University of TehranJournal of Ultrafine Grained and Nanostructured Materials2423-684550120170601Accumulative Roll Bonding of Aluminum/Stainless Steel Sheets156208510.7508/jufgnsm.2017.01.01ENNavidMohammad Nejad FardSchool of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, P.O.Box 11155-4563, Tehran, Iran.HamedMirzadehSchool of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, P.O.Box 11155-4563, Tehran, Iran.0000-0001-7179-0052RezayatMohammadSchool of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, P.O.Box 11155-4563, Tehran, Iran.Jose-MariaCabreraDepartment of Materials Science and Metallurgical Engineering, Universidad Plitecnica de Catalunya, EEBE-c/Eduard Maristany 10-14, 08019 Barcelona, Spain.Journal Article20161208An Al/Stainless Steel/Al lamellar composite was produced by roll bonding of the starting sheets at 400 °C. Afterward, the roll bonded sheet was cut in half and the accumulative roll bonding (ARB) process at room temperature was applied seven times. As a result, the central steel layer fractured and distributed in the Al matrix among different layers introduced by the repetition of roll bonding process. The tensile results showed that the roll bonded sheet has much higher strength and strength to weight ratio compared with the initial aluminum sheet as a result of the presence of continuous steel core. However, poor ductility properties were observed during tensile test, which were ascribed to the increasing deformation resistance and localized thinning of the central stainless steel sheet during the roll bonding process. The ARBed sample exhibited lower strength compared with the roll bonded sheet due to the breakup of stainless steel layer into many small segments. Anyway, an ultrafine grained microstructure with average grain size of 400 nm in the aluminum matrix and 71% strain-induced martensite in the steel segments were detected by the electron backscattered diffraction (EBSD) technique, which were found to be responsible for the enhancement of mechanical properties compared with the initial aluminum sheet.University of TehranJournal of Ultrafine Grained and Nanostructured Materials2423-684550120170601Mechanical Behavior of an Ultrafine/Nano Grained Magnesium Alloy6156208610.7508/jufgnsm.2017.01.02ENSeyed MahmoodFatemiSchool of Mechanical Engineering, Shahid Rajaee Teacher Training University, 136-16785, Tehran, Iran.AbbasZarei-HanzakiDepartment of Metallurgical & Materials Engineering, University of Tehran, 515-14395, Tehran, Iran.Journal Article20170520The application of magnesium alloys is greatly limited because of their relatively low strength and ductility. An effective way to improve the mechanical properties of magnesium alloy is to refine the grains. As the race for better materials performance is never ending, attempts to develop viable techniques for microstructure refinement continue. Further refining of grain size requires, however, application of extreme value of plastic deformation on material. In this work, an AZ31 wrought magnesium alloy was processed by employing multipass accumulative back extrusion process. The obtained microstructure, texture, and room temperature compressive properties were characterized and discussed. The results indicated that grains of 80 nm to 1 μm size were formed during accumulative back extrusion, where the mean grain size of the experimental material was reduced by applying successive ABE passes. The fraction of DRX increased and the mean grain size of the ABEed alloy markedly lowered, as subsequent passes were applied. This helped to explain the higher yield stress govern the occurrence of twinning during compressive loading. Compressive yield and maximum compressive strengths were measured to increase by applying successive extrusion passes, while the strain-to-fracture dropped. The evolution of mechanical properties was explained relying on the grain refinement effect as well as texture change.University of TehranJournal of Ultrafine Grained and Nanostructured Materials2423-684550120170601Microstructure and mechanical properties of AZ91 tubes fabricated by Multi-pass Parallel Tubular Channel Angular Pressing16226208710.7508/jufgnsm.2017.01.03ENHoomanAbdolvandSchool of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, 11155-4563, Iran.GhaderFarajiSchool of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, 11155-4563, Iran.JavadShahbazi KaramiFaculty of Mechanical Engineering, Shahid Rajaee Teacher Training University, Tehran, Iran.Journal Article20161219Parallel Tubular Channel Angular Pressing (PTCAP) process is a novel recently developed severe plastic deformation (SPD) method for producing ultrafine grained (UFG) and nanograined (NG) tubular specimens with excellent mechanical and physical properties. This process has several advantageous compared to its TCAP counterparts. In this paper, a fine grained AZ91 tube was fabricated via multi pass parallel tubular channel angular pressing (PTCAP) process. Tubes were processed up to three passes PTCAP at 300 °C. Evolution of microstructure, mechanical properties and fracture behavior of the processed tubes after different passes were evaluated. Hardness, strength, and elongation were increased for processed tubes. Mean grain size was notably reduced to 3.8 μm for the