Arash Fattah-alhosseini - Academia.edu (original) (raw)

Papers by Arash Fattah-alhosseini

international journal of iron and steel society of iran, 2013

This paper focused on the characterization of electrochemical behavior of a martensitic stainless... more This paper focused on the characterization of electrochemical behavior of a martensitic stainless steel in the acidic solutions. For this purpose, electrochemical parameters were derived from potentiodynamic polarization, Mott Schottky analysis and electrochemical impedance spectroscopy (EIS) techniques. The potentiodynamic polarization results showed that corrosion current density of AISI 420 stainless steel was decreased with the decrease in the concentration of solution. EIS studies also showed that as concentration was decreased, the measured value of polarization resistance was increased. This trend was due to the decrease in the corrosion current density, which corresponded to potentiodynamic polarization curves. Mott Schottky analysis revealed that passive films behaved as n-type and p-type semiconductors at potentials below and above the flat band potential, respectively. Also, Mott Schottky analysis indicated that the donor and acceptor densities were increased with solutio...

Applied Surface Science Advances, 2021

Magnesium is known as a suitable biological material because of its biocompatibility and biodegra... more Magnesium is known as a suitable biological material because of its biocompatibility and biodegradability. The most important limitation of magnesium and its alloys is their poor corrosion resistance. Having a standard electrochemical potential of-2.38 V, magnesium and its alloys are considered to be the most anodic structural metal compared to the standard hydrogen electrode. Poor corrosion performance of magnesium and its alloys has resulted in a reduction in their chemical stability as well as limited use in corrosive media. One solution to overcome this obstacle is surface modification of these alloys. A variety of coating methods have been studied to provide protection for magnesium and its alloys against corrosion, including PEO. An important parameter in this process is chemical composition of the electrolyte. Changing the condition of the electrolyte based on the presence of particles is one of the beneficial approaches to reduce the porosity of the coating and improve its final behaviors. Suitable properties of zirconia nanoparticle including great mechanical strength, good corrosion resistance in addition to antibacterial properties are the main reasons for its usage. This paper summarizes the findings of the researches on the utilization of zirconia nanoparticles in the PEO coating process of magnesium and its alloys which includes the effect of the nanoparticle on microstructure, corrosion, mechanical and tribological properties of the alloys.

Journal of Materials Research and Technology, 2021

Abstract The main aim of this study is to develop ZrN/CrN nanolayered coatings with bilayers peri... more Abstract The main aim of this study is to develop ZrN/CrN nanolayered coatings with bilayers periods 10 bilayers (10 L), 20 bilayers (20 L) and 30 bilayers (30 L) over AISI 304 stainless steel and also evaluating the effect of nanolayers architecture on their electrochemical behavior. The nanolayers were deposited from chromium and zirconium targets using the cathodic arc evaporation physical vapor deposition (Arc-PVD) technique in a nitrogen atmosphere. The nanolayer microstructure and morphology were evaluated using X-ray diffraction (XRD), atomic force microscopy (AFM), and field emission scanning electron microscopy (FE-SEM). The chemical composition was studied by energy-dispersive X-ray spectroscopy (EDS) tests. The electrochemical characterization was carried out by potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) tests in 3.5 wt. % NaCl solution in order to investigate changes in the electrochemical behavior as a function of the deposited bilayers number. The existence of CrN and ZrN phases with FCC lattices in the nanolayers were identified by the XRD patterns. The FE-SEM observations showed that the multilayered coatings were deposited at an excellent periodicity. The electrochemical tests indicated that the corrosion resistance of ZrN/CrN nanolayers is enhanced by increasing the number of bilayer periods that can be ascribed to the decrease in the pinholes and blocking the penetration path of corrosive solution.

Journal of Asian Ceramic Societies, 2020

The aim of this research is the evaluation of the influence of TiN, CrN and TiN/CrN nanostructure... more The aim of this research is the evaluation of the influence of TiN, CrN and TiN/CrN nanostructured coatings on corrosion resistance of nickel-chromium dental alloy in artificial saliva environment with two pH levels (3.0 and 6.5). Nickel-chromium alloy tested in this study were more resistant to corrosion in artificial saliva conditioning media when coated with different types of coating materials, as compared to uncoated alloy. The electrochemical measurements propose that the alloy with CrN coating has shown a high corrosion resistance in different pH levels. The superior passivation of CrN monolayer coating in modified Fusayama artificial saliva solution may be concluded from two essential factors, passive range, and corrosion current density. The passive range is well-developed, while the corrosion current density is much lower if compared to the other groups. Also, the Nyquist and polarization plots reveal that TiN, CrN and TiN/CrN nanostructured coatings have an excellent corrosion resistance which is considered much higher if compared to the substrate. The values of corrosion current density for CrN nanostructured coating in artificial saliva environment with two pH levels of 3.0 and 6.5 were 1.373 × 10 −8 and 5.416 × 10 −8 A.cm −2 , respectively that were the lowest corrosion current density values among the other samples.

