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This work investigates the microstructure characterization and mechanical properties of Al alloy fabricated by additive friction stir deposition (AFSD). Microstructure characterizations of the Al alloy 5B70 base material (BM) and build were compared using optical microscope (OM) and electron back scattered diffraction (EBSD). The hardness distribution in the direction perpendicular to the cross-section of the deposited area was systematically evaluated. Tensile tests were performed on the BM and the build using digital image correlation (DIC), and the real-time stress distribution states of the specimens were analyzed. After the tensile tests, the fracture micromorphology was characterized using scanning electron microscope (SEM). The results indicated that a high degree of recrystallization occurred in the deposition zone, where fine, equiaxed, and differently oriented grains are formed. It was found that the strength of the deposition layer was lower compared to that of the BM, but its toughness was significantly improved. Also, obvious anisotropy of mechanical properties was identified in the deposition layer. [ABSTRACT FROM AUTHOR]

The paper aims to investigate the influence of silver addition on the microstructure of CuNi2Si1 alloys. The investigated copper alloy was cast and then supersaturated, plastically deformed on the Gleeble 3800 simulator and finally aged. Structural changes were examined using optical microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Orientation mapping was completed with FEI Quanta 3D field emission gun scanning electron microscope (SEM) equipped with TSL electron backscattered diffraction (EBSD) system. The effect of structural and microstructural changes on hardness and conductivity was also investigated. Based on the mechanical tests it was found that the mechanical properties and conductivity are improved due to heat and plastic treatment. It was also found that the precipitation hardening raises the hardness to the level of 40% whilst an increase in conductivity by 20% is observed. [ABSTRACT FROM AUTHOR]

The oxide film on the scrap surface is one of the primary sources of oxide inclusions in the aluminum melt. Understanding the evolution of the oxide films in the aluminum melt is an important step for developing efficient recycling technologies and controlling the quality of the product. In the present study, we studied the evolution behavior of the oxide film in the aluminum melt. The oxide films were introduced via aluminum alloy scraps into the melt, and the micro-morphology and composition of the oxide film were analyzed by scanning electron microscope and energy spectrum. Results show that the oxide film on the surface of 1235 alloy foil, A356 alloy turning, and 5083 alloy scalping were broken into small flake oxide film and then transformed into minor granular oxide when the scraps were charged into commercial purity aluminum melt. However, in aluminum alloy melt containing magnesium, the oxide film remained an intact sheet shape up to a certain melt dwelling time. [ABSTRACT FROM AUTHOR]

The hot deformation process significantly affects the performance of the manufactured Zr alloy components in nuclear reactors. The hot deformation behavior of the Zr-1wt.% Nb alloy with an initial β-quenched microstructure was evaluated using hot compression test at the temperature range of 600-950 °C and the strain rate range of 0.001-0.8 s−1. The constitutive equation was determined using kinetic analysis. The strong effect of Nb on decreasing self-diffusion in Zr was the reason for the obtained large activation energy of 390 kJ/mol in the Zr-1Nb alloy. Based on the dynamic material model, the processing map was constructed at the strain of 0.8 to show the stable and unstable hot deformation regions. The microstructural features of the hot deformed samples were observed using optical and scanning electron microscopes. The results indicated that the hot deformed microstructures were fully recrystallized so that the grain size of the as-received microstructure of the Zr-1Nb alloy was reduced from 1 mm to less than 4 μm after hot deformation at 800 °C. The optimum region in the hot deformation of the Zr-1Nb alloy with dynamic recrystallized microstructure and the peak efficiency of 40% was located at the temperature range of 675-775 °C and the strain rate range of 0.001-0.01 s−1. On the other hand, flow localization and macro-surface cracking occurred within the strain rate range of 0.1-0.8 s−1. [ABSTRACT FROM AUTHOR]

Cu–9Ni–6Sn alloys have received widespread attention due to their good mechanical properties and resistance to stress relaxation in the electronic and electrical industries. The hot compression deformation behaviors of the Cu–9Ni–6Sn–0.3Mn–0.2Zn alloy were investigated using the Gleeble-3500 thermal simulator at a temperature range of 700–900 °C and a strain rate range of 0.001–1 s−1. The microstructural evolution of the Cu–9Ni–6Sn alloy during hot compression was studied by means of an optical microscope and a scanning electron microscope. The constitutive equation of hot compression of the alloy was constructed by peak flow stress, and the corresponding 3D hot processing maps were plotted. The results showed that the peak flow stress decreased with the increase in the compression temperature and the decrease in the strain rate. The hot deformation activation energy was calculated as 243.67 kJ/mol by the Arrhenius equation, and the optimum deformation parameters for the alloy were 740–760 °C and 840–900 °C with a strain rate of 0.001~0.01 s−1. According to Deform-3D finite element simulation results, the distribution of the equivalent strain field in the hot deformation samples was inhomogeneous. The alloy was more sensitive to the deformation rate than to the temperature. The simulation results can provide a guideline for the optimization of the microstructure and hot deformation parameters of the Cu–9Ni–6Sn–0.3Mn–0.2Zn alloy. [ABSTRACT FROM AUTHOR]

The effect of Ti content in various concentrations as an alloying element with Al on both microhardness and crystallization structure of aluminum–titanium alloys was studied, utilizing x-ray diffraction (XRD) and a scanning electron microscope (SEM). To study the electrochemical and corrosion performance of Al and its investigated alloys in 0.5 M solutions of HCl and H3PO4, two different techniques were used: extrapolation of Tafel plot and electrochemical impedance spectroscopy (EIS). Tafel plots and EIS revealed a similar trend. Generally, the rate of corrosion of the alloys was higher than that of Al. This investigation exhibited that the corrosion of Al alloying with Ti increased with an increase in both Ti content and temperature, which is due to reducing the growth of oxide film on the surface. Changes in the standard values of both entropy (ΔS) and enthalpy (ΔH), in addition to apparent activation energy (Ea) of corrosion processes of Al and its alloys in HCl and H3PO4, were evaluated. The evaluated data indicated negative values of ΔS, while the values of ΔH were positive. Besides, the decrease in ΔH value with the increase of Ti content in the alloy revealed that the dissolution of the studied alloys was fast. The positive values of ΔH were accompanied by an endothermic process. On the other hand, the activation energy (Ea) was decreased as a result of Al alloying with Ti in the two mentioned acids. Those results were supported by the corrosion current density (icorr.) and impedance parameters. By comparing the data obtained for both HCl and H3PO4 in all investigated electrodes, the corrosion current density (icorr.) in H3PO4 was lower than that in HCl. Such behavior can be ascribed to the aggressive attack of Cl¯ ions on the surfaces of the investigated electrodes, leading to pits formation. [ABSTRACT FROM AUTHOR]

An amount of 100 dpa Si2+ irradiation was used to study the effect of transmutation rhenium content on irradiated microscopic defects and hardening in W-xRe (x = 0, 1, 3, 5 and 10 wt.%) alloys at 550 °C. The increase in Re content could significantly refine the grain in the W-xRe alloys, and no obvious surface topography change could be found after high-dose irradiation via the scanning electron microscope (SEM). The micro defects induced by high-dose irradiation in W and W-3Re alloys were observed using a transmission electron microscope (TEM). Dislocation loops with a size larger than 10 nm could be found in both W and W-3Re alloy, but the distribution of them was different. The distribution of the dislocation loops was more uniform in pure W, while they seemed to be clustered around some locations in W-3Re alloy. Voids (~2.4 nm) were observed in W-3Re alloy, while no void was investigated in W. High-dose irradiation induced obvious hardening with the hardening rate between 75% and 155% in all W-xRe alloys, but W-3Re alloy had the lowest hardening rate (75%). The main reasons might be related to the smallest grain size in W-3Re alloy, which suppressed the formation of defect clusters and induced smaller hardening than that in other samples. [ABSTRACT FROM AUTHOR]

