https://www.metalleng.ir/ Metallurgical Engineering en daily 1 Tue, 14 Nov 2023 00:00:00 +0330 Tue, 14 Nov 2023 00:00:00 +0330 https://www.metalleng.ir/article_708890.html In this study, the hot deformation behavior of Ti6Al4V alloy with an equiaxed microstructure (alpha/beta) was investigated using the Zener–Hollomon parameter and processing maps. Firstly, the stress-strain curves were derived from the hot compression tests, which were conducted at temperatures of 800 to 950°C and strain rates ranging from 10-3 to 1 s-1. Following the determination of the constants of the constitutive equations (ln A, α, n and Q) by using experimental flow curves, predicted flow curves were plotted. On the other hand, microstructural examinations and hardness tests were performed to reveal the microstructural changes and the heterogeneity index. The SimuFact-Forming (FEM) software was also used to simulate stress and strain distributions and dimensional changes in the test samples, as well as force-displacement curves during the hot compression tests. Based on the comparison results, it can be concluded that the hyperbolic sine equation provides more accurate approximations of the Zener-Hollomon parameter and the flow stress. According to the processing maps, the highest power dissipation efficiency was observed within the temperature range of 900 to 950 °C and the strain rate range of 0.3 to 1. Moreover, the unstable zones of processing map were indicated at low temperatures and strain rates (the temperatures between 800 and 840 °C within a strain rate of 10-3 to 0.03). The results showed that the force-displacement curves obtained from finite element simulations were in good agreement with those obtained from experiments. https://www.metalleng.ir/article_709325.html In this study the effect of sulfuric acid baking process on the leaching behavior of the sulfide concentrates of Sungun copper mines was investigated. The effect of temperature and time of baking and weight ratio of acid to concentrate were studied. The response surface method (RSM) with 3 factors in 5 levels (temperatures of 170, 200, 215, 230 and 260 ℃, times of 30, 90, 120, 150 and 210 minutes and the weight ratio of acid to concentrate of 0.5, 1.5, 2, 2.5 and 3.5) was used in experimental design of baking process. The baked products were leached at distilled water in constant temperature of 60 ℃ for 45 minutes with solid to liquid ratio of 30 g/L. The maximum copper leaching efficiency of 96% was obtained under the following baking conditions: 230 ℃ of baking temperature, 90 min of baking time and 2.5 of the weight ratio of acid to concentrate. The RSM model predicted the maximum copper leaching efficiency of 97% for baked concentrates at 205 ℃ for 177 min. with acid to concentrate ratio of 2.1, which it was confirmed by experiment. Also, the phase analysis using XRD patterns confirmed the converting of insoluble chalcopyrite to water soluble sulfates during acid baking process and showed the elemental sulfur in baked products and leaching residues. https://www.metalleng.ir/article_709543.html In this research, the effect of cold rolling percent on the microstructure and shape memory effect (SME) of an Fe-9.5Ni-6.5 Mn (wt.%) alloy was investigated. Experimental results such as X-ray diffraction (XRD) and electron backscatter diffraction (EBSD) analyses revealed that the microstructure of the initial alloy in the solution annealed condition was a fully lath -martensite with a high density of dislocation. Under cold rolling with 60 and 90% reductions in thickness, the austenite () phase with a fine grain size was partially induced in the martensite matrix through a shear  transformation, resulting in the development of a dual-phase () steel. Strain-induced austenite inherited the dislocation structure from the parent martensite due to have a shear nature. In addition, the volume fraction of the induced austenite in the microstructure of the initial alloy increased by increasing the rolling percent. The tensile test results indicated a maximum shape recovery of 35% at 1% pre-strain for the 90% cold rolled specimen. Also, the observation of strain hysteresis in the cyclic stress-strain curve of the cold rolled specimen by 90% confirmed the presence of the pseudoelastic behavior for this sample. The presence of austenite phase with high density of dislocation in the dual-phase steel was the main reason for appearance the SME and pseudoelastic behavior. https://www.metalleng.ir/article_709656.html In this research, the effect of pulsed Nd:YAG laser welding variables, including pulse energy, frequency and welding speed, on the depth and width of Nimonic 75 with a thickness of 1 mm is investigated. The microstructure of the weld contains columnar grains in the border and coaxial grains in the center of the weld. At the welding boundary, the thermal gradient (G) is higher and the grains grow against the direction of heat transfer. Liquidation crack is one of the welding defects in Nimonic 75, which is caused by the presence of brittle phases of MC carbides such as TiC and also thermal stresses. By increasing the pulse time width and frequency, the average power and overlapping of pulses have been increased to reduce the temperature gradient and thus reduce the thermal stress on the weld. The microhardness in the weld was higher than the base metal and its value is different across the weld due to the change in microstructure. Liquidation cracks were observed in all the worked and heat-treated samples. By reducing the thermal stresses and performing the preheating process in all the tests, the length of the melting cracks decreased compared to the initial base plate. The preheating operation at 150 degrees Celsius removed the liquidation cracks. https://www.metalleng.ir/article_720027.html The main novelty of this research study is established on the consolidation of Ti-6Al-4V titanium alloy matrix nanocomposite with incorporation of 1.5 wt% bone nanoparticles using additive manufacturing (AM) technology based on the selective laser melting (SLM) procedure, for the means of biomedical implant and bone tissue engineering applications. A wide range of SLM processing parameters were examined and the working window for manufacturing of such an advanced material was optimized, by density measurements and elaborating the different cross-sections of the constructed structures using the microscopy techniques. To this end, the leading