tube which processed three passes from a 150 μm for the unprocessed tube. The maximum strength was found for second passes PTCAP processed tube which increased considerably about 108 %. The strength of the first pass processed tube increased about 62.5%. Increasing in elongation at room temperature was occurred, too. Mechanical properties of the third pass processed tube were deteriorated relatively because of appearing microcracks on the surface. Also, the hardness improved and it was increased about 77%. The result showed that the achieved mechanical properties consistent with microstructure.University of TehranJournal of Ultrafine Grained and Nanostructured Materials2423-684550120170601Hardness Optimization for Al6061-MWCNT Nanocomposite Prepared by Mechanical Alloying Using Artificial Neural Networks and Genetic Algorithm23326208810.7508/jufgnsm.2017.01.04ENMehrdadMahdavi JafariDepartment of Materials Science and Engineering, Shahid Bahonar University of Kerman, Kerman, Iran.SoheilSoroushianDepartment of Materials Science and Engineering, Shahid Bahonar University of Kerman, Kerman, Iran.Gholam RezaKhayatiDepartment of Materials Science and Engineering, Shahid Bahonar University of Kerman, Kerman, Iran.Journal Article20161026Among artificial intelligence approaches, artificial neural networks (ANNs) and genetic algorithm (GA) are widely applied for modification of materials property in engineering science in large scale modeling. In this work artificial neural network (ANN) and genetic algorithm (GA) were applied to find the optimal conditions for achieving the maximum hardness of Al6061 reinforced by multiwall carbon nanotubes (MWCNTs) through modeling of nanocomposite characteristics. After examination the different ANN architectures an optimal structure of the model, i.e. 6-18-1, is obtained with 1.52% mean absolute error and R2 = 0.987. The proposed structure was used as fitting function for genetic algorithm. The results of GA simulation predicted that the combination sintering temperature 346 °C, sintering time 0.33 h, compact pressure 284.82 MPa, milling time 19.66 h and vial speed 310.5 rpm give the optimum hardness, (i.e., 87.5 micro Vickers) in the composite with 0.53 wt% CNT. Also, sensitivity analysis shows that the sintering time, milling time, compact pressure, vial speed and amount of MWCNT are the significant parameter and sintering time is the most important parameter. Comparison of the predicted values with the experimental data revealed that the GA–ANN model is a powerful method to find the optimal conditions for preparing of Al6061-MWCNT.University of TehranJournal of Ultrafine Grained and Nanostructured Materials2423-684550120170601Corrosion Inhibition of Sodium Phosphate for Coarse and Near Ultrafined-Grain Mild steel surface33426208910.7508/jufgnsm.2017.01.05ENKazemSabet BokatiSchool of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran, Iran.ChangizDehghanianSchool of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran, Iran.Journal Article20170312An ultrafine grain surface layer with average crystallite size of 28 nm was produced on annealed mild steel through a wire brushing process. The effects of grain size reduction on the inhibition performance of sodium phosphate were investigated using polarization and electrochemical impedance spectroscopy (EIS) measurements. The crystal grain size of wire brushed surface was analyzed by X-ray diffractometry (XRD) and field emission scanning electron microscopy (FESEM). The electrochemical tests were conducted in artificial sea water (ASW) in the presence and absence of 250 mg/lit sodium phosphate (SP). The wire brushed surface indicated considerable deformed plastic flows and high surface roughness. Due to the accumulated strains, a deformed layer with thickness of 20±5 μm was produced and the crystal grain size of severe deformed zone was about 28 nm. Wire brushed surface increased uniform corrosion rate of mild steel due to enhanced surface roughness and preferential sites to adsorption of corrosive ions. However, the wire brushed surface showed a positive effect on inhibition performance of sodium phosphate. The electrochemical results revealed that average inhibition efficiency increased from 65 to about 80 percent in ASW solution containing 1.5 mM Na<sub>3</sub>PO<sub>4</sub> for coarse grained samples in comparison to that of ultra-fined grain samples respectively .The wire brushing process encouraged passivity on the surface in SP-containing solution due to a high density of nucleation sites which increased the adsorption of phosphate ions leading to a high fraction of passive layers and low corrosion rates.University of TehranJournal of Ultrafine Grained and Nanostructured Materials2423-684550120170601Photocatalytic Decolorization of Methyl Orange by Silica-Supported TiO2 Composites43506209010.7508/jufgnsm.2017.01.06ENMohammadGhorbanpourChemical Engineering Department, University of Mohaghegh Ardabili, P.O. Box 56199-11367, Ardabil, Iran.MehranYousofiChemical Engineering Department, University of Mohaghegh Ardabili, P.O. Box 56199-11367, Ardabil, Iran.SamanehLotfimanChemical Engineering Department, University of Mohaghegh Ardabili, P.O. Box 56199-11367, Ardabil, Iran.Journal Article20170116Immobilization of TiO<sub>2</sub> on