Higher Hardness Values Research Articles

Characterization of Mixtures Based on High-Density Polyethylene and Plasticized Starch

This paper presents the obtaining and characterization of blends based on high-density polyethylene (HDPE) and plasticized starch. In addition to plasticized starch (28.8% w/w), the compositions made also contained other ingredients, such as polyethylene-graft-maleic anhydride as a compatibilizer, ethylene propylene terpolymer elastomer, cross-linking agents, and nanoclay. Plasticized starch contains 68.6% w/w potato starch, 29.4% w/w glycerin, and 2% w/w anhydrous citric acid. Blends based on HDPE and plasticized starch were made in a Brabender Plasti-Corder internal mixer at 160 °C, and plates for testing were obtained using the compression method. Thermal analyses indicate an increase in the crystallization degree of the HDPE after the addition of plasticized starch. SEM micrographs indicate that blends are compatibilized, with the plasticized starch being well dispersed as droplets in the HDPE matrix. Samples show high hardness values (62–65° ShD), good tensile strength values (14.88–17.02 N/mm2), and Charpy impact strength values (1.08–2.27 kJ/m2 on notched samples, and 7.96–20.29 kJ/m2 on unnotched samples). After 72 h of water immersion at room temperature, mixtures containing a compatibilizer had a mass variation below 1% and water absorption values below 1.7%. Upon increasing the water immersion temperature to 80 °C, the sample without the compatibilizer showed a mass reduction of −2.23%, indicating the dissolution of the plasticized starch in the water. The samples containing the compatibilizer had a mass variation of max 8.33% and a water absorption of max 5.02%. After toluene immersion for 72 h at room temperature, mass variation was below 8%.

The effect of multi-step cycles on the surface properties of Ni-TiO2 coatings produced by pulse current electrodeposition

ABSTRACT In this study, the Ni-TiO2 coatings were deposited on copper substrates by pulse plating. The effect of multi-step current cycles on the metallurgical properties of produced coatings was investigated. The results showed that the values of applied currents within the periods significantly affect the surface properties of all coatings. Using the negative current cycles, the surface morphologies completely changed from regular and compact to irregular, compared to the deposits that did not have a negative cycle in the coating process. Also, the surface roughness increased by 1.5 times in the best case. Applying the 8-step cycle increased the percentage of TiO2 content inside the Ni-TiO2 layer from 13.13 vol.% to 31.58%. The corrosion and wear analysis results showed that the coating applied by a 4-step cycle with a 90-second off time has the best properties. Therefore, the corrosion and wear properties were not necessarily directly related to the participation percentage of TiO2 particles. Compact morphology with high current efficiency, wide distribution of TiO2 particles (6.31 vol.%) with minimal agglomeration, low coating roughness (Ra = 0.32 µm), high hardness value (436 Vickers), and the participation of (111) plane in the preferred texture improved the corrosion and wear behaviour of the optimal coating.

Evaluation of water quality and heavy metal contamination in Cauvery River: Tamil Nadu region India

Abstract Comprehensive water quality control is a fundamental requirement for environmental preservation and the sustainable development of communities around the globe. To showcase the importance of local quality controls in identifying the sources of pollution, a case study was conducted to analyze the quality of drinking water from different locations along the Cauvery River from Mettur to Trichy (200 km) in Tamil Nadu, India. The quality of water samples from different locations was indexed and compared with the World Health Organization and Indian Standards of water quality. The results indicate some high local values of TDS, hardness, and chloride content. These high values may be due to effluents from industries, dying factories, and sewage from the urban areas on the banks of the Cauvery River. This is most prevalent near Mohanur, where industrial waste and effluents were directly linked into the river. The results emphasize the importance of local quality control for accurately pinpointing the factors affecting the environment.