results revealed a diminishing trend for the porosity and surface roughness of the SLM-manufactured components by increasing the energy density, attributing the laser power increasing along with the laser scanning speed and hatching space decreasing. Also, in comparison between the SLM additively manufactured Ti-6Al-4V alloy and Ti-6Al-4V/1.5 wt% nanocomposite, introducing of the bone nanoparticles made the structure of material more porous (14.4% up to 28.3%), while such a reduction in the part’s integrity resulted in the elastic modulus drop from 44.7 GPa down to 26.9 GPa. https://www.metalleng.ir/article_710338.html This research examines the effect of laser single layer coating process parameters including laser power, scanning speed and powder feeding rate on the geometrical characteristics of the layer (width, height, depth of penetration and fusion) by mathematical and experimental models. The powder used is NiCoCrAlY, which is coated on a substrate of nickel base CMSX-4 superalloy by laser coating process. In order to optimize the parameters and reduce the time spent in repeating the process , Statistical-experimental modeling of single-pass freezing geometry and microstructure was done using response surface method and linear regression analysis. The results showed that the predicted values correspond to the measured values. This review confirms the effectiveness of the models obtained from the regression analysis. Finally, the relationship between the main process parameters and geometrical characteristics were studied. Statistical modeling showed that there is a linear relationship between the geometrical characteristics of single-pass coating and the main parameters of the process. The correlation coefficient for all obtained equations was more than 0.9. The modeling results showed that the laser power has a direct effect on all the geometric features, While the powder feeding rate only affects the thickness and has a negative effect on the width and depth of penetration of the coating layer, The scanning speed has a negative effect .The optimal parameters of the process obtained from the response surface method are the laser power of 850 W, the scanning speed of 15 mm/s and the powder feeding rate of 4 g/min. https://www.metalleng.ir/article_711309.html In recent years, research activities in the improvement and development of high entropy alloys in non-equiatomic compositional space have been expanded by manipulating deformation mechanisms. In this research, a type of high entropy steel with TWIP behavior has been designed. To further advance production techniques and investigate the hot deformation behavior of this steel, hot compression tests have been carried out in the temperature range of 950-1100˚C and the strain rate of 0.001-1 s-1 to the true strain level of 0.5 The results of the microstructural studies obtained from the hot compression test showed the occurrence of partial recrystallization in most deformation conditions. The appearance of flow curves in the test conditions also confirms the sluggish recrystallization compared to other common austenitic steels. By evaluating the recrystallization mechanisms, it was found that the discontinuous recrystallization mechanism as the dominant mechanism and the continuous recrystallization as the auxiliary mechanism control the microstructural evolutions. Moreover, the higher recrystallized grains fraction by increasing the temperature and strain rate was attributed to more storage energy and rising temperature due to adiabatic heating. Finally, according to the constitutive calculations, the activation energy at the strain of 0.4 for this steel was obtained as 536.1 kJ mol-1. https://www.metalleng.ir/article_711324.html Hybrid composites provide a combination of properties such as tensile modulus, compressive strength and wear resistance, which cannot be obtained in ordinary composite materials. Usaully, these composites involves of one or two ex-situ and in-situ reinforce particles. In this study, the hybrid composite AZ91/Mg2Si/5wt%SiCP with micron-sized SiC particles was selected and, 1 and 2wt% nano-sized SiC were added to this composite. The present study investigated the effect of bimodal size SiC particles on the microstructure, mechanical, and wear properties of the cast and extruded composites and compared to the composites with micron-sized SiC reinforcement and base alloy. The present of Mg2Si and nano-sized of SiC particles had positive influence on the microstructure refinement and decrement of the grain size. The results show that the adding of 1 and 2wt% nano-sized SiCp significantly improved the microstructure, mechanical properties and wear resistance of the AZ91 alloy after hot extrusion. Using a less amounts of micro particles along with nano particles is a proper choice to improve mechanical properties and wear resistance. https://www.metalleng.ir/article_711535.html Oxide ceramics are mostly bio-inert and need surface modification to increase bioactivity with the bone tissue. This study evaluates the synthesis of hybrid nanofibrous scaffolds of nylon6-hydroxyapatite on toughened alumina-zirconia implants. The Nanostructured-scaffold was created on the surface using electrospinning method. The results showed that the average fiber diameter size was 70-180 nm, the scaffold thickness was less than 500 nm, and open pores with an average size of 500 nm were formed. The thermal stability evaluation showed that the nano-scaffold had thermal stability up to 200 ℃, and the nylon6 polymer matrix practically evaporated at 300 ℃. Bioactivity was evaluated by immersion test in the simulated body fluid (SBF) over 21 days. The results confirmed the formation of a nanostructured bone-like apatite phase with the morphology of blade with a wall thickness of 34 ± 5 nm. The antibacterial activity test showed that the hybrid nanofibrous coating of nylon6-hydroxyapatite on the toughened alumina-zirconia improved the antibacterial activity by 10%. The development of such bioactive coatings paves new ways for the use of bio-inert materials in bone tissue engineering. https://www.metalleng.ir/article_711646.html In this research, the ZnO-Bi2O3-Sb2O3- based varistor ceramic was made under an electric field of 300V/cm and a current density of 100 mA/mm2 by flash sintering method, and its properties were compared with the conventionally sintered sample. The density of the flash sinter sample reached 95.6% of