Titanium and its alloys (especially Ti6Al4V) are widely employed in aerospace and biomedical industry. Wire electric discharge machining is common in practice to machine this difficult-to-cut material. But owing to the thermo-electric nature of the process, it is challenging to have adequate level of surface integrity. This primary concern needs to be addressed as it mainly influences the surface mechanical characteristics. Therefore, the present research aims to address the aforesaid issues using well-known multipass strategy. Understanding the multipass process dynamics and requirements, the potentiality of brass wire diameters was comprehensively examined and explored during WEDM of Ti6Al4V. Considering higher cost, unavailability, environmental hazards, and straightness issues of novel zinc-coated wire electrodes, readily available brass wires provide a cheaper and widely acceptable solution to enhance surface integrity of machined parts if equivalent results can be somehow made possible. For that sake, three different brass wire diameters; 0.15 mm, 0.2 mm, and 0.25 mm have been considered to evaluate their impact on surface roughness, recast layer thickness, overcut, machined surface microhardness, and cutting speed using multipass cutting technique. Experimental results revealed that 0.15 mm uncoated brass wire can produce white layer result equivalent to Topas Plus X wire (Cu core-double Zn-rich layer coating) which outperformed among all zinc-coated wires used in previously published research. Moreover, among different diameter brass wires, surface roughness is improved by 25% using multipass cutting with 0.15 mm diameter in comparison to its counterparts. Scanning electron microscope (SEM) analysis depicts that the said combination reduces recast layer thickness from 39.04 µm to 14.6 µm (~ 1.5 times lesser value). In addition to that, smaller diameter (0.15 mm) provides the maximum cutting rate in rough cuts (which consume maximum machining time) and dimensional accuracy. [ABSTRACT FROM AUTHOR]

This paper presents the new route of fabrication of H-AlSi24Cu3.8Mg0.8 alloy, assisted by ultrasonic vibration stirring and squeeze casting (UVSS). The primary objective of this investigation is to establish the tribological characteristics of the prepared aluminium alloy under dry, lubricated, and coated sliding conditions. Oil SAE20W40 is used as a lubricant and diamond-like carbon (DLC) is used as a coating. Under a load between 20 N and 50 N, a linear reciprocating tribometer (LRT) with a ball-on-plate geometry is used. Alloy was examined using an optical microscope, scanning electron microscope with EDS, 3D surface profilometer, Brinell hardness tester, and tensometer for pre- and postcharacterization of alloy, surface, and worn tracks. The DLC-coated condition yields the lowest wear and coefficient of friction. [ABSTRACT FROM AUTHOR]

Soft materials such as silver, copper and Babbitt SnSb11Cu6 were deposited on the surface of tin bronze by electro spark alloying (ESA) to form the antifriction coating. The data of the antifriction coating were tested by electronic balance, three-dimensional optical profilometer, scanning electron microscope (SEM), energy dispersive spectrometer (EDS), Xray diffractometer (XRD), Vickers microhardness tester and tribometer. The mass gain, roughness, thickness, surface morphology and phase composition, cross-section and element distribution, microhardness and tribological properties of the antifriction coating were analyzed. The results show that the grain size of the antifriction coating is fine and the metallurgical bonding between the coating and the substrate is good. The surface of each substrate is composed of three layers of coating. The optimal parameters of electro spark alloying are as follows: the discharge voltages of Ag, Cu and Babbitt alloy coatings are 60 V, 60 V and 30 V respectively, the energy storage capacitance is 150 μF, 150 μF and 90 μF respectively, and the working efficiency is 3 min/cm², 3 min/cm² and 4 min/cm² respectively. Under the optimized parameters, the average mass transfer efficiency is 54.4 mg/cm², the average surface roughness is 32.3 μm, and the maximum thickness is about 160 μm. The surface friction coefficient of the soft antifriction coating is 55.6 % of that of the tin bronze substrate. The main wear mechanisms of the soft antifriction coating prepared by electro spark alloying technique are plastic deformation accompanied by slight polishing. [ABSTRACT FROM AUTHOR]

Metallic powder alloys for additive manufacturing (AM) are required to have a certain particle size and shape distribution in different processes such as laser powder bed fusion for metallic alloys (LPBF-M). For reasons of sustainability and cost-effectiveness, it is common to recycle powder that was not melted in the build construction process. As usual in a LPBF-M process, the metal powder undergoes a heuristical designed sieving and blending procedure to maintain a certain particle distribution. However, keeping track of the powder's mean age during each building cycle can be obscure or laborious. To overcome this challenge, the authors of this research propose a theoretical model and an experimental methodology to track the powder morphology evolution with respect to a specific number of building cycles and the sieved and solidified amount of powder Such morphological investigation was carried out through a scanning electron microscope, analyzing the morphological evolution of nickel-chromium alloy metal (Inconel 718) powder. The powder analysis gives a close fit of its mean age to the span of the retained particle solidity measurements and the evolution of the mean major diameter. Recycling and thereby modifying the ageing rate of the powder, under monitoring the morphologic evolution of the particles, could be considered as a key criterion for a more effective powder usage lifetime. The findings from this methodology give insight on a predictive model for aging rate, capable of retrieving information about the effective powder's lifetime, impacting positively in the organization and storage of metal powders for AM. [ABSTRACT FROM AUTHOR]

Ti-15%Zr alloy and Ti-15%Zr-2%Ta alloy were fabricated to be used in biomedical applications. The corrosion of these two alloys after being immersed in simulated body fluid for 1 h and 72 h was investigated. Different electrochemical methods, including polarization, impedance, and chronoamperometric current with time at 400 mV were employed. Also, the surface morphology and the compositions of its formed film were reported by the use of scanning electron microscope and energy dispersive X-ray. Based on the collected results, the presence of 2%Ta in the Ti-Zr alloy passivated its corrosion by minimizing its corrosion rate. The polarization curves revealed that adding Ta within the alloy increases the corrosion resistance as was confirmed by the impedance spectroscopy and current time data. The change of current versus time proved that the addition of Ta reduces the absolute current even at high anodic potential, 400 mV. The results of both electrochemical and spectroscopic methods indicated that pitting corrosion does not occur for both Ti-Zr and Ti-Zr-Ta alloys, even after their immersion in SBF solutions for 72 h. [ABSTRACT FROM AUTHOR]

Metal matrix composites (MMCs) are a special class of materials carrying combined properties that belongs to alloys and metals according to market demands. Therefore, they are used in different areas of industry, and the properties of this type of material are useful in engineering applications. Machining of such composites is of great importance to finalize the fabrication process with improved part quality. However, the process implies several challenges due to the complexity of the cutting processes and random material structure. The current study aims to examine machinability characteristics. Effects of turning a metal matrix composite built of Al2O3 sinter, saturated with an EN AC-44000 AC-AlSi11 alloy, are presented in this paper. In the present study, a turning process of new metal matrix composites was carried out to determine the state-of-the-art material for various engineering applications. During the turning process, the cutting forces, a tool's wear, and surface roughness were investigated. Further, the SEM (scanning electron microscope) analysis of cutting inserts was performed. The influence of MMC structure on the machining process and surface roughness was studied. The Al2O3 reinforcements were used in different graininess. Effects of conventional turning of the metal matrix composite with Al2O3 sinter of FEPA (Federation of European Producers of Abrasives) 046 and FEPA 100 grade were compared. Results analysis of these tests showed the necessity of continuing research on turning metal matrix composites built of an AlSi alloy and Al2O3 ceramic reinforcement. The study showed the properties of MMCs that influenced machinability. In this paper, the influence of feed rate's value on surface roughness was carried out. The significant tool wear during the turning of the MMC was proved. [ABSTRACT FROM AUTHOR]