Investigation of the effect of current density and ZrO2 bath concentration on electrodeposited Ni-P/ZrO2 composite coatings

In this study, Ni-P/ZrO2 nanocomposite coatings were deposited on St-37 steel substrates using the electroplating method with varying ZrO2 concentrations and current densities. To investigate the effects of electrolyte components and current density on coating properties, analyses were performed regarding microhardness, wear performance, and surface morphology. As a result of the analyses, it is observed that different bath concentrations and current densities significantly affect properties such as morphology, hardness, and wear performance. It is seen that the surface morphologies of the obtained coatings are generally smooth, but it is understood from the optical images that the surfaces of all nanocomposite coatings are rougher. While adding ZrO2 nanoparticles to the main matrix increases microhardness by approximately 40% compared to pure nickel, a similar but higher hardness value was obtained with the increase in current density. When examined in terms of wear performance, an average friction coefficient value of 3.15 times higher than that of pure nickel nanocomposite coatings was obtained.

Double-Chamber Underwater Thruster Diaphragm with Flexible Displacement Detection Function.

The purpose of this paper is to develop a self-detecting diaphragm integrated with a flexible sensor, which is utilized in an underwater thruster. Resistive strain sensors are easy to manufacture and integrate due to their advantages in reliable stretchability and ductility. Inspired by the structure of neurons, we fabricated resistive flexible sensors using silica gel as the matrix with carbon black and carbon nanotubes as additives. All fabricated sensors demonstrated positive resistance characteristics under 60% strain conditions, with the sensor containing a mass ratio of 9 wt % carbon black and carbon nanotubes exhibiting the best resistance-strain linearity. To verify the anti-interference capability of sensors with silica gel substrates of varying hardness values under changing environmental pressure, we tested the pressure sensitivity of the sensors by altering the hardness of the silica gel. The results indicate that silica gel with the highest hardness value provides the best resistance to environmental pressure interference. To detect the motion and deformation of the internal functional components of the thruster, we combined strain detection with the movement operation function of a silica gel diaphragm, resulting in a new integrated diaphragm with sensor detection capabilities. The integrated diaphragm was evaluated by using a tensile testing machine and an LCR tester. The results demonstrate that the mechanical properties of the diaphragm are stable, exhibiting reliable resistance characteristics and a sensitive response during underwater operation. This research can also be applied to the detection of motion amplitudes of other types of soft robots.

Enhanced Anti-Corrosion and Biological Performance of Plasma-Sprayed Nb/ZrO2/HA Coatings on ZK60 Mg Alloy

Niobium (Nb) and zirconium dioxide (ZrO2) were doped into hydroxyapatite (HA) to fabricate HA-based composite coatings prepared on a ZK60 magnesium alloy by plasma spraying technology to improve anti-corrosion and biocompatibility for clinical applications. The results revealed that the Nb-enriched coating exhibits fewer cracks and pores with a flat surface due to the decreased temperature gradient during spraying, and small needle-like structures can fill the cracks and pores in the ZrO2-contained coating, resulting in a more uniform and dense surface. Compared to coatings with only niobium or zirconium dioxide, the ZrO2/Nb/HA composite coating significantly enhanced the mechanical properties and corrosion resistance of the magnesium alloys. Among all the specimens, the ZrO2/HA coating and ZrO2/Nb/HA coating revealed high surface hardness values (327.73 HV and 293.80 HV, respectively). However, the higher hardness value made the ZrO2/HA coating fragile and more likely to crack, while the ZrO2/Nb/HA coating avoided this shortcoming and exhibited a more comprehensive performance. During immersion tests, the ZrO2/Nb/HA coating exhibited a gradual pH increase and minimal mass loss, and the cytocompatibility test demonstrated promising cellular activity.

The effect of pulverized glass waste particle sizes on the mechanical properties of AA6061-T6 friction stir welded joints.