the theoretical density and the microstructure and phases in it were similar to the conventional sinter sample. E-J curve showed that the sintered flash sample also has nonlinear behavior and varistor properties. The value of nonlinear coefficient was obtained for flash and conventionally sintered samples, 34.4 and 41.5, respectively. Using the thermionic emission model, the potential barrier height, the width of the depletion layer, the density of donors and the surface states at the interface of grain and grain boundary were measured under DC electric field. The electrical resistance value of the grain boundary, which was measured by the electrochemical impedance method, was lower in the flash sintered sample than in the conventional sintered sample, which is due to the lack of sufficient time for ions to diffuse completely from the volume of the insulating phase to the grain boundary. The stability of the samples was investigated by measuring the current creep by applying temperature and electric field. The results showed that the current leakage in the flash sintered sample is more than the conventional sintered sample. https://www.metalleng.ir/article_711688.html In this research, a hydrophobic double layer Mg-Al LDH hydroxide coating has been synthesized on AZ31 magnesium alloy through a facile hydrothermal method followed by chemical modification by stearic acid. The characteristics of the intended coatings were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and infrared spectroscopy (FT-IR). XRD and SEM patterns showed that the LDH film surfaces were nano/micro-layered and the LDH sheets tended to grow vertically on the surface. The static contact angle (CA) was calculated for different surfaces of the samples, which was found to be around 114.4 degree. The corrosion resistance of LDH-SA hydrophobic coating was measured using electrochemical spectroscopy (EIS) and dynamic polarization (PDP) test and the equivalent circuit of the investigated system was drawn. EIS measurement and polarization curve showed that the hydrophobic coated magnesium alloy had better corrosion resistance in 3.5 wt% NaCl solution. The value of Z for the coating containing stearic acid is close to 10^5 Ω.m^2. https://www.metalleng.ir/article_713657.html The present study involved the casting and hot-rolling of steel with a chemical composition of Fe-0.25C-0.33Si-1.05Mn-4.56Al. Subsequently, heat treatment was applied at various temperatures and durations to achieve the necessary material characteristics. Initially, all of the specimens underwent austenitization at a temperature of 820 ℃, which is the annealing temperature corresponding to the midpoint of the critical range. This process lasted for a duration of 600 seconds. Subsequently, the specimens were subjected to quenching in oil at a temperature of 150 ℃, and this temperature was maintained for a period of 20 seconds. Finally, the specimens were immersed in a salt bath. The mixture, composed of equal parts NaNO3 and KNO3, was subjected to transfer and partitioning processes at temperatures of 330 and 450 ℃, and for durations of 1000 and 1800 seconds. Subsequently, the mixture was rapidly cooled by immersion in water. The microstructural composition of steel after to heat treatment encompasses the presence of δ-ferrite, α-ferrite, retained austenite, and a minor quantity of martensite. The volume fraction of the surviving austenite is shown to grow as the temperature and partitioning time are elevated. This can be attributed to the heightened driving force and increased likelihood of carbon diffusion. The sample that underwent partitioning at a temperature of 450 ℃ for a duration of 1800 seconds yielded the optimal combination of strength and elongation, resulting in a product value of 41600MPa%. The provided specimen exhibits a tensile strength of 1300 MPa and experiences a 32% elongation. https://www.metalleng.ir/article_713758.html The effect of polypropylene fibers was investigated by compression and bending tests, identification of the resulting phases by X-ray XRD diffraction pattern test and phase morphology by field microscope FE-SEM, investigation of thermal behavior and types of bonds formed by DTA-TG thermal test and FTIR was performed. The results showed that the strength increases with the increase in the storage time of the samples from 7 to 28 days. The addition of polypropylene fibers has increased the compressive strength compared to the sample without fibers. By adding 3% of 4 and 8 mm fibers, the compressive strength of 28 days increases by 46%. The XRD results showed that quartz and pyrophyllite minerals are the main remaining phases of these structures after the geopolymerization process in all samples. The FTIR results showed that in the geopolymeric samples, the CM-1 peak at 1030/63 has shifted to higher frequencies, i.e. 1528/171-1422/97 cm, which indicates the progress of the geopolymerization process. SEM images showed that the extrusion mechanism is more dominant than other mechanisms. The results show that samples containing 3% by volume of fibers have the highest compressive and bending strength and can be considered as optimal values. https://www.metalleng.ir/article_713877.html In recent decades, additive manufacturing technology or 3D printing has attracted the attention of many researchers. This manufacturing method has made it possible to directly fabricate parts of the desired design, to manufacture complex parts that were practically impossible to produce with conventional manufacturing methods, and to reduce the consumption of raw materials. Additive manufacturing has become a suitable method for manufacturing parts in both academic and industrial fields. In this research, the goal is to construct a porous kaolin substrate in order to achieve an ideal ratio of water to clay. Considering the percentage of water and raw material and printing by extrusion method, the optimum percentage is equivalent to 40% water and 60% raw material. Comparing the XRD results showed that the kaolinite phase changed to metakaolin after heating, and the scanning electron microscopy and energy-dispersive spectroscopy results showed the microstructure of kaolinite and metakaolin and its constituent elements, respectively. Also, using the Archimedes method, the density of the samples with three-dimensional structure after heat treatment was measured, which was 2.2, 2.9, 2.4, and 2.49 g/cm3 for the samples heat-treated