silica gel has been proposed to enable easy separation of the catalyst in aqueous systems after photocatalytic reaction. Our simple synthesizing method reduces production cost, and the photocatalyst could find economical application in wastewater treatment. Silica-supported TiO<sub>2</sub> composites were prepared by molten salt method at 500, 600 and 700 °C for 60 min. The obtained samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), diffuse reflectance spectroscopy and X-ray fluorescence. SEM results showed a heterogeneous surface covered with spherical particles. According to XRD findings, the only phase of the prepared TiO<sub>2</sub>/SG nanocomposites at all temperatures was pure anatase. The average crystallite size of anatase was roughly 25, 42, 44 and 53 nm for nanocomposites prepared at 550, 600, 700 and 800 °C, respectively. The samples taken at 500 and 600 ºC showed a band gap value of 2.98 eV, and for sample synthesized at 700 ºC the band gap was 2.95 eV. The decolorization activity has been evaluated by Methyl orange (MO) oxidation in liquid phase. The results showed that the sample obtained at 700 °C had the highest photocatalytic decolorization efficiency activity, and the sample prepared at 500 °C had the lowest. The decolorization activity of photocatalyst prepared at 700 °C did not change during stability experiment.University of TehranJournal of Ultrafine Grained and Nanostructured Materials2423-684550120170601Mechanochemical Synthesis of Nanostructured MgXNi1-XO Compound by Mg-NiO Mixture51596209110.7508/jufgnsm.2017.01.07ENNaderSetoudehMaterials Engineering Department, Yasouj University, Yasouj, 75918-74831, Iran.CyrusZamaniSchool of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran, Iran.MohammadSajjadnejadMaterials Engineering Department, Yasouj University, Yasouj, 75918-74831, Iran.Journal Article20170215Synthesis of magnesium nickel oxide phase such as Mg<sub>x</sub>Ni<sub>1-x</sub>O solid solutions has been studied in this research article using mechnochmical reaction between magnesium and nickel oxide. Mixtures of magnesium powder and nickel oxide (Mg+NiO) with stoichiometric compositions were milled for different times in a planetary ball mill. Reduction reaction of nickel oxide by magnesium via a mechanically induced self-sustaining reaction (MSR) was confirmed in the XRD measurements of the as-milled samples. Formation of nanostructured magnesium nickel oxide phases (such as Mg<sub>0.4</sub>Ni<sub>0.6</sub>O or MgNiO<sub>2</sub>) was observed after isothermal heating of the 30 minutes milled samples at 1000°C where nickel phase seems to disappear in XRD patterns. The traces of phases such as Mg<sub>0.4</sub>Ni<sub>0.6</sub>O or MgNiO<sub>2</sub> were also observed in the as-milled mixtures. Therefore, the XRD results of the as-milled samples suggested that the formation of magnesium nickel oxide phases could be possible even after prolonged milling. The XRD and SEM results of both as-milled and isothermally heated samples indicated that the crystallite size and particle size of the final products reached to nanoscale after milling. Morphological and compositional evolution of the samples after heat treatment was monitored through SEM imaging and elemental analyses. The results confirmed that the composition of final product is close to Mg<sub>0.4</sub>Ni<sub>0.6</sub>O compound.University of TehranJournal of Ultrafine Grained and Nanostructured Materials2423-684550120170601Multiscale Evaluation of the Nonlinear Elastic Properties of Carbon Nanotubes Under Finite Deformation60806209210.7508/jufgnsm.2017.01.08ENAbolfazlShahabodiniDepartment of Mechanical Engineering, University of Guilan, P.O. Box 3756, Rasht, Iran.RezaAnsariDepartment of Mechanical Engineering, University of Guilan, P.O. Box 3756, Rasht, Iran.MansourDarvizehDepartment of Mechanical Engineering, University of Guilan, P.O. Box 3756, Rasht, Iran.Journal Article20170228This paper deals with the calculation of the elastic properties for single-walled carbon nanotubes (SWCNTs) under axial deformation and hydrostatic pressure using the atomistic-based continuum approach and the deformation mapping technique. A hyperelastic model based on the higher-order Cauchy-Born (HCB) rule being applicable at finite strains and accounting for the chirality and material nonlinearity is presented. Mechanical properties of several carbon nanotubes (CNTs) are computed and compared with the existing theoretical results and a good agreement is observed. Moreover, by comparison with atomistic calculations, it is found that the present model can reproduce the energetics of axially deformed CNTs. The model is then adopted to study the dependence of the elastic properties on chirality, radius and strain which yields an upper bound on the stability limit of axially and circumferentially stretched nanotubes. The influence of chirality is found to be more prominent for smaller tubes and as the diameter increases, the anisotropy induced by finite deformations gets nullified. It is discerned that the constitutive properties of the CNT can vary with deformation in a nonlinear manner. It is also found that the CNT displays a martial softening behavior at finite tensile strains and a hardening behavior at slightly compressive strains.