Abstract The study sought to investigate the effect of pulverized glass waste (PGW) particle size as reinforcement for AA6061-T6 joints produced by Friction Stir Welding. The study utilized three particle sizes of 15 microns, 45 microns and 75 microns of the PGW as reinforcement alongside the established process parameters ranges of 900-1400rpm, 25-63mm/min and 1-2.5° in a Taguchi L9 orthogonal array for the welding process experimental design. The welding experiments were repeated for each reinforcement particle size mentioned above. Parallel-hole reinforcement strategy was used on all joints for the application of the PGW, Tensile strength, Hardness tests and Microstructural Analysis were carried out on the welded joints and subsequently, analysis of the data. For tensile strength, several sample sets showed a trend of higher tensile strength the smaller the PGW particles size (Figure 6). For hardness, however, there was no overall, discernable trend/pattern of increase in hardness as the particle size decreased. The highest average tensile strength value obtained was 85.25MPa. The lowest tensile strength was 14.26MPa. A distinguishing feature between the highest and lowest value for tensile strength is that the former was obtained with a traverse speed of 25 mm/min while the latter was obtained using a 40 mm/min traverse speed. The higher the rotational speed of the tool pin, the greater the heat of friction generated while the lower the traverse/welding speed, the greater the heat of friction generated as the tool pin spends enough time per unit length to generate sufficient heat and cause plastic deformation sufficiently high enough to cause grain refinement. Using imageJ, percentage distribution of PGW for each crucial zone (Nugget/Stir zone, Thermo mechanically affected zone and Heat affected zone) of the FSWed joint was generated for samples selected for microstructural analysis. The average value for each sample was obtained as well. The highest tensile strength value (85.25MPa) was obtained with a sample using the smallest PGW size (15 µm), in line with the trend (figure 6) in which tensile strength was greater the smaller the PGW size used. The highest hardness value (90.90 BHN) was obtained with the sample having the highest average value for percentage distribution of the PGW (58.06%). A distinct trend was noted in which the greater the percentage distribution of the PGW, the higher the hardness value obtained (figure 30).

Microstructure of ternary Sn-Bi-xCu alloy on mechanical properties, current endurance and corrosion morphology via cycling corrosion test

Low melting temperature of Sn-58 wt.% Bi (SB) solders adding 0.5wt.% Cu (SB05C) and 1.7wt.% Cu (SB17C) concentrations were evaluated for the signal transmission in the 3D IC package. Microstructure combined with phase analysis and Pandat simulation were together with to explain the relationship among the mechanical property, electrical endurance and corrosion resistance. By Cu decoration, the presence Cu6Sn5 intermetallic compound (IMC) acts as heterogeneous nucleation sites to reduce surface free energy and generate fine Bi grain that resulted in higher hardness value. The power-law was used to explain the mechanism of interfacial IMC growth, both Cu6Sn5 and Cu3Sn formation were speculated to be volume diffusion control and surface reaction domination, respectively. The fracture morphology by shear testing indicates that earliest plastic deformation accompanied with brittle rupture were major factors due to the intergranular fracture and Cu6Sn5 compound induced bulk fracture. By cycling corrosion test (CCT), the lump shape of SnO2 by-product was found among solders at three cycling. After seven cycling, Sn phase has been completely corroded and Cu6Sn5 IMC began to be corroded forming circle shape of Cu2O but Bi phase still not be corroded among solders. In the electrical endurance, dense Cu6Sn5 dispersed in solder bulk and fine grain size were feasible to induce current crowding and joule heating, thus Cu deteriorated SB solders is easily failed.

Synthesis, characterization, anxiolytic and anticonvulsant activity, DFT, molecular docking, DMPK studies of chalcone derived from maleic anhydride

Anxiety typically doesn't cause convulsions, but intense stress can reduce the threshold for convulsive bouts in predisposed individuals. Chalcones are known to act directly on the central nervous system (CNS) and the presence of electron donor and acceptor groups attached to the aromatic rings in various positions can alter the properties of the molecule. Thus, this work investigated the anxiolytic and anticonvulsant potential of the new chalcone derivative (E)-6-(4-((E)-3-(3-nitrophenyl)acryloyl)phenyl)-5-oxohex-2-enoic acid (CAMEL). 1H and 13C NMR and ATR-FTIR analyses helped to determine the molecular structure of this chalcone. The energy gap analysis and the higher hardness values than the softness values confirm the stability of CAMEL, with CGDRs indicating that it is more electrophilic in nature. In relation to its potential anxiolytic effect, the tested dose of 40 mg kg-1 of the derivative showed behavior like Diazepam, with activity via GABAA. In addition, the derivative also exhibited a possible anticonvulsant effect at the dose of 20 mg kg-1, being like Diazepam, showing involvement in stages 2 and 3 of GABAA receptors in this process. Given the anxiolytic and anticonvulsant activity shown in vivo and in silico tests, CAMEL is a promising candidate for the treatment of diseases that affect the CNS.