at temperatures of 1100, 1000, 900, and 1200, respectively. https://www.metalleng.ir/article_714059.html IN738 Ni-based superalloy has high-temperature strength and suitable creep properties due to the presence of a high volume fraction of γ' phase, which is widely used in the aerospace industry, including the manufacture of gas turbine blades. In this research, welding was performed by pulsed Nd:YAG laser on IN738 sheets with a thickness of 1 mm. By changing the parameters of pulse frequency, pulse duration, and welding speed, the change of welding properties was investigated. The results of microstructural investigations with optical and electron microscopes showed that the sensitivity to melting and solidification cracks decreases with increasing pulse frequency and pulse duration, the most important cause of which is the decrease in the welding cooling rate due to the increase in heat input. Contrary to most of the research, in this research, by increasing the welding speed, the sensitivity to melting and solidification cracks decreased, the most important reason for which is the elimination of the effect of plasma on the weld pool. It was found that pulsed Nd:YAG laser with pulse frequency, pulse duration, and welding speed of 21 Hz, 7 ms, and 9 mm/s, respectively, can obtain a weld with full penetration and no cracks, and the tensile and hardness test results also confirm this issue. https://www.metalleng.ir/article_714060.html In this research, the microstructure, distribution of elements and constituent phases, of SPSed Ti-10Mo alloy were evaluated and their effect on its corrosion resistance were investigated. To prepare Ti-10Mo alloy by spark plasma sintering, 90 wt.% of powder titanium was mixed with 10 wt.% of molybdenum powder in a ball mill for 10 hours. The ratio of ball to powder were 1:10. The powder mixture were sintered at 1250˚C at pressure of 50 MPa for 6 min in a vacuum of 0.1 Pa. In the microstructure β phase and α/β structure, in which acicular α phase have grown in the grain boundaries, are seen. Analysis of open circuit potential indicated that a passive film formed spontaneously on the alloy, and due the wide passive region that can be seen on the polarization curve, would another evidence to formation of the passive film. The EIS results also confirm that the passive oxide film formed on the alloy is a bi-layer structure consisted of an outer porous layer and an inner barrier layer, in which the inner barrier layer ensures the alloy a good corrosion resistance. https://www.metalleng.ir/article_714111.html The aim of this study was to investigate the effect of martensite morphology on tensile behavior of dual phase (DP) steel. For this propose, a cold-rolled low carbon steel (0.18wt.%C and 1.25wt.% Mn) was subjected to three different heat treatment cycles with the names of intercritical annealing (IA), step quenching (SQ) and intermediate quenching (IQ). IA cycle included an isothermal annealing in the intercritical region followed by water quenching, SQ included an austenitization step followed by intercritical annealing and water quenching, and IQ included an austenitization and water quenching to obtain a fully martensitic microstructure and subsequent intercritical annealing of this martensitic microstructure to obtain a DP microstructure. According to the results, the DP steel obtained by IQ which contained fine and fibrous martensite in the ferrite matrix had the highest ultimate tensile strength, uniform and total elongation and work hardening magnitude, while the step-quenched sample which contained large and blocky martensite in the ferrite matrix had the lowest value for the mentioned properties. All the samples showed a two-stage work hardening behavior based on the Hollomon analysis. The dominant fracture mechanism for all samples was ductile fracture mode. https://www.metalleng.ir/article_714112.html In the present investigation, Al-Al2Cu composites prepared in-situ via mechanical alloying of a powder mixture containing Al and 10wt.% of two different sizes of Cu powders, cold pressing and sintering. In order to investigate the effects of chemical treatments on the microstructure and properties of composites, in a number of experiments, the as-received Cu powders treated with 15% HCl. The micro-hardness of the as-received and the milled powders as well as the micro-hardness, porosity and macro-hardness of the produced composites quantified and the microstructure of composites studied via light microscopy. The results of this investigation on the Al-Cu powder mixture before sintering as well as on the sintered composite samples revealed the positive effect of chemical treatment on enhanced micro-hardness, decreased porosity and increased macro-hardness of the samples due to more effective interaction between Al and Cu and improved distribution of the Al2Cu intermetallic within the Al matrix. In addition, in all the performed experiments, using fine instead of coarse Cu powders resulted in enhanced interaction between Al and Cu particles and improved quality of samples. https://www.metalleng.ir/article_714113.html Hypereutectic Al-Si composites due to their low density and desirable properties have attracted a great amount of interest by the automotive and aerospace industries. However, the coarse size and un-modified morphology of the primary silicon particles that usually forms during the solidification of these alloys impose negative effects on the mechanical properties of these composites. Therefore, it is necessary to choose a suitable casting and solidification technique to overcome this drawback. In the present study, the vibrating cooling slope (VCS) technique as a semi-solid casting process was employed for preparation of composites by using the hypereutectic Al-20wt.