Journal of Asian Ceramic Societies, 2020

Ceramics International, 2020

Corrosion Science, 2018

In the present work, the role of cold deformation and anodic potential on the electrochemical res... more In the present work, the role of cold deformation and anodic potential on the electrochemical response of pure nickel in borate buffer solutions were investigated. The application of cold deformation gave rise to a more localized microstructure that contained a greater number of fine grains. In order to investigation of the electrochemical response of specimens, potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), and Mott-Schottky (M-S) analysis were performed. As a result, with increasing of applied potential, the polarization resistance and passive film thickness decreased. Also, density of electron acceptor at passive layer decreased by increasing of applied potential.

Journal of Alloys and Compounds, 2018

Recently, high power impulse magnetron sputtering (HIPIMS) technique has been widely applied to d... more Recently, high power impulse magnetron sputtering (HIPIMS) technique has been widely applied to deposit hard coatings such as Ti-based coatings on industrial tools due to its strong merits of high coating density, smooth surface, and excellent adhesion. In this work, TiN (Titanium Nitride) nanostructured coatings were deposited by two different methods (HIPIMS and DCMS techniques) with constant processing parameters and their electrochemical behaviors were investigated in a 3.5% NaCl solution. X-ray diffraction (XRD), field emission scanning microscopy (FE-SEM), and atomic force microscopy (AFM) were used to characterize and evaluate the coatings composition, surface morphology, and surface roughness, respectively. It is found that the preferred orientation depends on the applied deposition technique. Potentiodynamic polarization measurements and electrochemical impedance spectroscopy (EIS) were used to compare the electrochemical responses of these nanostructured coatings in 3.5% NaCl solution. The results indicate that HIPIMS-TiN coating is of well-defined denser nanocrystalline structure, which not only is smoother but also has a superior passivation and better protects the substrate against the ingress of aggressive anions.

The International Journal of Advanced Manufacturing Technology, 2017

The microstructural evolution and mechanical properties of a new Al-3.8Cu-1.2Li-0.4 Mg-0.4Zn-0.4A... more The microstructural evolution and mechanical properties of a new Al-3.8Cu-1.2Li-0.4 Mg-0.4Zn-0.4Ag-0.3Mn-X alloy treated at different solution temperatures were investigated. The grain size was measured in optical micrograph (OM). The residual particles and the major precipitates were identified by electron probe microanalysis (EPMA), scanning electron microscopy (SEM) and transmission electron microscope (TEM), respectively. The results show that the peak strength appears at 530°C/1 h ? T6(165°C/20 h) and the values are 566.2 MPa (tensile strength) and 538.2 MPa (yield strength) with the elongation of 6.5 %. The strength of the alloy increases rapidly with the amount of the precipitates T 1 and h 0 increasing when the solution temperature is 530°C. The increase in density of precipitates is resulted from the residual particles Al 2 Cu, and particles enriched with Cu, Mg, Zr and Ag dissolve into matrix gradually with the solution temperature increasing. Finally, the number of precipitates decreases and part of the grain boundary weakens with a further increase in solution temperature from 540 to 550°C, leading to a decline of strength.

Journal of Alloys and Compounds, 2017

The present study investigated the influence of grain refinement on the passive and electrochemic... more The present study investigated the influence of grain refinement on the passive and electrochemical response of 2024 Al alloy in a borate buffer solution. Optical microscopy and transmission electron microscopy (TEM) micrograph depicted that with increasing the pass number of accumulative roll bonding process, the grain size of samples decreased and ultra-fine grained structure achieved. Also, the X-ray diffraction (XRD) analysis revealed that mean crystallite size decreased with increasing the number of accumulative roll bonding passes. To investigate the electrochemical behavior, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and Mott-Schottky (M-S) analysis was carried out. Potentiodynamic polarization plots demonstrated the augmentation of the corrosion current density with the number of accumulative roll bonding passes. EIS plots depicted that polarization resistance decreased by increasing the passes number of accumulative roll bonding process. Moreover, M-S analysis revealed that the donor density of the passive layers increased in a higher number of accumulative roll bonding passes.