Enhancing corrosion fatigue performance of 17-4 PH stainless steel by simultaneous aging and plasma nitriding

This study investigated the effects of simultaneous aging and low-temperature plasma nitriding on the corrosion fatigue performance of 17-4 PH stainless steel. Plasma nitriding was conducted under two temperatures of 400 and 500 °C and, for comparison, some other specimens were subjected to aging treatment at the same temperatures and times. Microstructural characterization by scanning electron microscope (FESEM) and electron backscatter diffraction (EBSD) confirmed similar structures at the core in the nitrided and aged specimens, thereby, the influence of nitrogen at the surface of 17-4 alloy could be carefully investigated. X-ray diffraction and grazing incidence X-ray diffraction (GIXRD) identified expanded martensite as the matrix within the nitrided layer, accompanied by CrN, Fe3N, and Fe4N phases. X-ray photoelectron spectroscopy (XPS) analysis revealed high nitrogen concentration, in regions very close to the surface, after nitriding at 500 °C. The N1s spectra shifted towards lower binding energies, indicating interaction between nitrogen and the matrix atoms, and the formation of nitrides in the nitrided layer. The nitrided thicknesses experienced close values at 400 °C (10 h) and 500 °C (5 h), provided at 400 °C the layer was mostly a supersaturated solid solution but at 500 °C it was composed of iron nitrides and chromium nitride. High hardness values of above 1600 HV0.1 were obtained after optimum plasma nitriding as the result of combined effects of solution strengthening induced by nitrogen atoms and the presence of dispersed nitride phases. EBSD results indicated residual stress within the nitrided layer, which would affect the corrosion fatigue resistance. Experimental findings demonstrated that both aging and plasma nitriding substantially enhanced the corrosion fatigue resistance of 17-4 PH stainless steel in 3.5 wt% NaCl. Moreover, simultaneous aging and plasma nitriding proved superior behavior in corrosion fatigue, primarily due to delayed crack initiation and improved fatigue resistance, without the risk of overaging which is detrimental to mechanical properties.

COMPARATIVE EVALUATION OF HARDNESS AND SURFACE ROUGHNESS AFTER DIFFERENT COOLING PROCEDURES OF HEAT CURE DENTURE BASE MATERIALS

Aim: To evaluate the influence of different cooling procedures on mechanical properties of DPI & LUCITONE heat cure poly methyl methacrylate denturebase materials before andafter 1year of brushing simulation. Materials And Methods: A total of 100 specimens were prepared using two heat cure denture base materials i.e, DPI and LUCITONE. The specimens in each group were subdivided into five groups (n=10 ) based on the cooling procedure followed: A: Flask remains in water bath till room temperature B: Remove flask from water bath, bench cool for 30min and then cool under running water for 15min C: Remove flask from water bath, bench cool for 10min and then cool under running water for 15min D: Remove flask from water bath and bench cool till room temperature E: Remove the flask from water bath and cool under running water for 15 minutes.After finishing and polishing, samples were placed in a brushing machine to simulate one year of mechanical cleansing. The specimens were tested for surface roughness with profilometer and hardness with Vickers hardness tester before and after brushing. Results were statistically analysed by two and one- way Analysis of variance (ANOVA) plus Tukey post hoc tests. Results: Specimens with type C(Remove flask from water bath, bench cool for 10min and then cool under running water for 15min)cooling procedures have high hardness values, among whichLucitone showed better properties. Surface roughness did not show significant changes among different groups. Brushing did not significantly affect surface roughness and hardness of denture base materials. Conclusion: Two of the treatments tested, Treatment C: bench-cooling for 10 min and cooling under running water for 15min and Treatment A: cooling in water-bath till room temperature provided the highest hardness values.