%Si ingot as the starting material. The ingot melted and superheated at 50, 70 and 100 °C and after passing a cooling slop poured into a cast iron mold. For the purpose of comparison composite samples by using the conventional cooling slope (CS) and gravity casting (GC) also prepared by applying the identical materials and superheating temperatures as the VCS samples. The effect of the superheating temperatures on the microstructure, porosity and hardness of the composites investigated. A set of samples subjected to pin-on-disc wear test. The increased superheating temperature resulted in increased size of the Si particles for all the investigated samples. The CS samples despite of their higher porosity exhibited higher hardness values as compared with their GC counterparts. Also the hardness of VCS samples was higher than their CS counterparts. The wear test results confirmed the decreased both the wear loss and friction coefficient for the VCS samples https://www.metalleng.ir/article_714114.html The unique properties of metal foams have led to the increasing use of these structures in industrial applications such as catalysts. To accurately design engineering systems and high-efficiency catalysts, it is necessary to study the fluid flow behavior. Therefore, this study aimed to investigate the effect of different geometric parameters of the porous medium on fluid flow and to present a linear regression model for predicting Forichmer equation coefficients (ΔP / L = αv + βv2) using computational fluid dynamics (CFD) and linear regression statistical method. For this purpose, in the first stage, foams based on real geometry and with different pores diameter and porosities were made by the Voronoi method. Then, using CFD simulation, the effect of foam structural parameters on fluid flow was investigated. The results indicated that the coefficients of the Forichmer equation and the pressure drop significantly depend on the geometrical parameters of the foam. In the second stage, due to the structural complexity of the foam and the high volume of the computational cost in this method, linear regression models were used to provide a continuous model based on the structural properties of the foam to model the coefficients of the Forichmer equation. The results demonstrated that the model is very accurate in predicting the coefficients of the Forichmer equation in terms of the geometric parameters of the foams. Also, the results obtained from linear regression models demonstrated that the proposed approach effectively predicts fluid flow in large-scale porous catalysts with minimal error. https://www.metalleng.ir/article_714062.html Mechanical properties of metastable austenitic stainless steels, factors controlling the strain induced martensitic transformation, the importance of transformation induced plasticity effect, and grain refinement via the reversion of martensite to austenite were summarized in this review paper. For this purpose, firstly, the formation of strain induced martensite, methods for determining the amount of strain induced martensite, and important factors affecting the kinetics of strain induced martensitic transformation such as chemical composition of the steel, initial grain size, and deformation parameters were critically discussed. After that, techniques for modeling the kinetics of strain induced martensitic transformation and mechanical properties of austenitic stainless steels were reviewed. Finally, processing of fine-grained microstructures during reversion annealing for improvement of mechanical properties was overviewed. In conclusion, this review paper is a summary of the opportunities that formation of strain induced martensite can offer for controlling the microstructure and mechanical properties of metastable austenitic stainless steels. https://www.metalleng.ir/article_715177.html This study investigates the microstructure and mechanical properties of as-cast high-entropy alloy FeCoCrNiC. The alloy was subjected to hot rolling at 1000°C and 1100°C, followed by homogenization at 1000°C for 5 hours between each rolling pass. X-ray diffraction (XRD) analysis was employed to identify the phases present, while optical microscopy (OM) and scanning electron microscopy (SEM) were used to examine microstructural changes. Microhardness testing was conducted to evaluate mechanical properties. The as-cast alloy exhibited a non-homogeneous, three-phase microstructure consisting of an FCC matrix, chromium-rich BCC regions, and graphite. This resulted in significant variations in hardness across different phases. To address this issue, a series of thermomechanical treatments were performed. The results showed that after thermomechanical processing, the graphite particles were dispersed and partially dissolved, leading to a reduction in their quantity and a more homogeneous microstructure. Consequently, the hardness values became more uniform.Keywords: High-entropy alloy, thermomechanical processing, homogenization, microstructure, microhardness. https://www.metalleng.ir/article_715281.html Conventional methods face limitations when it comes to producing near-net-shape products of high-strength advanced engineering alloys, while additive manufacturing as an alternative approach have garnered the interest of artisans and researchers. High-performance engineering materials, such as nickel-based superalloys, are specifically formulated to endure harsh conditions like elevated temperatures, extended exposure time, and corrosive surroundings. Consequently, there is a significant demand to study the high temperatures mechanical characteristics of advanced high-strength alloys produced through additive manufacturing. In this research, the high temperature flow behavior of Inconel625 superalloy produced through selective laser melting has been investigated. For this purpose, hot compression tests were performed at temperatures of 800, 900, 1000, and 1100 ℃ under the strain rates of 0.001, 0.01, and 0.1s-1. In order to modeling the flow stress behavior, modified Arrhenius-type model and artificial neural network model were employed. Standard statistical parameters in the form of correlation coefficient (R), root mean square error (RMSE) and average absolute relative error (AARE) were used to evaluate the accuracy of the developed models. Due to the significant changes in the strain rate sensitivity and deformation activation energy in the studied temperature range, Arrhenius model could not accurately predict the high temperature flow behavior. While the artificial neural network model represented high capability in modeling the hardening and softening behavior of the investigated superalloy. Based on the predicted data, power efficiency and dissipation maps were constructed at strains of 0.1, 0.2, 0.3, and 0.4, then the metallurgical instability regions and optimal deformation conditions were identified. https://www.metalleng.ir/article_715321.html In this paper, the solid-state magnetic refrigeration properties of Ni50Mn34In16-xAlx (x=0, 0.5, 1, and 1.5 at.