Materials Science and Engineering: A, 2017

Grain-refining process in commercial pure titanium was performed by room-temperature accumulative... more Grain-refining process in commercial pure titanium was performed by room-temperature accumulative roll bonding. The study on the microstructural evaluations showed a reduction in grain size from about 45 µm in the untreated (annealed) sample to about 90 nm after six cycles of accumulative roll bonding, a reduction factor of about 500 times. The yield strength of the nano-grained commercially pure titanium after the sixth cycle, 799 MPa, was about three times higher than that of the as-received sample, 284 MPa. Different strengthening mechanisms during the accumulative roll bonding processing of the commercially pure Ti were assessed, and the contribution of each mechanism to the yield strength improvement was quantitatively calculated. The results showed that the calculated yield strength (834 MPa) for a six-cycle processed sample is close to the measured value (799 MPa).

Materials Science and Engineering: C, 2017

In the present study, various electrochemical tests were used to investigate the passive and elec... more In the present study, various electrochemical tests were used to investigate the passive and electrochemical response of annealed and nano-grained commercial pure Titanium in Ringer's physiological solution at 37°C. Nano-grained pure Titanium, which typically has an average grain size of 90 ± 5 nm, was obtained by sixcycle accumulative roll bonding process. Polarization and electrochemical impedance spectroscopy plots illustrated that as a result of grain refinement process, the passive response of the nano-grained sample was improved compared to that of its coarse-grained counterpart in Ringer's physiological solution. Mott-Schottky analysis indicated that the passive films behaved as n-type semiconductors in Ringer's physiological solution and grain refinement did not change the conductivity type of the passive films. Additionally, Mott-Schottky analysis showed that the donor density decreased by grain size reduction. Finally, nano-grained sample appeared to be more suitable for implant applications, mainly due to the formation of thicker and less defective oxide film.

Journal of Materials Engineering and Performance, 2016

Corrosion resistance improvement of plasma electrolyte oxidation coatings on 6061 aluminum alloy ... more Corrosion resistance improvement of plasma electrolyte oxidation coatings on 6061 aluminum alloy in silicate electrolyte containing Al 2 O 3 nano-particles was studied, with particular emphasis on the microstructure, coating growth, and corrosion behavior in 3.5 wt.% NaCl solution. The microstructure of coatings, their thickness, and phase composition were characterized using scanning electron microscopy and x-ray diffraction. All characterization data showed that the maximum coating thickness and lowest amount of porosity were obtained in a low concentration of KOH, a high concentration of Na 2 SiO 3 , and moderate concentration of Al 2 O 3 nano-particles in the electrolyte. This combination describes the optimum plasma electrolytic oxidation electrolyte, which has the best conductivity and oxidizing state, as well as the highest incorporation of electrolyte components in the coating growth process. On the other hand, incorporation and co-deposition of Al 2 O 3 nano-particles were more pronounced than SiO 3 22 ions in some level of molar concentration, which is due to the higher impact of electron discharge force on the adsorption of Al 2 O 3 nano-particles. The electrochemical results showed that the best protective behavior was obtained in the sample having a coat with the lowest porosity and highest thickness.

Journal of Materials Engineering and Performance, 2015

ABSTRACT

Journal of Alloys and Compounds, 2015

In this study, the effect of accumulative roll bonding (ARB) process on the electrochemical behav... more In this study, the effect of accumulative roll bonding (ARB) process on the electrochemical behavior of pure copper in 0.01 M borax solution has been investigated. The microhardness tests showed that by implementing the ARB process the values of microhardness improve with increasing the number of ARB cycles. Moreover, a drastic increase of microhardness was seen (~100%) after the second ARB cycle. Potentiodynamic polarization plots and electrochemical impedance spectroscopy (EIS) measurements showed that increasing the number of ARB cycles offer better conditions for forming the passive films. In the Mott-Schottky analysis, no evidence for n-type behavior was obtained, indicating that the oxygen vacancies and the copper interstitials do not have any significant population density in the passive films. Also, this analysis revealed that with increasing the number of ARB cycles, the acceptor density of the passive films decreased.

Journal of Manufacturing Processes, 2016

Abstract Effect of ARB process on mechanical and electrochemical properties of AA1050 was investi... more Abstract Effect of ARB process on mechanical and electrochemical properties of AA1050 was investigated. AFM images represented nano-scale roughness of ARBed samples which decreased with increasing the number of ARB cycles. TEM micrographs indicated that with increasing the cycle number of ARB process, the grain size of samples decreased and UFG structure achieved. Based on TEM images, final grain size after nine cycles of ARB reached to 270 nm. Results of tensile test showed that as the number of ARB cycles increased, the mechanical characterization of samples improved. Potentiodynamic polarization and EIS plots revealed the enhancement of passive behavior of samples with increasing the cycle number of ARB process. Also, semiconducting behavior of passive films was investigated by using the Mott–Schottky analysis. The outcomes revealed that passive films of all samples behaved as n-type semiconductor, and donor density decreased with increasing cycle number of ARB process. Compared to annealed sample, it was found that electrochemical behavior of the ARBed samples improved by increasing the processing cycle number, which is due to grain refinement.