Physical and textural properties and sensory acceptability of wheat bread partially incorporated with unripe non-commercial banana cultivars

Abstract Unripe banana flour (UBF) is recognised as a functional ingredient because of its nutritional pattern. The influence of substituting wheat flour with unripe non-commercial banana (Luvhele and Mabonde) flours on bread’s physical and textural properties and sensory acceptability was evaluated. Wheat flour was replaced with 2.5, 5, 7.5, and 10% of UBF of Luvhele and Mabonde in bread production. Physical properties such as volume, density, weight, colour, and textural characteristics were determined. Furthermore, a sensory evaluation of the bread was performed. The inclusion of UBF of Luvhele and Mabonde cultivars significantly decreased (P ≤ 0.05) the weight, volume, and specific volume of breads, but a higher density of breads was observed. Breads containing 10% UBF had the highest hardness values (9.92, Luvhele, and 9.96 N, Mabonde). However, breads incorporated with UBF of both banana cultivars had lower chewiness, cohesiveness, and springiness than control bread. The control bread had crumbs and crust that were significantly lighter (P ≤ 0.05) than the crumb of composite breads. Sensory evaluation results showed that bread incorporated with up to 7.5% UBF of both banana cultivars was acceptable in terms of aroma, taste, and overall acceptability.

Pengaruh Variasi Bahan Aditif Pada Base Quench Medium dan Holding Time Tempering Terhadap Sifat Mekanik Material Roda Gigi

Gears are one of the most important components in various machine systems, and in their use, the gears rub and press against each other with other components, so they often experience wear on their surfaces. Therefore, to overcome these problems, the gear material is given a hardening and tempering heat treatment to improve its mechanical properties. The purpose of this study was to determine the effect of variations in cooling media in the quenching process and tempering holding time on the hardness value and impact strength of S45C steel. The method used is S45C steel heated at 950°C for 35 minutes, then cooled using water + 0.12% activated carbon, a 5% NaCl solution, and SAE 15 W 40 oil + 0.12% activated carbon. After that, it was tempered at 260 °C for 15 minutes, 25 minutes, and 35 minutes. Then a hardness test was carried out to determine the hardness value, and an impact test was carried out to determine the toughness value. From the results of the study, it was found that the optimum parameters for overcoming wear problems on gears were using water + 0.12% activated carbon cooling media and a tempering holding time of 15 minutes. From these optimum parameters, it produces a high hardness value of 36.3 HRC and an impact price of 0.23 J/mm².

Influence of aging temperature on the microstructure and mechanical properties of a Cu-2Be alloy

As a contribution to existing knowledge, this work studied the evolution of the hardness, elastic modulus and microstructure of an age-hardenable Cu-2Be alloy when subjected to aging treatments at different times, in order to obtain the hardness curves at all stages, and for different aging temperatures in the range of 320–400 °C. In addition, the effect of performing a prior heat treatment consisting of 2 h at 225 °C on the mechanical behavior of the material was analyzed. The elastic modulus and hardness were measured using IET technique and Vickers hardness, respectively. The best mechanical properties (higher hardness values and high elastic modulus) were obtained for treatments at aging temperatures of 320 and 350 °C, with aging times of 40 and 5 h, respectively. The maximum hardness decreases with temperature and increases by about 25 HV by performing a prior thermal treatment at 225 °C. At the maximum hardness peaks, the elastic modulus exhibits similar values, while the asymptotic value increases slightly with temperature. SAXS measurements were used to study the size and shape of the nanoprecipitates formed after aging treatments at different temperatures and times. At the hardness peaks, precipitates have ellipsoid shapes and their size increases with the temperature from 18 to 30 nm. After the hardness peak at 400 °C, the hardness and modulus decrease slightly, while the precipitate size increases to 58 nm.

Low-Calorie Cookies Enhanced with Fish Oil-Based Nano-ingredients for Health-Conscious Consumers.