%) was evaluated. For this purpose, bulk samples with a diameter of 8 mm were fabricated using a suction-melting system. A homogenization annealing process was carried out at 1073 K for 4 hours in a tube furnace under an Argon gas atmosphere. XRD and FE-SEM were used for structural and microstructural characterization at room temperature. DSC was employed to study the phase transformation in the temperature range of 200-375 K with a cooling rate of 10 K/min. Temperature-dependent magnetic properties were evaluated using a magnetic property measurement system (MPMS) under a constant magnetic field of 2 T at a temperature range of 175-375 K with a cooling rate of 3 K/min. Furthermore, the magnetic and magnetothermal properties were analyzed using a VSM equipped with a cooling-heating system at the magneto-structural transformation and magnetic phase transition temperature range. The results indicated that the doping of Al led to the formation of the martensite phase at ambient temperature. It was also observed that with increasing Al the characterization temperatures of the first-order phase transformation decreased. The substitution of In by Al resulted in a gradual decrease in saturation magnetization and a weakening of magnetocaloric properties. As the Al content was increased to 1.5 at. %, the saturation magnetization decreased from 49 eum/g to 8.5 eum/g, the magnetic entropy change decreased from 3.4 J/kg·K to 1.1 J/kg·K, and the refrigeration capacity reached from 109.83 J/kg to 8.1 J/kg. https://www.metalleng.ir/article_716986.html Copper is one of the most widely used industrial metals, which has a good weldability by fusion methods; but the grain growth is one of the problems that occurs in heat affected zone of this metal causing the decrease of mechanical properties of the joint. To calculate the grain growth, first of all, it is needed to fit the experimental data to mathematical models and calculate the existing parameters. In this research, the grain growth of commercially pure copper has been studied. For this purpose, the samples of copper sheet were isothermally held in furnace at the temperatures of 1123, 1173 and 1223 K for the times of 10 to 60 minutes. The average grain size was determined from the metallographic image analysis and the 2D grain size was converted to 3D grain size through the computational methods. Sellars and Anelli models were used to fit the data, and grain growth parameters were obtained for both models. The analysis of the normalized residuals showed that the mean is close to zero and they have a Gaussian distribution, and both models seem to fit reasonably to the data. Mechanical properties were measured by microhardness test and tensile test. It was observed that the relationship between hardness and yield strength with grain size follows the Hall-Patch relationship and the corresponding constants were obtained. https://www.metalleng.ir/article_720410.html The aim of this research is to fabricate polycaprolactone (PCL) and polycaprolactone/poly-pyrrole (PCL/PPy) scaffolds by electrospinning method. In order to investigate the effect of electrospinning parameters and concentration of both polycaprolactone and PPy on the morphology, wettability and electrical conductivity of electrospun scaffold the following method is done. Concentrations of PCL and PPy are selected 17, 20, 25%wt and 0, 2.5, 5 and 10%wt respectively. Also, the electrospinning is performed at different voltage (i. e. 12, 14 and 16 kV). The results indicate that increasing the concentration of polycaprolactone has increased the fiber diameter, decreased the number of beads, and changed the morphology of the beads from spherical to spindle-shaped and elongated. The lowest number of beads is observed for all samples at 14 kV voltage. Polycaprolactone scaffold with a concentration of 25%wt and a voltage of 14 kV is selected as the optimal sample and poly-pyrrole particles were added to this sample. By adding poly-pyrrole particles with a concentration of 2.5%wt, the diameter of the fibers increased, and then by increasing the concentration to 5 and 10%wt, the diameter decreased. Due to the hydrophilic nature of poly-pyrrole, increasing its concentration has improved the hydrophilicity of the scaffold. Also, by adding 5%wt of poly-pyrrole particles, the electrical conductivity of polycaprolactone fibers has increased from 1.1 × 10-12 to 4.7 × 10-9 siemens per meter. https://www.metalleng.ir/article_720470.html In this research, AZ31 alloy and AZ31 alloy reinforced with graphene oxide particles (i.e., AZ31-GO nanocomposite) were subjected to friction stir processing (FSP) and their microstructure and mechanical properties were compared. The FSP process was carried out under a constant advance speed of 85 mm/min, rotation speeds of 1180 and 1500 rpm, and shoulder diameters of 12 and 16 mm. After applying the FSP process, the grain size in the AZ31 and AZ31-GO nanocomposite samples reached from 80 micrometers to about 3.5 and 3.7 micron, respectively. Hardness in FSP samples increased by about 36% and in composite samples by about 28%, which increase in hardness can be attributed to fine graining through dynamic recrystallization, pinning of boundaries by secondary phase particles and reinforcement particles and prevention of dislocations climbing by reinforcing particles. Microstructural observations showed that increasing the rotation speed and shoulder diameter causes a homogeneous and uniform distribution of graphene oxide in the microstructure. The tensile test was performed with a strain rate of 0.05s-1. Elongation and UTS in FSP and nanocomposite sample with 12 mm shoulder diameter reached from 38.082 and 212.8686 MPa to 37.5 %, 246.9484 MPa, and 31.74 %, 257.0776 MPa, respectively. https://www.metalleng.ir/article_721299.html Cardiac stent are intracorporeal structures used to open blocked coronary arteries caused by fatty plaques or metabolic abnormalities, and they can be utilized in either temporary or permanent forms. In this study, the effect of pressure parameter in the additive bio-manufacturing process (FDM) on the loss coefficient (Tan δ) of smart polymeric stents was investigated. The objective of this research is to enhance the shape memory effect of polymeric stents without the use of plasticizers or lubricants, and without the addition of polymeric nanocomposites. The results obtained from experimental DMTA and SEM analysis indicate that pressure variation during manufacturing leads to an 18.8% reduction in the