Acta Metallurgica Sinica (English Letters), 2016

In this study, ceramic coatings were deposited on 6061 Al alloy using a plasma electrolytic oxida... more In this study, ceramic coatings were deposited on 6061 Al alloy using a plasma electrolytic oxidation (PEO) technique, and the effect of concentrations of KOH and Na 2 SiO 3 as electrolytes for PEO process was studied on microstructure, chemical composition, and electrochemical behavior of PEO coatings formed on the 6061 Al alloy. The results indicated that the increase in concentration of KOH led to rise in electrical conductivity of electrolyte. Consequently, the breakdown voltage reduced, which in turn improved the surface quality and the corrosion behavior. Moreover, the increase in concentration of Na 2 SiO 3 resulted in the increase in incorporation of Si in the coating, which led to a higher corrosion potential in the concentration of 4 g L-1. According to this investigation, the best protection behavior of coatings can be obtained when the KOH and Na 2 SiO 3 concentrations in PEO electrolyte are equal to 4 g L-1 .

Transactions of the Indian Institute of Metals, 2016

This study aims at investigating the effect of friction stir welding (FSW) on the electrochemical... more This study aims at investigating the effect of friction stir welding (FSW) on the electrochemical behavior of pure copper in 0.01 M borax solution (pH = 9.1). For this purpose, pure copper was welded with rotation speeds of 355 and 500 rpm and welding speeds of 20, 28 and 40 mm/min. Before any electrochemical measurements, evaluation of pure copper and welded pure copper microstructures was obtained by X-ray diffraction and scanning electron microscopy. Furthermore, the electrochemical behavior of the samples in 0.01 M borax solution was investigated by using open circuit potential measurements, potentiodynamic polarization tests, electrochemical impedance spectroscopy (EIS) and Mott–Schottky analysis. The results indicated that FSW led to reduction of the grain size of pure copper and improvement of resistance against the stir corrosion area. Also according to Mott–Schottky analysis, it was found that the calculated acceptor density decreased with decreasing the grain size of the stir zone. These results were consistent with the results of the potentiodynamic polarization and EIS measurements, evidencing that the electrochemical behavior of the stir zone enhanced with decreasing of the grain size.

Journal of Manufacturing Processes, 2015

In this study, the effect of Friction Stir Welding (FSW) on the corrosion behavior of 1050 alumin... more In this study, the effect of Friction Stir Welding (FSW) on the corrosion behavior of 1050 aluminium alloy in 3.5 wt.% NaCl solution was investigated.Is so doing, 1050 aluminium alloy was welded with the rotational speed of 250, 500 and 1000 rpm and traveling speeds of 14 and 56 mm per minute. The microstructure of 1050 aluminium al and welded 1050 aluminium alloy was examined by X-ray diffraction.Corrosion behavior of the samples was evaluated in 3.5 wt.% NaCl solution using Tafel polarization tests and electrochemical impedance spectroscopy. The results showed that Friction Stir Welding (FSW) decreases the grain size of 1050 aluminium al and improve the corrosion resistance of stir zone. X-ray diffraction pattern was similar for 1050 aluminium alloy and welded samples indicating the absence of unwanted phases in the structure. Given the curves of Tafel polarization and the results from modeling through electrical equivalent circuit expressed that for 1050 aluminium alloy welded by FSW with pin travelling speed equaled to 56 mm per minute with rotating speed equaled to 500 rpm, the most polarization resistance was obtained and it has also shown the least hardness in the hardness test compared to the other samples.

Journal of Materials Engineering and Performance, 2015

In this study, the effect of KOH concentration on the electrochemical properties of micro-arc oxi... more In this study, the effect of KOH concentration on the electrochemical properties of micro-arc oxidation (MAO) coated Mg alloy AZ31B has been investigated. Also, the surface morphology and chemical composition of the MAO coatings have been characterized by scanning electron microscopy and x-ray diffraction. In MAO process, an increase in the concentration of KOH as a result of increase in the electrolyte electrical conductivity leads to a reduction in sparking which in turn improves the quality and the behavior of anodic coatings in the concentration of 2.5 M. Moreover, it can be concluded that the MAO coating shows its best protective behavior when KOH concentration is equal 2.5 M, and if the concentration is higher or lower than this value, the protective properties of MAO coating will decrease.