In order to investigate the effect of stress ratio on room temperature high‐cycle fatigue life of Ti‐43.5Al‐4Nb‐1Mo‐0.1B alloy, high‐cycle fatigue life test of TNM‐TiAl alloy at stress ratio of −1, −0.5, 0.1, 0.5, 0.8, and 1 was performed on the universal testing machine. The fracture mechanism of TNM‐TiAl alloy under different stress ratios was determined by observation and analysis of microstructure and fracture surface by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and optical microscope (OM). The results show that fatigue life of TNM‐TiAl alloy with different stress ratios is mainly affected by the mean stress and stress amplitude. The fatigue life decreases with the increase of the stress amplitude and with the decrease of the mean stress. When the stress amplitude is constant, the higher the stress ratio is, the higher the mean stress in the loading process is, the lower the fatigue life is. The sensitivity of the stress amplitude of TNM‐TiAl alloy gradually increases with the increase of the stress ratio. The different cracking mechanism and fracture mechanisms at various stress ratio are revealed. Highlights: Different stress ratios affected various fatigue fracture processes of TNM‐TiAl alloy.An equal life curve was obtained to reveal the effects of different stress ratios on TNM‐TiAl alloy.Various stress ratio affects length‐width ratio of the lamellar colonies, leading to various deformation behaviors. [ABSTRACT FROM AUTHOR]

In this study, CNTs-reinforced Al-Cu-Mg-Si nanocomposites were successfully fabricated by high-energy ball milling (HEBM) combined with semi-solid stir casting. Then, the composites were subjected to hot extrusion. The Microstructure and Phase analysis of the CNT/Al-Cu-Mg-Si composites were characterized by an Optical microscope, Scanning Electron Microscope (SEM), and XRD. Additionally, density, hardness, and wear were measured. The results revealed that the addition of CNTs effectively inhibited the growth of α-Al grains, and the grains were dramatically refined. Additionally, the dynamic recrystallization degree of the composite extruded rod gradually increased from 1.3% to 68.4%, with the content of CNTs from 0 wt% to 3.0 wt%. The hardness values of the composite increased with an increase in CNTs. Moreover, the friction factor and wear rate of the composites first decreased and then increased as the content of CNTs increased. When 1.5CNTs were added, the friction coefficient (COF) and wear rate of composites reached the minimum of 0.3577 and 3.42 mg/km, which were reduced by 30.09% and 73.03% compared with Al-Cu-Mg-Si alloy, respectively. [ABSTRACT FROM AUTHOR]

Wear behavior of titanium alloys of Ti-4.5wt%Al + xFe (x: 2,4,6,8) produced by spark plasma sintering was investigated in order to highlight the effects of the iron additive on wear rate and coefficient of friction (COF). These research objectives were accomplished by a dry sliding experimental technique using the Tribometer (version 8.1.8) Anton Paar machine, which was carried out under normal loads at 10 N and 20 N with a linear speed of 0.06 cm/s. Scanning electron microscope (SEM) and X-ray diffraction (XRD) techniques were used to characterize the titanium alloy specimens. The results indicated that the wear rate increases with an increase in the applied normal load. A minimal coefficient of friction of 0.047 and a wear rate of 1.033 × 10−5 (mm3/N/M) were observed for Ti-4.5 wt% Al + 4 wt% Fe with respect to sliding at 10 N. While at a normal load of 20 N, a minimal friction coefficient of 0.015 and a wear rate of 1.74 × 10−5 (mm3/N/M) were obtained for Ti-4.5 wt% Al + 4 wt% Fe. [ABSTRACT FROM AUTHOR]

High entropy alloys (HEA) are one of the modern-era alloys accelerating with greater velocity because of their excellent properties and different applications. In the present paper, we have successfully fabricated HEA (23Fe-21Cr-18Ni-20Ti-18Mn) powders by ball milling the elemental Fe, Cr, Ni, Ti, and Mn powders for 15 h. The advancement of the milling process and phase transformation of HEAs were studied by using X-ray diffraction (XRD) and scanning electron microscope (SEM). The crystallite size and the lattice strain of the HEA were calculated by using the Williamson-Hall (W-H) equation and the values were found to be 7 nm and 0.0176%, respectively. Similarly, the true lattice parameter was calculated using the Nelson–Riley (N-R) extrapolation method, and the value was found to be 3.544 Å. We have successfully investigated the electrochemical response of 15 h ball milled 23Fe-21Cr-18Ni-20Ti-18Mn HEA powders to determine the ascorbic acid (AA) using cyclic voltammetry. We have modified the carbon paste electrode with ball milled HEA of concentrations 0, 2, 4, 6, 8, and 10 mg, and among them, 8 mg HEA modified carbon paste electrode (HEA-MCPE) depicted the highest current sensitivity. We reported the effect of modifier concentration, analyte concentration, scan rate, and pH on the oxidation peak of AA. The electrochemical active surface area of carbon paste and MCPE was calculated using the Nernst equation and the values were found to be 0.0014 cm2 and 0.0027 cm2, respectively. The fabricated HEA-MCPE showed excellent current sensitivity, stability, anti-fouling, and selectivity. [ABSTRACT FROM AUTHOR]

In this study, low-iron Zn–Fe alloy coatings and pure Zn coatings, with or without trivalent chromium passivation treatment, were electrodeposited onto a sintered NdFeB magnet from a weak acid chloride bath. The surface morphology and structure of the coatings were then examined using the X-ray diffraction, a scanning electron microscope and 3D white-light interfering surface analysis. Meanwhile, the electrodeposition behavior and anti-corrosive properties of the coatings were investigated using cyclic voltammetry, potentiodynamic polarization, electrochemical impedance spectroscopy, and natural salt spray tests. The results indicate that a passivated Zn–Fe alloy coating with a 0.9 wt.% Fe content provided much better corrosion resistance than a pure Zn coating and could provide both anodic protection and physical barrier function in the NdFeB substrates. The Fe element in Zn–Fe alloy coating was predominantly in solid solution in η-phase and small amounts in elemental form, which was beneficial to acquire a compact coating and passivation film. Finally, the passivated Zn–Fe alloy coating withstood 210 h against a neutral 3.5 wt.% NaCl salt spray without any white rust, which was 3–4 times longer than the pure Zn coating. [ABSTRACT FROM AUTHOR]

A recently developed solid-state joining technique called "friction stir spot welding" (FSSW) is used to combine metal alloys with low weldability. Significant experimental work for this study is concentrated on the FSSW of AA6063 and AA5083. The study involved fixture setup and welding pattern parameters for the sizes of the material, all of which were done on a milling machine. A cylindrical shoulder with a concave (10°) square pin profile was taken into consideration using various process parameters. The tool material is heat-treated high-carbon steel. The Taguchi L9 orthogonal array is employed for the experimental model. The influence of FSSW factors including spindle speed, time, and depth was studied, along with the relationship between tensile strength, hardness at the contact region, and hook development, which would be a nominal metallurgical pledge established in the welding zone among the interacting sheet plate. The hook structure was found in the area of contact, and thermomechanical effects were seen in the spot-welding area. It has been determined that the influencing variables are spindle speed and plunge depth. As a consequence, it was determined that a tool spindle speed of 1200 rpm, a time of 25 seconds, and a plunge depth of 0.10 mm offer better mechanical properties. The microstructural analysis of welded region was carried out using a scanning electron microscope (SEM). [ABSTRACT FROM AUTHOR]