loss coefficient and enhances the shape memory effect in the range approaching the shape memory region. Additionally, the results confirm the increase in atomic Van der Waals forces and the reduction of covalent and molecular bond lengths within the structure of the memory stent. These molecular composition changes provide the memory stent with greater elasticity and an improved capacity for energy storage within the smart active range. https://www.metalleng.ir/article_714493.html In the present research, the compression method of copper powder and space holder was used to product copper foams using NaCl space holder. Copper foams were product with 60, 70 and 80 volume percentages of space holder. A comparison of the energy absorption of copper foams after the dissolution of space-forming particles and after the initial sintering process and after the final sintering process was done. The results showed that the energy absorption of foam in the method of removing the space holder after initial sintering has a significant difference compared to the method of removing the space holder after the final sintering process, so that for foam with 60% space holder by volume of 15.58 has decreased to 11.94 mega joules per cubic meter. Also, scanning electron microscope (SEM) images were used to investigate the effect of space holder dissolution on porosity and it was shown that if there is NaCl in the stage of the final sintering process and then its dissolution, it causes damage to the walls cellular. https://www.metalleng.ir/article_724799.html In this research, two dual-phase heat treatment methods- intermediate quenching and step quenching- on NiCrMoV low alloy steel were compared using microstructural analysis, Vickers hardness, and tensile test. The results demonstrated that at 760 °C, a constant intercritical temperature, the step quenching method was much faster due to the single-step process contrary to intermediate quench, which is a multi-step that causes complex microstructure, including tempered martensite and fresh martensite. According to the microstructural analysis, this method produces more martensite fraction. After 60 minutes, the hardness of the intermediate quenched sample was almost equal to that of the step-quenched sample, though it had a smaller intercritical martensite fraction. However, due to the increase in ferrite production rate compared to the intercritical martensite, the hardness of the intermediate quenched sample was decreased after 60 minutes from 338 to 287 vickers. In the step-quenched sample, no specific changes were observed by increasing the time more than 60 minutes. This issue indicated that the step-quenching process was almost completed after 60 minutes https://www.metalleng.ir/article_724866.html During the manufacturing of superalloy components, unwanted plastic deformation may occur during hot isostatic pressing and subsequent machining or grinding. High-temperature thermal cycles can increase recrystallization and reduce the alloy's mechanical properties. In this study, samples of IN738LC were subjected to plastic strains at different percentages and then exposed to thermal cycles at various temperatures. Structural investigations were conducted using optical microscopy, and the recrystallization phenomenon was studied. Tensile tests were performed at room temperature and 650°C, and stress-rupture tests were conducted under conditions of 982°C and 152 MPa on heat-treated samples. The results showed that no recrystallization of grains was observed until the annealing temperature of 1140°C; however, this phenomenon occurred at 1160°C and strains above 1 percent. At higher temperatures, recrystallized grains were observed with any level of plastic strain. The yield strength without recrystallization increased by 17%, while it decreased by 4% with recrystallization. The ultimate strength increased by 22% and 15%, respectively, and elongation increased by 9% and 66%. At 650°C, the yield strength decreased by 26% and 10%, the ultimate strength increased by 12% and 2%, and elongation decreased by 30% and 1%. The creep life and elongation without recrystallization decreased by 61% and 78%, respectively, while in the recrystallized sample, they decreased by 78% and 69%. The changes in mechanical properties can be attributed to the accumulation of dislocations and twin boundaries devoid of strengthening phase boundaries. https://www.metalleng.ir/article_729615.html In this study, the design and simulation of knee prosthesis was investigated. The presented model included femur bone, tibial head, meniscus, muscle, socket, and liner, which was first subjected to physiological loading, and based on the results, the optimization process was performed on the socket. Next, the optimized and non-optimized sockets were subjected to the same loading and the boundary conditions in order to study the effect of the optimized socket on the stress and displacement of different components of the leg prosthesis. The results demonstrated that the optimized socket reduces the equivalent stress based on von Mises throughout the leg, and slightly reduces the displacement. The intended behavior showed the effectiveness of the optimal socket in absorbing stress and protecting other organs and strengthened its use for medical applications in future. The model can be improved by including the dependence of bone material properties on density and analyzing in cyclic loadings and different forces to evaluate the behavior of the presented model in different conditions. https://www.metalleng.ir/article_729633.html Due to the increasing interest in the thermoelectric properties of materials and finding new materials that have thermoelectric applications, In this work, the structural and thermoelectric properties of Ag2SiS3 compounds with monoclinic crystal structures have been investigated using density functional theory in the LDA approximation with the quasi-potential method. In the investigation of the band structure, the value of the band gap was obtained in the approximation of LDA=1.21 eV, LDA+U=1.42 eV and HSE=2.26 eV electron volts, which is in good agreement with the work of others and has an indirect band gap between the Γ and E dots. The thermoelectric properties of the Ag2SiS3 compound were also investigated, and the value of the figure of merit ZT=1 was obtained from the measured results. It was found that the application of Hubbard and the HSE hybrid function