international journal of iron and steel society of iran, 2013

This paper focused on the characterization of electrochemical behavior of a martensitic stainless... more This paper focused on the characterization of electrochemical behavior of a martensitic stainless steel in the acidic solutions. For this purpose, electrochemical parameters were derived from potentiodynamic polarization, Mott Schottky analysis and electrochemical impedance spectroscopy (EIS) techniques. The potentiodynamic polarization results showed that corrosion current density of AISI 420 stainless steel was decreased with the decrease in the concentration of solution. EIS studies also showed that as concentration was decreased, the measured value of polarization resistance was increased. This trend was due to the decrease in the corrosion current density, which corresponded to potentiodynamic polarization curves. Mott Schottky analysis revealed that passive films behaved as n-type and p-type semiconductors at potentials below and above the flat band potential, respectively. Also, Mott Schottky analysis indicated that the donor and acceptor densities were increased with solutio...

Applied Surface Science Advances, 2021

Magnesium is known as a suitable biological material because of its biocompatibility and biodegra... more Magnesium is known as a suitable biological material because of its biocompatibility and biodegradability. The most important limitation of magnesium and its alloys is their poor corrosion resistance. Having a standard electrochemical potential of-2.38 V, magnesium and its alloys are considered to be the most anodic structural metal compared to the standard hydrogen electrode. Poor corrosion performance of magnesium and its alloys has resulted in a reduction in their chemical stability as well as limited use in corrosive media. One solution to overcome this obstacle is surface modification of these alloys. A variety of coating methods have been studied to provide protection for magnesium and its alloys against corrosion, including PEO. An important parameter in this process is chemical composition of the electrolyte. Changing the condition of the electrolyte based on the presence of particles is one of the beneficial approaches to reduce the porosity of the coating and improve its final behaviors. Suitable properties of zirconia nanoparticle including great mechanical strength, good corrosion resistance in addition to antibacterial properties are the main reasons for its usage. This paper summarizes the findings of the researches on the utilization of zirconia nanoparticles in the PEO coating process of magnesium and its alloys which includes the effect of the nanoparticle on microstructure, corrosion, mechanical and tribological properties of the alloys.

Journal of Materials Research and Technology, 2021

Abstract The main aim of this study is to develop ZrN/CrN nanolayered coatings with bilayers peri... more Abstract The main aim of this study is to develop ZrN/CrN nanolayered coatings with bilayers periods 10 bilayers (10 L), 20 bilayers (20 L) and 30 bilayers (30 L) over AISI 304 stainless steel and also evaluating the effect of nanolayers architecture on their electrochemical behavior. The nanolayers were deposited from chromium and zirconium targets using the cathodic arc evaporation physical vapor deposition (Arc-PVD) technique in a nitrogen atmosphere. The nanolayer microstructure and morphology were evaluated using X-ray diffraction (XRD), atomic force microscopy (AFM), and field emission scanning electron microscopy (FE-SEM). The chemical composition was studied by energy-dispersive X-ray spectroscopy (EDS) tests. The electrochemical characterization was carried out by potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) tests in 3.5 wt. % NaCl solution in order to investigate changes in the electrochemical behavior as a function of the deposited bilayers number. The existence of CrN and ZrN phases with FCC lattices in the nanolayers were identified by the XRD patterns. The FE-SEM observations showed that the multilayered coatings were deposited at an excellent periodicity. The electrochemical tests indicated that the corrosion resistance of ZrN/CrN nanolayers is enhanced by increasing the number of bilayer periods that can be ascribed to the decrease in the pinholes and blocking the penetration path of corrosive solution.

Journal of Asian Ceramic Societies, 2020

The aim of this research is the evaluation of the influence of TiN, CrN and TiN/CrN nanostructure... more The aim of this research is the evaluation of the influence of TiN, CrN and TiN/CrN nanostructured coatings on corrosion resistance of nickel-chromium dental alloy in artificial saliva environment with two pH levels (3.0 and 6.5). Nickel-chromium alloy tested in this study were more resistant to corrosion in artificial saliva conditioning media when coated with different types of coating materials, as compared to uncoated alloy. The electrochemical measurements propose that the alloy with CrN coating has shown a high corrosion resistance in different pH levels. The superior passivation of CrN monolayer coating in modified Fusayama artificial saliva solution may be concluded from two essential factors, passive range, and corrosion current density. The passive range is well-developed, while the corrosion current density is much lower if compared to the other groups. Also, the Nyquist and polarization plots reveal that TiN, CrN and TiN/CrN nanostructured coatings have an excellent corrosion resistance which is considered much higher if compared to the substrate. The values of corrosion current density for CrN nanostructured coating in artificial saliva environment with two pH levels of 3.0 and 6.5 were 1.373 × 10 −8 and 5.416 × 10 −8 A.cm −2 , respectively that were the lowest corrosion current density values among the other samples.