Ti–Si–Fe alloys extracted from high-titanium blast furnace slag were utilized to replace part of the silicon powders, and then nitride/oxynitride bonded SiC ceramics were prepared by reactive sintering in graphite bed. Ti–Si–Fe alloys could react with CO/N 2 at a low temperature (1200 °C), and the addition of Ti–Si–Fe alloys could reduce the nitriding temperature of Si. Density functional theory calculations suggested that Ti–Si–Fe alloys enhanced reaction activity via weakening the strength of C O and N N bonds. The regional equilibrium phase diagrams of Si–C–N–O and Ti–Si–C–N–O under CO/N 2 atmosphere were calculated by thermodynamics. The change of whiskers morphology was observed by scanning electron microscope. Furthermore, the bulk density, the cold modulus of rupture, and the cold compressive strength improved with Ti–Si–Fe alloys content. The results showed that the addition of Ti–Si–Fe alloys not only significantly promoted nitriding of Si and formation of Si 3 N 4 whiskers, but also improved the mechanical properties of the samples. [ABSTRACT FROM AUTHOR]

For the balanced consumption of pricey rare-earth element yttrium (Y) and improved pitting corrosion resistance of alloys, Y was partially substituted by cerium (Ce) in a novel kind of quinary AlNiCoYCex high-entropy metallic glass (HE-MG) via vacuum arc melting and rapid solidification. The microstructure, thermal stability and micro-hardness of Al30Ni30Co8Y32-xCex (x = 1, 2, 3, 4, 5, and 8 at%) high-entropy metallic glass ribbons (hereafter referred to as HE-MG ribbons) have been systematically investigated. In addition, the electrochemical corrosion properties of these amorphous ribbons with different Ce content in 3.5 wt.% NaCl solution have been determined by potentiodynamic polarization and electrochemical impedance spectroscopy. After 100 h immersion in corrosive media, scanning electron microscope images of the corroded ribbons were also characterized. The results indicated that these ribbon samples could remain in an amorphous state, and the that micro-hardness was more than 495 HV0.1. With increasing Ce content, the thermal stability started to gradually increase and then decrease. Furthermore, Ce is responsible for an improvement in anticorrosion performance compared with the Ce-free alloys. Ce-containing HE-MG ribbons showed a passive region in the electrochemical reaction, and ribbons with 3 at% Ce exhibited the most corrosion resistance by virtue of the smallest Icorr and Ipass. [ABSTRACT FROM AUTHOR]

The proton irradiation-induced hardening effect of dislocations in C35M FeCrAl alloy on glide resistance was quantified by in-situ micropillar compression testing in a scanning electron microscope (SEM). Irradiation tests with a proton energy of 2 MeV were conducted at room temperature, producing plateau damage of 0.01 and 0.1 displacement per atom (dpa), respectively, and generating high density of dislocation loops with fine size (<10 nm). Single-crystal micropillars were prepared with maximizing Schmid factor for a specific slip system while minimizing the others and then compressed to active one specific slip system to measure the critical resolve shear stress (CRSS) of {110}<111> and {112}<111> slip systems, respectively. The CRSS for these two slip systems increases with increasing irradiation dose. {112}<111> slip system shows larger hardening than {110}<111> slip system. Microstructure characterization after deformation indicates that the hardening effect originates from the pinning effect of irradiation-induced defects on moving dislocations. [ABSTRACT FROM AUTHOR]

Surface modification of dental implants or orthopedic implants is important for biocompatibility, and Ti-6Al-4 V alloy is mainly used as implant material for clinical use. In particular, research on the formation of nanotubes for drug doping to improve biocompatibility is in progress. For the control of nanotube shape, in this study, nanotube shape changes on Ti-6Al-4 V alloy via various applied potential for bio-implants were researched using various instruments. The formation of nanotubes on the surface of the Ti-6Al-4 V alloy was performed using a DC power source as a two-electrode system, and platinum as a counter electrode and a working electrode as an anode. The electrolyte was 0.8 wt. % NaF solution and 1.0 M H3PO4 were used and mixed using a magnetic bar during anodization. At this time, the voltage applied when forming the nanotubes was varied as (10 → 20 → 30 V), (30 → 10 → 30 V), and (10 → 30 → 30 V), respectively, and these voltages were applied for 30 min for each step. After the formation of nanotubes, the surface morphology and structural properties of the samples were observed using field-emission scanning electron microscope, X-ray diffractometer, Fourier transform infrared spectroscopy, and nanoindentation tester. The higher the voltage applied during the formation of nanotubes, the larger is the diameter. In the case of the nanotube (10 → 20 → 30 V), the top of the nanotube was narrow and the diameter increased toward the bottom, forming a cone shape. In the case of the nanotube (30 → 10 → 30 V), a narrow waist shape was formed, and in the case of the nanotube (10 → 30 → 30 V), a jar shape was formed with anatase and rutile phases. From the FT-IR results, when nanotubes are formed, TiO2 anatase was detected and showed the tendency to change from crystallization to amorphous state. The indentation hardness and elastic modulus decreased for the nanotube surface compared with those of the bulk Ti alloy. [ABSTRACT FROM AUTHOR]

The La 0.8- x Pr x Mg 0.2 Ni 3.8 (x = 0, 0.05, 0.1, 0.2, 0.3) alloy were synthesized useing the induction melting method. X-ray diffraction, scanning electron microscope, electron probe micro analyzer, and electrochemical tests were used to analyze the structure and electrochemical performance of the La 0.8- x Pr x Mg 0.2 Ni 3.8 (x = 0–0.3) alloy. It was studied how the Pr element affected the electrochemical characteristics and microstructure of the A 5 B 19 La-Mg-Ni based hydrogen storage alloy. The results show that the alloy consists of the CaCu 5 -LaNi 5 phase, 2 H-Pr 5 Co 19 phase, and 3R-Ce 5 Co 19 phase. The abundance of the A 5 B 19 phase increase with the increase of Pr content, while the abundance of the LaNi 5 phase decrease, and the addition of Pr promotes the formation of the 2 H-Pr 5 Co 19 phase. According to the results of the electrochemical test, every sample has good activation qualities, and the activation can be completed in 3–4 times. The activation properties are not significantly altered by the addition of Pr. The maximum discharge capacity increases at first, then decreases, reaching the highest 371.15 mAh g−1 at x = 0.2. The cyclic stability gradually improves with increasing content of Pr, and the maximum capacity retention rate reaches 85.80 % after 100 cycles. The primary factor influencing the alloy's high rate discharge ability is the exchange current density. With the increase of the exchange current density, the high rate discharge performance is gradually enhanced. • The La-Mg-Ni based hydrogen storage alloy A 5 B 19 has better performance than AB 3 and A 2 B 7. • The hydrogen storage alloy was partially substituted by Pr element with higher electronegativity. • The addition of Pr significantly improves the phase structure stability and cycle stability of the alloy. • The corrosion and oxidation of the alloy electrode during the cycle are improved. [ABSTRACT FROM AUTHOR]