This study explored the effectiveness of fish oil (FO)-loaded nanoemulsions, averaging 197 nm in diameter, as fat substitutes in creating low-calorie cookies. The cookies' diameter, thickness, and spread ratio were measured, ranging from 46.33 to 57.15 mm, 6.45 to 7.51 mm, and 6.16 to 8.86, respectively. Notably, cookies containing nanoemulsions exhibited a significant increase in the spread ratio compared to the control. The control sample had the highest hardness value at 43.81 N, while the nanoemulsion group had the lowest at 26.98 N. The energy value, which was 508 kcal/100 g in the control group, decreased to 442 kcal/100 g in the group containing the nanoemulsion. The total n-3 fatty acid content in cookies rose from 0.46% in the control cookies to 3.90% in the cookies containing nanoemulsion. Sensory evaluations showed that cookies containing fish ol-loaded nanoemulsion received the highest scores, indicating that the fat reduction did not compromise the desired ″greasy″ sensation. This is especially noteworthy, as it showed that the fat content could be reduced by half without compromising the sensory quality. Utilizing FO-loaded nanoemulsions as a fat replacement in fat-reduced baked goods could provide valuable insights for other food products. The findings have significant implications for the food industry, suggesting that healthier, low-calorie baked goods can be developed without sacrificing physical quality and texture. This approach can cater to the growing market demand for health-conscious food options, potentially leading to new product innovations and enhanced nutritional profiles in a variety of food products.

Optimization of Iron Oxide (Fe2O3) Addition Parameters on the Physical Properties of Al-Si Alloys as an Advanced Material Innovation

Aluminum-silicon alloys are widely used in the industrial world, one of which is because they have high wear resistance. The aim of this research is to determine the physical and mechanical properties of the Al-Si alloy after strengthening by mixing reinforcing materials. The research method uses Taguchi optimization and analysis of the physical properties of the Al-Si alloy test results. The results showed that the highest hardness value was obtained in the 7th experiment, namely with a rotation variation of 2000 rpm, temperature of 6000C, and holding time of 60 seconds. This result is in line with the results of the tensile strength test, where the highest tensile strength was also obtained in the 7th experiment. This result is supported by the results of other researchers, which show that the higher the rotation in the casting results in higher hardness. The results of the microphotographs show that all alloy materials have an even distribution of grains, the grain size appears small, and the dendrites in the raw Al-Si alloy appear small compared to other materials. The macro photo results show that all alloy materials have fractures that appear brittle, as evidenced by the fact that these fractures provide light reflection.

Additively manufactured carbon fiber reinforced-polyamide component: a study based on statistical modeling and regression analysis

This paper presents the experimental assessment of the hardness characteristic of additively manufactured polyamide (PA 6) composite reinforced with carbon micro-fibers. The carbon fiber-reinforced polyamide (CFPA) components were manufactured using the additive manufacturing technique—fused deposition modeling (FDM). The experiments were conducted for testing the hardness of the samples using a Shore-D hardness tester. The novel contributions of the work towards the manufacturing fraternity include selecting a scantly researched material like CFPA, and the elaborative investigation of hardness variation with the alteration of the prime parameters pertaining to FDM. The effect of the print-related parameters, namely, layer height (LH), infill density (ID), and raster orientation (RO) on the hardness of the CFPA component was studied, and the results were analyzed using statistical analysis tool ‘analysis of variance (ANOVA)’. Moreover, a regression model was developed to predict the output response, i.e. hardness for different combinations of the input parameters. Considering an ID of 100% and an RO of 0°, the hardness value of 93.89 at 0.1 mm LH reduced to 88.44 at 0.3 mm LH, depicting a reduction of 5.81%. An increasing trend was observed for hardness with the increase in ID for all the levels of LH and RO. The highest value of hardness (93.89) was achieved at an ID of 100%, with the LH and RO values kept at 0.1 mm and 0°, respectively. The ANOVA suggested that the effect of all three parameters is significant in the study, ID being the most affecting parameter with an effect contribution of 37.88%. The fitness of the adopted model was well justified by the high R-sq value of 0.9618 and significantly low error values in the range of 0.002–0.08.