Journal of Asian Ceramic Societies, 2020

Ceramics International, 2020

Corrosion Science, 2018

In the present work, the role of cold deformation and anodic potential on the electrochemical res... more In the present work, the role of cold deformation and anodic potential on the electrochemical response of pure nickel in borate buffer solutions were investigated. The application of cold deformation gave rise to a more localized microstructure that contained a greater number of fine grains. In order to investigation of the electrochemical response of specimens, potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), and Mott-Schottky (M-S) analysis were performed. As a result, with increasing of applied potential, the polarization resistance and passive film thickness decreased. Also, density of electron acceptor at passive layer decreased by increasing of applied potential.

Journal of Alloys and Compounds, 2018

Recently, high power impulse magnetron sputtering (HIPIMS) technique has been widely applied to d... more Recently, high power impulse magnetron sputtering (HIPIMS) technique has been widely applied to deposit hard coatings such as Ti-based coatings on industrial tools due to its strong merits of high coating density, smooth surface, and excellent adhesion. In this work, TiN (Titanium Nitride) nanostructured coatings were deposited by two different methods (HIPIMS and DCMS techniques) with constant processing parameters and their electrochemical behaviors were investigated in a 3.5% NaCl solution. X-ray diffraction (XRD), field emission scanning microscopy (FE-SEM), and atomic force microscopy (AFM) were used to characterize and evaluate the coatings composition, surface morphology, and surface roughness, respectively. It is found that the preferred orientation depends on the applied deposition technique. Potentiodynamic polarization measurements and electrochemical impedance spectroscopy (EIS) were used to compare the electrochemical responses of these nanostructured coatings in 3.5% NaCl solution. The results indicate that HIPIMS-TiN coating is of well-defined denser nanocrystalline structure, which not only is smoother but also has a superior passivation and better protects the substrate against the ingress of aggressive anions.

The International Journal of Advanced Manufacturing Technology, 2017

The microstructural evolution and mechanical properties of a new Al-3.8Cu-1.2Li-0.4 Mg-0.4Zn-0.4A... more The microstructural evolution and mechanical properties of a new Al-3.8Cu-1.2Li-0.4 Mg-0.4Zn-0.4Ag-0.3Mn-X alloy treated at different solution temperatures were investigated. The grain size was measured in optical micrograph (OM). The residual particles and the major precipitates were identified by electron probe microanalysis (EPMA), scanning electron microscopy (SEM) and transmission electron microscope (TEM), respectively. The results show that the peak strength appears at 530°C/1 h ? T6(165°C/20 h) and the values are 566.2 MPa (tensile strength) and 538.2 MPa (yield strength) with the elongation of 6.5 %. The strength of the alloy increases rapidly with the amount of the precipitates T 1 and h 0 increasing when the solution temperature is 530°C. The increase in density of precipitates is resulted from the residual particles Al 2 Cu, and particles enriched with Cu, Mg, Zr and Ag dissolve into matrix gradually with the solution temperature increasing. Finally, the number of precipitates decreases and part of the grain boundary weakens with a further increase in solution temperature from 540 to 550°C, leading to a decline of strength.

Journal of Alloys and Compounds, 2017

The present study investigated the influence of grain refinement on the passive and electrochemic... more The present study investigated the influence of grain refinement on the passive and electrochemical response of 2024 Al alloy in a borate buffer solution. Optical microscopy and transmission electron microscopy (TEM) micrograph depicted that with increasing the pass number of accumulative roll bonding process, the grain size of samples decreased and ultra-fine grained structure achieved. Also, the X-ray diffraction (XRD) analysis revealed that mean crystallite size decreased with increasing the number of accumulative roll bonding passes. To investigate the electrochemical behavior, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and Mott-Schottky (M-S) analysis was carried out. Potentiodynamic polarization plots demonstrated the augmentation of the corrosion current density with the number of accumulative roll bonding passes. EIS plots depicted that polarization resistance decreased by increasing the passes number of accumulative roll bonding process. Moreover, M-S analysis revealed that the donor density of the passive layers increased in a higher number of accumulative roll bonding passes.