The effects of La and Y on the microstructure and mechanical properties of cast Al-Si-Cu alloys were investigated by X-ray diffractometer (XRD), optical microscope (OM), and scanning electron microscope (SEM). The results indicated that the addition of La and Y had a great effect on the refinement of α-Al grains, the modification of eutectic Si phase, and the reduction of β-Al5FeSi length in Al-Si-Cu alloys. The A380 + 0.6 wt.% La/Y alloy exhibited the best microstructure and mechanical properties. The UTS and EI of the A380 + 0.6 wt.% La/Y alloy were 215.3 MPa and 5.1%, which were 22.9% and 37.8% higher than those of the matrix alloy, respectively. In addition, neither Al11La3 nor Al3Y generated by the addition of La and Y could not serve as the nucleation core of α-Al grains, so the grain refinement of α-Al originated from the growth limitation and constitutional supercooling. Since La and Y promote twinning generation and constitutional supercooling, the eutectic Si phase also changed from stripe-like to short fibrous or even granular and was significantly refined. Furthermore, thermodynamic calculations indicated that the Al11La3 phase was formed first and the Al3Y phase was generated on the Al11La3 phase. [ABSTRACT FROM AUTHOR]

High-cycle fatigue (HCF) is a critical property of metastable β Ti alloys in aerospace applications. In this work, the HCF behavior and corresponding microscale deformation mechanisms of a metastable Ti-5Al-5Mo-5V-1Cr-1Fe (Ti55511) alloy with a basket-weave structure were investigated. HCF and its deformation mechanisms of a Ti55511 alloy were systematically studied in the deformed condition by using a scanning electron microscope (SEM), a transmission electron microscope (TEM), and electron backscatter diffraction (EBSD). It was found that the Ti55511 alloy exhibited an excellent HCF strength (107 cycles, Kt = 1, R = 0.06) of 738 MPa. The fractographic investigation demonstrated that fatigue striations and secondary cracks were the main features in the crack initiation zone. Dislocation analyses indicated that the HCF deformation of the basket-weave microstructure was mainly affected by the dislocation slipping of the primary α (αp) phase. In addition, the dislocation pile-up at the αp/βtrans interface led to crack initiation. EBSD analyses indicated that the prismatic type slip system of the αp phase was preferentially activated during the HCF deformation process of the Ti55511 alloy, followed by the basal type and pyramid type systems. [ABSTRACT FROM AUTHOR]

In recent years, Mg alloys have attracted increased attention for biomedical application owing to their good biodegradability, biocompatibility, and biomechanical properties. However, rapid corrosion is still one of the most common limitations for their implanted application. In this work, the microstructure and corrosion behavior of the solution- and aging-treated Mg-xGd-1Zn-0.4Zr (x = 3, 6, and 9 wt%, denoted as GZ31K, GZ61K, and GZ91K, respectively) alloys were studied using optical microscope (OM), scanning electron microscope (SEM), immersion tests, electrochemical tests, and quasi in situ corrosion method. The results show that block Gd-rich precipitates and needle-like Zr-Zn-rich precipitates are formed as well as α-Mg matrix. With the increase in Gd content, the precipitates increase and the grain size first reduces and then increases. Corrosion experiment results show that the GZ61K alloy has the best corrosion resistance and the GZ91K alloy shows the highest corrosion rate among the three alloys in simulated body fluid (SBF). It is found that α-Mg is preferentially corroded and the precipitates have better corrosion resistance as compared to the α-Mg matrix. The GZ61K alloy with the corrosion rate of 0.23 mm/y in SBF shows a promising prospect for biomedical application. [ABSTRACT FROM AUTHOR]

The main objective of this investigation is to analyze the microstructure, tensile properties, and impact toughness of Ti6Al4V alloy joints developed using optimized parameters of linear friction welding (LFW) for gas turbine blisk assembly applications. The 6 mm thick plates of Ti6Al4V alloy were joined using a friction time of 40 sec, a friction pressure of 20 MPa, a forging pressure of 10 MPa, a forging time of 3 sec, and an oscillating frequency of 14 Hz. The different regions of joints were analyzed using a stereo zoom microscope. Optical and scanning electron microscope (SEM) was used for analysing the microstructural features of joints. The room temperature tensile properties, hardness, and impact toughness of LFW-Ti6Al4V alloy joints were evaluated and correlated to the microstructural features of weld region. The fractured sections of tensile and impact toughness specimens of joints were analyzed using SEM and the failure of joints was correlated with the hardness survey. Results showed that the LFW-Ti6Al4V alloy joints developed using the optimized parameters exhibited a tensile strength (TS) of 1015 MPa, a yield strength (YS) of 940 MPa, and an elongation (EL) of 8%. The joints revealed 98.54%, 95.91%, and 66.67% of tensile strength, yield strength, and ductility of the parent metal. The LFW joints disclosed impact toughness (IT) of 17.2 J which is 89.77% impact toughness of the parent metal. The superior tensile properties and impact toughness of LFW-Ti6Al4V alloy joints are mainly attributed to a greater degree of refinement of α + β grains in the weld interface, which offers greater resistance to tensile deformation and crack propagation. [ABSTRACT FROM AUTHOR]

In the present work, the effect of thermal cycles on the physical and thermal properties of AZ31 alloy and AZ31/5wt%SiC and AZ31/10wt%SiC composites was investigated. Samples were prepared using the stir casting method and then subjected to precipitation hardening. Thermal cycles were done for as-cast and aged samples with V-shaped notch under 300, 600, and 900 heating and cooling cycles at 150 and 350 °C. The crack length (CL) was evaluated using optical microscope (OM), scanning electron microscope (SEM), and energy-dispersive scanning electron (EDS) analysis. Also, density, porosity, thermal expansion coefficient of the samples were evaluated. X-ray diffraction (XRD) analysis was employed to assess the phases present in the material. The results demonstrated that by increasing the number of thermal cycles up to 600 at 150 °C and 350 °C, the porosity and density of the as-cast and aged AZ31 alloy decreased and increased, respectively; however, the density and open porosity were remained constant for the composite samples. The crack's length enlarged with increasing the thermal cycles from 300 to 600 µm at 150 °C and 300 to 900 µm at 350 °C. It was found that the reinforcement and precipitates prevented the rapid growth of the crack in the magnesium matrix. All in All, composite and the aged samples demonstrated better thermal fatigue resistance compared with that of the unreinforced alloy and as-cast samples, respectively. [ABSTRACT FROM AUTHOR]

The paper aimed to increase the corrosion‐resistant performance of AA7075 alloy by the incorporation of sol–gel with plasma electrolytic oxidation (PEO) technologies. The AA7075 alloy substrate was first coated by an oxide ceramic layer with the help of the PEO process and then covered by a sol–gel‐derived SiO2 layer. The results from an X‐ray diffraction and scanning electron microscope clearly show that a layer of sol–gel‐derived SiO2 uniformly covered and sealed the surface microporous structure of PEO coatings on AA7075 alloy, effectively enhancing the corrosion‐resistant performance of PEO‐coated AA7075 alloy in an aqueous solution containing 3.5‐wt.% NaCl. The lower current density of 2.09 × 10−7 A/cm2 and the larger polarization resistance of 5.35 × 104 Ω cm2 were found for sol–gel/PEO‐coated AA7075 alloy as compared with 3.68 × 10−6 A/cm2 and 9.81 × 103 Ω cm2 for individual PEO‐coated AA7075 alloy. Thus, it is an effective strategy to improve the corrosion‐resistant performance of the AA7075 alloy by combining the PEO and sol–gel techniques. [ABSTRACT FROM AUTHOR]