The microstructure and mechanical properties of the laser-welded joints of as-hot rolled AlCoCrFeNi2.1 high entropy alloy

AlCoCrFeNi2.1 hot-rolled eutectic high entropy alloys were welded by laser welding, yielding a free-defect laser-welded connection. With the use of optical microscopy, EDS, EBSD, and XRD, the microstructure of the base metal (BM), fusion zone (FZ), and heat-affected zone (HAZ) of the joint was examined. The produced joint underwent tensile and micro-hardness testing as well as a fracture morphology examination. A similar tensile strength in the FZ and BM is measured, while a decrease in the elongation. The typical layered lamellar structures, in particular an FCC + BCC dual-phase structure, were all visible in the HAZ, BM, and FZ zones. The α-fiber and γ-fiber as well as other textures are determined by the ODF figure, indicating a potential orientation distribution of the as-hot rolled AlCoCrFeNi2.1 joint. A clear grain refinement characteristics in the fusion zone as a result of the uneven thermal cycling during the welding process. The results of the mechanical test demonstrate the base metal has the highest hardness value, i.e. 500–550 HV0.2, within the welded joint zone. The welded joint has a tensile strength ∼1200 MPa, which is marginally higher than ∼1150 MPa in the base metal, and an elongation that decreases by 20 % from base metal to welded joint, indicating a decrease in the plasticity of the welded joint. A combination of brittle and ductile fracture occurs in welded joints during tensile failure. This study may give possibilities for the engineering application of laser welding of AlCoCrFeNi2.1 eutectic high entropy alloy in the future.

Graphene nanoplatelet reinforced Al-based composites prepared from recycled powders via mechanical alloying and pressureless sintering

This study reports on the powder metallurgy preparation and characterization of aluminum-graphene nanoplatelet (Al-GNP) composites synthesized using recycled Al powders. Recycled Al and GNP powders (0.1–1 wt%) were mechanically alloyed (MA'd) for 4 h, followed by cold pressing (at 450 MPa) and pressureless sintering at 590 °C for 2 h. Starting powders were analyzed using an optical emission spectrometer (OES) and a Raman spectrometer. Also, MA'd powders and sintered samples were characterized using an X-ray diffractometer (XRD), a scanning electron microscope/energy dispersive spectrometer (SEM/EDS), and a differential scanning calorimeter (DSC). Particle size analyses, pycnometer, and Archimedes' densities, Vickers microhardness, dry-sliding wear, and compression tests were also conducted. The Al4C3 formation was observed in the XRD patterns of sintered compositions. The highest and lowest relative densities were measured for the 1 wt% and 0.1 wt% GNP reinforced samples as 97 % and 92 %, respectively. The highest hardness value was obtained as approximately 1.31 GPa for 1 wt% GNP reinforced. With the addition of reinforcement GNP, the wear rate developed to approximately 0.00225 mm3/Nm. The compressive strength increased from nearly 70 MPa to 162 MPa.

Comparison of the hardness value and microstructure of Al6061 in horizontal centrifugal casting with and without mold cooling

The object of this research is the horizontal centrifugal casting process of the Al6061 alloy. Usually, cast products experience some casting defects, so the horizontal centrifugal casting process is applied to reduce the possibility of casting defects arising. In some casting processes, especially in the production of cylindrical specimens, casting defects such as porosity are encountered. Therefore, horizontal centrifugal casting was applied to overcome this problem. The test results show that the average hardness value for aluminum 6061 specimens resulting from centrifugal casting products with water cooling was 73.3 HRE, while the average hardness value for aluminum 6061 specimens resulting from centrifugal casting products without water cooling was 86.4 HRE. The microstructure results show that the grain size of centrifugal casting products with water cooling was 82.5 µm, whereas without water cooling it was 75 µm. Higher hardness values were obtained in specimens without mold cooling, this is because the conductivity in molds without cooling was higher compared to molds that experienced water cooling. The higher the heat conductivity of the mold, the faster the cooling process of the cast product. The casting process using the horizontal centrifugal method can be carried out to produce cylindrical spare parts