Materials Science and Engineering: A, 2017

Grain-refining process in commercial pure titanium was performed by room-temperature accumulative... more Grain-refining process in commercial pure titanium was performed by room-temperature accumulative roll bonding. The study on the microstructural evaluations showed a reduction in grain size from about 45 µm in the untreated (annealed) sample to about 90 nm after six cycles of accumulative roll bonding, a reduction factor of about 500 times. The yield strength of the nano-grained commercially pure titanium after the sixth cycle, 799 MPa, was about three times higher than that of the as-received sample, 284 MPa. Different strengthening mechanisms during the accumulative roll bonding processing of the commercially pure Ti were assessed, and the contribution of each mechanism to the yield strength improvement was quantitatively calculated. The results showed that the calculated yield strength (834 MPa) for a six-cycle processed sample is close to the measured value (799 MPa).

Materials Science and Engineering: C, 2017

In the present study, various electrochemical tests were used to investigate the passive and elec... more In the present study, various electrochemical tests were used to investigate the passive and electrochemical response of annealed and nano-grained commercial pure Titanium in Ringer's physiological solution at 37°C. Nano-grained pure Titanium, which typically has an average grain size of 90 ± 5 nm, was obtained by sixcycle accumulative roll bonding process. Polarization and electrochemical impedance spectroscopy plots illustrated that as a result of grain refinement process, the passive response of the nano-grained sample was improved compared to that of its coarse-grained counterpart in Ringer's physiological solution. Mott-Schottky analysis indicated that the passive films behaved as n-type semiconductors in Ringer's physiological solution and grain refinement did not change the conductivity type of the passive films. Additionally, Mott-Schottky analysis showed that the donor density decreased by grain size reduction. Finally, nano-grained sample appeared to be more suitable for implant applications, mainly due to the formation of thicker and less defective oxide film.

Journal of Materials Engineering and Performance, 2016

Corrosion resistance improvement of plasma electrolyte oxidation coatings on 6061 aluminum alloy ... more Corrosion resistance improvement of plasma electrolyte oxidation coatings on 6061 aluminum alloy in silicate electrolyte containing Al 2 O 3 nano-particles was studied, with particular emphasis on the microstructure, coating growth, and corrosion behavior in 3.5 wt.% NaCl solution. The microstructure of coatings, their thickness, and phase composition were characterized using scanning electron microscopy and x-ray diffraction. All characterization data showed that the maximum coating thickness and lowest amount of porosity were obtained in a low concentration of KOH, a high concentration of Na 2 SiO 3 , and moderate concentration of Al 2 O 3 nano-particles in the electrolyte. This combination describes the optimum plasma electrolytic oxidation electrolyte, which has the best conductivity and oxidizing state, as well as the highest incorporation of electrolyte components in the coating growth process. On the other hand, incorporation and co-deposition of Al 2 O 3 nano-particles were more pronounced than SiO 3 22 ions in some level of molar concentration, which is due to the higher impact of electron discharge force on the adsorption of Al 2 O 3 nano-particles. The electrochemical results showed that the best protective behavior was obtained in the sample having a coat with the lowest porosity and highest thickness.

Journal of Materials Engineering and Performance, 2015

ABSTRACT

Journal of Alloys and Compounds, 2015

In this study, the effect of accumulative roll bonding (ARB) process on the electrochemical behav... more In this study, the effect of accumulative roll bonding (ARB) process on the electrochemical behavior of pure copper in 0.01 M borax solution has been investigated. The microhardness tests showed that by implementing the ARB process the values of microhardness improve with increasing the number of ARB cycles. Moreover, a drastic increase of microhardness was seen (~100%) after the second ARB cycle. Potentiodynamic polarization plots and electrochemical impedance spectroscopy (EIS) measurements showed that increasing the number of ARB cycles offer better conditions for forming the passive films. In the Mott-Schottky analysis, no evidence for n-type behavior was obtained, indicating that the oxygen vacancies and the copper interstitials do not have any significant population density in the passive films. Also, this analysis revealed that with increasing the number of ARB cycles, the acceptor density of the passive films decreased.

Journal of Manufacturing Processes, 2016

Abstract Effect of ARB process on mechanical and electrochemical properties of AA1050 was investi... more Abstract Effect of ARB process on mechanical and electrochemical properties of AA1050 was investigated. AFM images represented nano-scale roughness of ARBed samples which decreased with increasing the number of ARB cycles. TEM micrographs indicated that with increasing the cycle number of ARB process, the grain size of samples decreased and UFG structure achieved. Based on TEM images, final grain size after nine cycles of ARB reached to 270 nm. Results of tensile test showed that as the number of ARB cycles increased, the mechanical characterization of samples improved. Potentiodynamic polarization and EIS plots revealed the enhancement of passive behavior of samples with increasing the cycle number of ARB process. Also, semiconducting behavior of passive films was investigated by using the Mott–Schottky analysis. The outcomes revealed that passive films of all samples behaved as n-type semiconductor, and donor density decreased with increasing cycle number of ARB process. Compared to annealed sample, it was found that electrochemical behavior of the ARBed samples improved by increasing the processing cycle number, which is due to grain refinement.