In order to investigate the effect of Si content on the microstructures and properties of directionally solidified (DS) Fe-B alloy, a scanning electron microscope (SEM) with an energy dispersive spectrum (EDS), and X-ray diffraction have been employed to investigate the as-cast microstructures of DS Fe-B alloy. The results show that Si can strongly refine the columnar microstructures of the DS Fe-B alloy, and the columnar grain thickness of the oriented Fe2B is reduced with the increase of Si addition. In addition, Si is mainly distributed in the ferrite matrix, almost does not dissolve in boride, and seems to segregate in the center of the columnar ferrite to cause a strong solid solution strengthening and refinement effect on the matrix, thus raising the microhardness of the matrix and bulk hardness of the DS Fe-B alloy. [ABSTRACT FROM AUTHOR]

This study investigated the microstructure, hardness, tensile and tribological behaviour of a cooling slope Al--Si--Mg alloy following ECAP and T6 heat treatment. The optical and scanning electron microscopes were applied to investigate the microstructure of the as-cast material and heattreated ECAPed Al--Si--Mg alloy. The dry sliding wear test was tested with three different loads of 10 N, 50 N, and 100 N with constant sliding speed and sliding distance at 1.0 m/s and 9000 m, respectively, using the pin-on-disc tribometer. The hardness and tensile properties were evaluated through microhardness, UTS, and YS measurement for the as-cast Al--Si--Mg alloy, both heat-treated with and without ECAPed alloys. Moreover, wear rate and COF in the Al--Si--Mg alloy with different loads were analysed and linked with microstructural and strength behaviour after the ECAP process. Meanwhile, these analyses of results were correlated with the behaviour of the as-cast Al--Si--Mg aluminium alloy and heat-treated non-ECAPed alloy. Results demonstrated that a combination of ECAP processing and T6 heat treatment improves the mechanical behaviour, while the COF and wear rate are improved at a load of 100 N. [ABSTRACT FROM AUTHOR]

In this work a new nanoscale surface marking technique, namely electron beam damage induced surface marking (EBDISM), is developed and tested for the first time on a fine-grained pure Mg surface. This technique utilizes focused high-energy electron beam of a scanning electron microscope to "burn" dense arrays of nano-scale grid patterns on the sample surface, and it is proved to be very effective for identifying and measuring localised deformation behaviours. However, the surface marking deposited by EBDISM is not permanent and it tends to deteriorate overtime. Cheap, easy to use and versatile, the EBDISM technique has a huge potential for quantitative measurement of strain field and nano-scale deformation analysis. [ABSTRACT FROM AUTHOR]

In the process of directional solidification, the degree of element segregation can be changed by altering the drawing rate to affect the phase transformation behavior of the alloy. In this paper, four kinds of MnNi alloy specimens were prepared by directional solidification at different drawing rates. The phase transformation behavior of the alloy was studied by differential scanning calorimetry (DSC), X-ray diffraction (XRD), thermal expansion analysis and dynamic mechanical analysis (DMA). The microstructure of the alloy was observed by metallographic microscope, scanning electron microscope and transmission electron microscope. The results show that the microstructure of directionally solidified MnNi alloy has the characteristics of polymorphy. There are multi-scale twins from micron to nanometer in the alloy, and their coordinated movement makes the internal friction of twins 3-6 times than that of rolled alloy. It is found that during heating, the alloy undergoes fct1→fcc phase transformation in the interdendritic spacings of Mn-poor region while fct2→fco→fcc multi-stage phase transformation occurs in Mn-rich dendrite. This multiply phase transformation behavior makes the damping capacity of directionally solidified MnNi alloy 2-6 times than that of rolled MnNi alloy in a wide temperature range. [ABSTRACT FROM AUTHOR]

FeCrMnNi high-entropy alloys prepared by vacuum induction melting were tested and characterized using an X-ray diffractometer, a scanning electron microscope, a micro hardness tester and a universal tensile tester to investigate the effects of the heat treatment temperature on the microstructure and mechanical properties of the alloys and the heat-resistant corrosion properties of FeCrMnNi alloy after annealing at 800 °C. It is a high-entropy alloy with a typical dendritic (DR) morphology. With the increase in the heat-treatment temperature, the amount of ultrafine precipitates with the BCC structure in the matrix increased; furthermore, the amount of ultrafine precipitates started to decrease at temperatures above 900 °C, and the DR structure gradually weakened. After heat treatment at temperatures above 800 °C, the alloy showed a tensile strength of 721.1 MPa and an elongation at break of 26.7%, which indicates improved strength of the alloy while maintaining good plasticity, mainly because a large amount of nanoscale particles precipitated between the DR structures and enabled fine grain strengthening. Therefore, an appropriate heat-treatment temperature helps to improve the overall mechanical properties of the high-entropy alloy. [ABSTRACT FROM AUTHOR]

Bacterial infection and stress shielding are important issues in orthopedic implants. In this study, Ag element was selected as an antibacterial agent to develop an antibacterial Ti-40Nb-10Ag alloy by spark plasma sintering (SPS). The microstructure, phase constitution, mechanical properties, microhardness, and antibacterial properties of the Ti-40Nb-10Ag sintered alloys with different sintering temperatures were systematically studied by X-ray diffraction (XRD), scanning electron microscope (SEM), microhardness tests, compressive tests, and antibacterial tests. The Ti-40Nb-10Ag alloys were mainly composed of α-Ti, β-Ti, and Ti2Ag intermetallic phases. This study shows that the change in sintering temperature affects the microstructure of the alloy, which results in changes in its microhardness, compressive strength, elastic modulus, and antibacterial properties. At the sintering temperature of 975 °C, good metallurgical bonding was developed on the surface of the alloy, which led to excellent microhardness, compressive strength, elastic modulus, and antibacterial ability with an antibacterial rate of 95.6%. In conclusion, the Ti-40Nb-10Ag alloy prepared by SPS at 975 °C is ideal and effective for orthopedic implant. [ABSTRACT FROM AUTHOR]

As promising substitutes for Cu-Be alloys, Cu-Ni-Si series alloys have been investigated intensively concerning their mechanical and electrical properties but without much attention on their corrosion performance. Herein corrosion behaviors and mechanisms of the supersaturated and peak-aged CuNiSiCr alloys are investigated using salt spray test, x-ray diffraction, scanning and transmission electron microscopes. The corrosion rate of the aged sample is lower than that of the supersaturated one due to forming a denser protective corrosion product, Cu2O. Theoretical analyses indicate that the Cu2O film grows by oxidization of the matrix and its granular size is greatly influenced by the precipitates. The second corrosion product Cu2(OH)3Cl/CuCl2·3Cu(OH)2 forms by consuming the oxide Cu2O, which will induce pitting and deteriorate the corrosion resistance. Based on the obtained results, guidance concerning the composition and treatment optimization is provided for enhancing the anti-corrosion capability of the CuNiSiCr alloys. [ABSTRACT FROM AUTHOR]

