered surface spins deviation due to an enhanced pure phase of magnetite nanoparticles exhibited the negligible shift of the blocking temperature under differently applied external field, and it demonstrated that alkaline metal reagent-induced reductive conditions enable less formation of both disordered surface spins and biphasic nanostructures.

The Al-Ni system is known as a high energy density materials (HEDM) because of its highly exothermic nature during intermetallic compound (IMC) formation. In this study, elemental Al and Ni powder were milled to explore the effect of cryomilling atmosphere on the microstructure and exothermic behavior. Scanning electron microscope (SEM) observations show continuous structural refinement up to 8 h of cryomilling. No IMC phase was detected in the X-ray diffraction (XRD) spectrum. Differential thermal analyzer (DTA) results show two exothermic peaks for 8 h cryomilled powder as compared to that of powder milled for 1 h. The ignition temperature of prepared powder mixture also decreased due to gradual structural refinement. The activation energy was also calculated and correlated with the DTA and SEM results. The cryomilled Al-Ni powder is composed of fine Al-Ni metastable junctions which improve the reactivity at a lower exothermic reaction temperature.

An anti-friction Babbitt alloy-coated bearing made by a casting process is a journal bearing, which is used in an ore cone crusher eccentric. The main purpose of the Babbitt coated eccentric is to provide a low friction to support and guide a rotating shaft. Despite the fact that the Babbitt-coated eccentric offers a low friction coefficient and can be operated without a continuous supply of lubricant, it suffers from mining environments and short service life. In this study, an ultrasonic nanocrystalline surface modification (UNSM) technique was used to further reduce the friction coefficient, to increase the wear resistance, and to extend the service life of the Sn-based Babbitt metal. The friction and wear behavior of the Sn-based Babbitt metal was investigated using a block-on-ring tester under both dry and oil-lubricated conditions. The results of the experiments revealed that the friction and wear behavior of Sn-based Babbitt metal could be improved by the application of the UNSM technique. The friction and wear mechanisms of the specimens were explained and discussed in terms of changes in surface properties—microstructure, surface hardness, surface roughness, etc.

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This study investigates single and multilayer TiAlN/CrN nanocomposite thin films developed using an RF magnetron sputtering system. The TiAlN and CrN layers showed a high degree of orientation, with the (200) peak being the strongest peak in both layers, and a multilayer structure was clearly observed. The surface roughness analysis using atomic force microscopy (AFM) and cross-sectional transmission electron microscopy (TEM) revealed that the TiAlN/CrN coatings had a smoother surface than the single-layer coatings and minimal intermixing between the two layers. Depth-sensing indentation measurements were used to measure the hardness and Young's modulus of the coatings, demonstrating that TiAlN/CrN coating had the highest hardness (~16.38 GPa) and elastic modulus (~3.82 GPa) among all the coatings studied. This indicates that the TiAlN/CrN multilayer coating possesses superior mechanical properties due to its interface strength. Our findings suggest that these multilayer coatings have potential applications in tribological and decorative coatings. [ABSTRACT FROM AUTHOR]