Acta Metallurgica Sinica (English Letters), 2016

In this study, ceramic coatings were deposited on 6061 Al alloy using a plasma electrolytic oxida... more In this study, ceramic coatings were deposited on 6061 Al alloy using a plasma electrolytic oxidation (PEO) technique, and the effect of concentrations of KOH and Na 2 SiO 3 as electrolytes for PEO process was studied on microstructure, chemical composition, and electrochemical behavior of PEO coatings formed on the 6061 Al alloy. The results indicated that the increase in concentration of KOH led to rise in electrical conductivity of electrolyte. Consequently, the breakdown voltage reduced, which in turn improved the surface quality and the corrosion behavior. Moreover, the increase in concentration of Na 2 SiO 3 resulted in the increase in incorporation of Si in the coating, which led to a higher corrosion potential in the concentration of 4 g L-1. According to this investigation, the best protection behavior of coatings can be obtained when the KOH and Na 2 SiO 3 concentrations in PEO electrolyte are equal to 4 g L-1 .

Transactions of the Indian Institute of Metals, 2016

This study aims at investigating the effect of friction stir welding (FSW) on the electrochemical... more This study aims at investigating the effect of friction stir welding (FSW) on the electrochemical behavior of pure copper in 0.01 M borax solution (pH = 9.1). For this purpose, pure copper was welded with rotation speeds of 355 and 500 rpm and welding speeds of 20, 28 and 40 mm/min. Before any electrochemical measurements, evaluation of pure copper and welded pure copper microstructures was obtained by X-ray diffraction and scanning electron microscopy. Furthermore, the electrochemical behavior of the samples in 0.01 M borax solution was investigated by using open circuit potential measurements, potentiodynamic polarization tests, electrochemical impedance spectroscopy (EIS) and Mott–Schottky analysis. The results indicated that FSW led to reduction of the grain size of pure copper and improvement of resistance against the stir corrosion area. Also according to Mott–Schottky analysis, it was found that the calculated acceptor density decreased with decreasing the grain size of the stir zone. These results were consistent with the results of the potentiodynamic polarization and EIS measurements, evidencing that the electrochemical behavior of the stir zone enhanced with decreasing of the grain size.

Journal of Manufacturing Processes, 2015

In this study, the effect of Friction Stir Welding (FSW) on the corrosion behavior of 1050 alumin... more In this study, the effect of Friction Stir Welding (FSW) on the corrosion behavior of 1050 aluminium alloy in 3.5 wt.% NaCl solution was investigated.Is so doing, 1050 aluminium alloy was welded with the rotational speed of 250, 500 and 1000 rpm and traveling speeds of 14 and 56 mm per minute. The microstructure of 1050 aluminium al and welded 1050 aluminium alloy was examined by X-ray diffraction.Corrosion behavior of the samples was evaluated in 3.5 wt.% NaCl solution using Tafel polarization tests and electrochemical impedance spectroscopy. The results showed that Friction Stir Welding (FSW) decreases the grain size of 1050 aluminium al and improve the corrosion resistance of stir zone. X-ray diffraction pattern was similar for 1050 aluminium alloy and welded samples indicating the absence of unwanted phases in the structure. Given the curves of Tafel polarization and the results from modeling through electrical equivalent circuit expressed that for 1050 aluminium alloy welded by FSW with pin travelling speed equaled to 56 mm per minute with rotating speed equaled to 500 rpm, the most polarization resistance was obtained and it has also shown the least hardness in the hardness test compared to the other samples.

Journal of Materials Engineering and Performance, 2015

In this study, the effect of KOH concentration on the electrochemical properties of micro-arc oxi... more In this study, the effect of KOH concentration on the electrochemical properties of micro-arc oxidation (MAO) coated Mg alloy AZ31B has been investigated. Also, the surface morphology and chemical composition of the MAO coatings have been characterized by scanning electron microscopy and x-ray diffraction. In MAO process, an increase in the concentration of KOH as a result of increase in the electrolyte electrical conductivity leads to a reduction in sparking which in turn improves the quality and the behavior of anodic coatings in the concentration of 2.5 M. Moreover, it can be concluded that the MAO coating shows its best protective behavior when KOH concentration is equal 2.5 M, and if the concentration is higher or lower than this value, the protective properties of MAO coating will decrease.