A novel aluminum matrix composites (AMCs) reinforced by multiphase intermetallic compounds were fabricated through a conventional casting approach. The microstructure, compression properties and tribological behavior of the AMCs were detailed studied by the scanning electron microscope (SEM), x-ray diffraction (XRD), and electron probe microanalysis (EPMA). The results demonstrated that the fraction of precipitated multiphase intermetallic compounds gradually increased with the increase of high-entropy alloy (HEA) adding content, and the grain size of α-Al obviously was reduced. The irregular multiphase intermetallic compounds, such as Al70Cr20Ni10 and AlTiCrSi, are distributed in the Al matrix. However, the Al2Cu and Al7Cu4Ni distributed in inter-dendrites of α-Al. In addition, the compression strength of AMCs reinforced by 20.0 wt.% HEA addition was significantly enhanced to 530 MPa due to the precipitation of multiphase intermetallic compounds. Meanwhile, its compression strain was higher than 25%. Compared with pure Al, the microhardness of AMCs was extremely increased to 160 HV when the addition content of HEA was up to 20.0 wt.%. When the addition amount of HEA reached 10.0 wt.%, the COF of the ACMs was decreased by 51.6% from 0.766 to 0.371. When the HEA content was up to 20.0 wt.%, the wear rate reached the minimum of 4.87 × 10−5 mm3/N·m, which was reduced by 31.9% compared with pure Al. Furthermore, the strengthening effect and wear mechanism of AMCs reinforced by HEA addition was also discussed. [ABSTRACT FROM AUTHOR]

Calcium phosphate chemical conversion coatings with the additions of sodium lauryl sulfate (SLS) and dodecanesulfonic acid sodium (DSS), respectively, were prepared on the surface of the Mg-8Li alloy. The surface and cross-sectional corrosion morphologies, compositions, and corrosion behavior of the coated surfaces in 3.5 wt.% NaCl solution were respectively investigated by using a scanning electron microscope (SEM), energy dispersive spectrometer (EDS), electrochemical workstation, hydrogen evolution apparatus, and optical microscope (OM). The results demonstrated that Ca-P coatings had a petal-like structure being composed of leaf-like particles. After being respectively performed for 30 min in conversion solutions containing SLS and DSS, the corresponding average film thicknesses of surface coatings were 27 μm and 7 μm. In addition, the corrosion current densities of coated surfaces by using the conversion solutions containing SLS and DSS were 1.438 × 10−5 A·cm−2 and 4.719 × 10−5 A·cm−2, respectively. The effect of surfactants on phosphate chemical conversion coating was discussed in detail. [ABSTRACT FROM AUTHOR]

A complex concentrated noble alloy (CCNA) of equiatomic composition (Ag20Pd20Pt20Cu20Ni20–20 at. %) was studied as a potential high—performance material. The equiatomic composition was used so that this alloy could be classified in the subgroup of high—entropy alloys (HEA). The alloy was prepared by induction melting at atmospheric pressure, using high purity elements. The degree of metastability of the cast state was estimated on the basis of changes in the microstructure during annealing at high temperatures in a protective atmosphere of argon. Characterisation of the metallographically prepared samples was performed using a scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS), differential scanning calorimetry (DSC), and X–ray diffraction (XRD). Observation shows that the microstructure of the CCNA is in a very metastable state and multiphase, consisting of a continuous base of dendritic solidification—a matrix with an interdendritic region without other microstructural components and complex spheres. A model of the probable flow of metastable solidification of the studied alloy was proposed, based on the separation of L—melts into L1 (rich in Ni) and L2 (rich in Ag). The phenomenon of liquid phase separation in the considered CCNA is based on the monotectic reaction in the Ag−Ni system. [ABSTRACT FROM AUTHOR]

The phase structure and microstructure of Sm12Co88−xCux (x = 0, 2, 4, 6, 8, 10; at.%) as-cast alloys and melt-spun ribbons prepared via the arc-melting method and melt-spun technology were studied experimentally by X-ray diffraction (XRD) and scanning electron microscope (SEM) with energy dispersive spectroscopy (EDS). The results reveal that the Sm12Co88−xCux (x = 0) as-cast alloy contains Sm2Co17 and Sm5Co19 phases, while the Sm12Co88−xCux (x = 2) as-cast alloy is composed of Sm2Co17, Sm2Co7 and Sm(Co, Cu)5 phases. Sm2Co17 and Sm(Co, Cu)5 phases are detected in Sm12Co88−xCux (x = 4, 6, 8, 10) as-cast alloys. Meanwhile, Sm12Co88−xCux ribbons show a single SmCo7 phase, which is still formed in the ribbons annealed at 1023 K for one hour. After annealed at 1123 K for two hours, cooled slowly down to 673 K at 0.5 K/min and then kept for four hours, the ribbons are composed of Sm2Co17 and Sm(Co, Cu)5 phases. The magnetic measurements of Sm12Co88−xCux ribbons were performed by vibrating sample magnetometer (VSM). The results exhibit that the maximum magnetic energy product ((BH)max), the coercivity (Hcj) and the remanence (Br) of the Sm12Co88−xCux ribbons increase generally with the increase in Cu substitution. In particular, the magnetic properties of the ribbons annealed at 1123 K and 673 K increase significantly with the increase in Cu substitution, resulting from the increase in the volume fraction of the formed Sm(Co, Cu)5 phase after heat treatment. [ABSTRACT FROM AUTHOR]

Device-related infection or inflammatory and stress shield are still the main problems faced by titanium alloy implants for long-term implantation application; therefore, it is of great significance to design an alloy with low elastic modulus and good antibacterial properties as well as good biocompatibility. In this paper, Ti-13Nb-13Zr-xCu(x = 3, 7 wt.%) alloys were designed and prepared to reveal the influence of Cu content on the elastic modulus and antibacterial property. X-ray diffractometer, metallographic microscope, scanning electron microscope, and transmission electron microscope were used to study the phase transformation, microstructure, mechanical properties, antibacterial properties, and cytotoxicity of the alloys. The experimental results have demonstrated that the antibacterial performance and the elastic modulus were significantly improved but the corrosion resistance deteriorated with the increase of the copper content. Ti-13Nb-13Zr-3Cu with a low modulus of 73 GPa and an antibacterial rate of over 90% against Staphylococcus aureus (S. aureus) exhibited great potential as a candidate for implant titanium in the future. [ABSTRACT FROM AUTHOR]

The topologically close-packed (TCP) μ phase is usually known as an undesirable precipitation in highly alloyed Ni-base superalloys and steels. However, the ultrastrong μ phase with micron/nano-scale distribution plays a key role in driving the emergence of self-sharpening in our recently developed WMoFeNi high-entropy alloy (HEA). Herein, a detailed study is carried out to understand the substructure and atomic occupation of the μphase by scanning electron microscope (SEM) and aberration-corrected transmission electron microscope (ACTEM). The Fe/Ni and W/Mo element pairs are equivalent in the μ phase structure. Moreover, the elements in μ phase exhibit a near-equiatomic ratio, and the μ phase can grow during annealing at 1150 °C. (0001)μ and ( 1 1 ¯ 02 )μ twins are the main substructures of the μ phase, and their atomic configurations and twinning mechanisms are investigated. The geometrical structural analysis of μ phase possesses a great significance for the design of self-sharpening HEAs. [ABSTRACT FROM AUTHOR]