did not have a significant effect on the value of the figure of merit, but it affected other compound properties such as thermal conductivity and electrical conductivity. The Ag2SiS3 compound is a suitable compound for thermoelectric applications. https://www.metalleng.ir/article_718388.html This work is motivated to identify newly synthesized MOF nano-catalyst via metal-organic frameworks UiO-66-Type with free carboxylic acid as an efficient MOF functionalized magnetic graphitic carbon nitride (Fe3O4/g-C3N4) via decoration of Gadolinium- Nanoparticles. In order to prepare a highly efficient catalyst UiO-66-COOH @ g-C3N4/Fe3O4 @ Gd-NPs as a heterogeneous catalyst for applying to remove Heavy Metals which have been investigated. UiO-66s with acidic sites, such as carboxylic, have been synthesized for acid catalysis and adsorptions. UiO-66 MOFs with free –COOH groups could be obtained by several methods such as direct synthesis, ligand exchange, and post-modification. For direct synthesis of UiO-66-COOH and UiO-66-(COOH)2, 1,2,4-benzene tricarboxylic acid and 1,2,4,5-benzene-tetracarboxylic acid (BTEC), respectively, were applied as the organic linker. These adsorption studies can not only suggest potential applications of the obtained MOFs but also confirm the presence of free –COOH. In this work, we still confined ourselves to the model MOF system of carboxylic acid-functionalized, Zr-based UiO-66-COOH, in the superior chemical and hydrothermal stability of UiO-66 as well as the COOH -modification-induced improvement in absorption capacity. Various techniques, including FT-IR, XRD, BET, SEM, TEM, EDS, and elemental mapping were used to characterize UiO-66-COOH @g-C3N4/Fe3O4 @ Gadolinium Nano particles, indicating its successful preparation. The results of productivity catalyst are accomplished in excellent yields under mild conditions which is a proof of superior activity heterogeneous catalyst containing Gadolinium-nanoparticles. The adsorption capacity of g-C3N4/Fe3O4/UiO-66-COOH is expected to reach a maximum of 292 mg/L, which is attributed to abundant functional groups and high surface area. https://www.metalleng.ir/article_731613.html In the zinc production Nickel are removed from zinc solution by cementation with zinc powder. The high consumption of zinc powder lead to increased production costs. Undoubtedly, increasing the speed and efficiency of the process can help improve the process. In this study, an attempt was made to produce zinc foam with a very high specific surface area by creating nanostructured zinc foam with nano-pore structure via the electrodeposition method. Zinc foam with a very high specific surface area was produced and used in the cementation process. The specific surface area of the obtained foams, which was measured by the BET method, was found to be between 8 and 480 m2/g. A kinetic study of the cementation rate was conducted with the produced foams in a non-continuous reactor by examining parameters such as temperature, time, pH, stirring speed, and Zinc stokiometry. The decrease in the concentration of the nickel over time was investigated, and the Avrami and shrinking core models were found to have a better fit with the obtained results. Ultimately, the Avrami kinetic model was proposed for this reaction. The results indicated that control is exerted by the diffusion of ions from the boundary layer. Temperature was found to increase the reaction rate, and the activation energy was calculated to be 4.7 kJ/mol. It was observed that increasing the temperature and stirring speed has an increasing effect on the Avrami exponent n, and the values of n increase from 0.82 to 0.9 and from 0.73 to 0.89, respectively https://www.metalleng.ir/article_729745.html In this research, the hot working behavior of 13.5Cr6Al0.3C high aluminum mild steel was investigated. This steel with 3% Al by weight has a higher SFE than other stainless steels, for this reason, the test of the hot pressure behavior of this steel and its microstructural changes, including recovery and recrystallization mechanisms, were investigated. According to the prediction of JMatPro software, this steel is ferritic at all temperatures and carbide deposits are formed in it. Accordingly, the hot pressure test was performed at temperatures of 850, 900, 950 and 1000 C at strain rates of 1, 0.1, 0.01 and 0.001-s. After calculating the fundamental relations of hyperbolic sine, the activation energy of silane stress for this steel was calculated as 379.84 kJ/mol. Also, the Zener-Holman equation was calculated and based on the process map of this steel, a temperature of 950°C and a strain rate of 0.1-s were reported to have the lowest activation energy. https://www.metalleng.ir/article_723211.html In this research, novel zinc-based alloys with a fixed composition of 1 wt% Mg and varying amounts of copper (Zn-1Mg-xCu) were fabricated through casting and subsequently evaluated for their corrosion properties and microstructural characteristics. Polarization and electrochemical impedance spectroscopy (EIS) tests were conducted in a specialized cell containing simulated body fluid, and corrosion current density (icorr) and corrosion potential (Ecorr) were calculated. Additionally, immersion tests in simulated body fluid were performed for durations of 24 and 168 hours, during which changes in sample weight and solution pH were measured. The results indicated that the corrosion current density increased with the addition of copper to the binary Zn-1Mg alloy. The highest corrosion current density, measuring 12.87 𝜇A/cm2, was observed in the Zn-1Mg-4Cu alloy. The corrosion potential did not exhibit a significant increase with the addition of copper across all compositions. Electrochemical impedance spectroscopy results demonstrated a decrease in corrosion resistance as the copper content increased. The Zn-1Mg-1Cu alloy exhibited the highest resistance. Higher copper content led to a larger volume fraction of Zn/Mg-Cu eutectic, decreasing the cathode-to-anode ratio and increasing corrosion. No discernible changes in sample weight or the pH of the simulated body fluid were observed after 24 hr. After 168 hours, the Zn-1Mg-4Cu alloy experienced a maximum weight loss of 103.9 mg and a pH increase to 7.8. The formation of galvanic couples between the zinc-rich dendritic matrix and the Zn/Mg-Cu eutectic phase is responsible for these changes in the corrosion properties of the ternary Zn-1Mg-xCu alloy.