Aluminium alloys have low density and good mechanical properties, making them suitable for the manufacture of mechanical structures where low weight is critical. However, when these alloys are subjected to elevated temperatures, their mechanical properties deteriorate significantly. The aim of this study is to investigate the effect of temperature on the mechanical properties of aluminium alloy, EN AC-Al Si12CuNiMg. For this purpose, an experimental investigation was performed at ambient and elevated temperatures on aluminium alloy samples prepared by casting. Tensile and hardness tests were carried out to characterize the mechanical properties of this material. Additionally, an optical microscope was used to examine the microstructures of this alloy. Finally, a scanning electron microscope was used to analyze the fracture modes of this material. The results show that the mechanical properties such as tensile strength, yield strength, and Young's modulus of this alloy dramatically decrease when the temperature exceeds 250oC. The microstructural investigation reveals several factors that are detrimental to the mechanical properties of this alloy. This includes coarse-grained structures, micro-pores, and several intermetallic compounds. Furthermore, fractography reveals a minor cleavage-like pattern and micro-cracks on the fracture surface of all failed samples under various temperatures, indicating semi-brittle fracture mode. [ABSTRACT FROM AUTHOR]

This work aimed to investigate the effects of some Bi additions (x = 0, 1, 3, and 5 wt%) added to Sn–2Cu solder alloy on its thermal properties, mechanical performance, and resistance to corrosion, which was investigated by using the Differential scanning calorimetry, Scanning electron microscope, Vickers Hardness Tester, Universal testing machine, Electrochemical workstation, and X-ray diffraction. The experimental results showed that doping 5 wt% Bi could reduce the melting point from 239.7 to 226.6 °C and the undercooling from 24.0 to 9.0 °C, which could improve the thermal properties. Moreover, the Bi addition could refine the microstructure and decrease the Cu6Sn5 IMC phases' size. With the addition of 5 wt% Bi, the microhardness and tensile strength reached the highest value of 20.13 HV and 57.64 MPa, respectively, due to the solid solution strengthening and precipitation strengthening. The electrochemical corrosion behaviors were performed to use the potentiodynamic polarization and electrochemical impedance spectroscopy. The obtained results revealed that a dense passivation film was formed on the surface of Sn–2Cu–1Bi alloy to prevent the alloy from being further corroded, which had the lowest value of corrosion current density (0.034 μA·cm−2) and biggest value of total resistance (200.4 kΩ·cm2). Therefore, the Sn–2Cu–1Bi alloy had best corrosion resistance. [ABSTRACT FROM AUTHOR]

The effects of Ag content and hot-rolling on the microstructure and mechanical properties of Zn-1.5Cu-xAg-0.1Zr(x = 0, 0.1, 0.5, 1.0) alloys were investigated. The microstructure, phase composition and fracture morphology of the alloys were observed and analyzed by optical microscope, x-ray diffraction, scanning electron microscope, energy dispersive spectrometer and universal mechanical testing machine. The results show that Ag has the effect of grain refinement. After alloying, the grain size of as-cast Zn-1.5Cu-xAg-0.1Zr alloy decreased first and then increased, and the minimum grain size of as-cast Zn-1.5Cu-0.5Ag-0.1Zr alloy was refined to 64.18 μm. At the same time, new phase AgZn3 began to precipitate, the yield strength (YS), ultimate tensile strength (UTS), and elongation (EL) of alloys were also up to 97.35 MPa, 139.25 MPa and 7.60%, respectively. After hot-rolling, the grain of Zn-1.5Cu-xAg-0.1Zr alloy was broken and new phase CuZn5 was precipitated. The mechanical properties were significantly improved, and the maximum YS, UTS and EL of as-rolled Zn-1.5Cu-1.0Ag-0.1Zr alloy were 218.14MPa, 244.83MPa, 64.50%, respectively. [ABSTRACT FROM AUTHOR]

High-entropy alloys are a new generation of materials that have attracted the interest of numerous scientists because of their unusual properties. It seems interesting to use these alloys in biomedical applications. However, for this purpose, the basic condition of corrosion resistance must be fulfilled. In this article, selected corrosion properties of self-composed high-entropy alloys are investigated and compared with conventional biomedical alloys, that is titanium alloys and stainless steels. Corrosive parameters were determined using the potentiodynamic method. X-ray diffraction studies were performed to characterize the crystal structures. Microstructures of the prepared materials were examined using a scanning electron microscope, and surface hardness was measured by the Vickers method. The results show that investigated high-entropy alloys are characterized by simple structures. Three out of four tested high-entropy alloys had better corrosion properties than conventional implant alloys used in medicine. The Al0.7CoCrFeNi alloy was characterized by a corrosion potential of −224 mV and a corrosion current density of 0.9 μA/cm2; CoCrFeNiCu by −210 mV and 1.1 μA/cm2; TiAlFeCoNi by −435 mV and 4.6 μA/cm2; and Mn0.5TiCuAlCr by −253 mV and 1.3 μA/cm2, respectively. Therefore, the proposed high-entropy alloys can be considered as potential materials for biomedical applications, but this requires more studies to confirm their biocompatibility. [ABSTRACT FROM AUTHOR]

The resistance of the Al0.5Cr0.9FeNi2.5V0.2 high-entropy alloy (HEA) to hydrogen embrittlement (HE) was investigated by a slow strain rate test (SSRT), and the fracture surface was examined through a scanning electron microscope. Compared with other high-strength steels, Al0.5Cr0.9FeNi2.5V0.2 showed insignificant strength loss after hydrogen charging. The fracture surface of the hydrogen-charged specimens mainly consisted of dimples, and no intergranular morphology was observed. The coupling effect of the dispersed nano-structured precipitates and high-density dislocations in Al0.5Cr0.9FeNi2.5V0.2 improves the resistance to hydrogen-induced strength loss. [ABSTRACT FROM AUTHOR]

Recent investigations have highlighted the multi-resolution and high throughput characteristics of the spherical indentation experimental and analysis protocols. In the present work, we further demonstrate the capabilities of these protocols for reliably extracting indentation stress-strain (ISS) responses from the microscale constituents as well as the bulk scale of dual phase materials exhibiting bimodal microstructures. Specifically, we focus on bimodal microstructures produced in an α–β Ti6242 sample. Combining the multi-resolution indentation responses with microstructural statistics gathered from the segmentation of back-scattered electron images from the scanning electron microscope allowed for a critical experimental evaluation of the commonly utilized Rule of Mixtures based composite model for the elastic stiffness and plastic yield strength of the sample. The indentation and image analyses protocols described in this paper offer novel research avenues for the systematic development and critical experimental validation of composite material models. [ABSTRACT FROM AUTHOR]

Nimonic alloy 75, a high strength temperature resistant material, has widespread applications in gas turbine engines, industrial furnaces, nuclear engineering, etc. This paper presents a comparative study of capabilities evaluation between the conventional electrical discharge machining (EDM) and ultrasonic-assisted-electrical discharge machining (UAEDM) of Nimonic alloy 75 work material. During experimentation, input parameters namely tool material; discharge current; servo voltage and pulse on duration were varied to find their effects on material removal rate (MRR) and surface roughness (SR). Results indicated that UAEDM process leads to an increase of 53.57% in MRR over conventional EDM process, whereas SR of UAEDM process is 18.47% higher compared to conventional EDM process. Scanning electron microscope 'SEM' images shows that UAEDM process has fewer surface irregularities compared to conventional EDM process. Energy-dispersive x-ray (EDS) test has shown tool material migration and carbon enrichment of EDMed and UAEDMed surfaces. X-ray diffraction 'XRD' analysis has shown the formation of NiC phase on EDMed and UAEDMed surface when compared to unmachined surface. Further, a significant reduction in crystallite size was observed for EDMed and UAEDMed surface in comparison to unmachined surface. The surface microhardness increased after conventional EDM and UAEDM process as compared to unmachined surface. [ABSTRACT FROM AUTHOR]