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Materials science and Engineering - Volume:13 Issue: 2, Jun 2016

Iranian Journal of Materials science and Engineering
Volume:13 Issue: 2, Jun 2016

  • تاریخ انتشار: 1395/05/02
  • تعداد عناوین: 9
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  • E. Eshghi, M. Kadkhodayan Pages 1-9
    High speed and absence of a precise control over pressure distribution confine sheet Electromagnetic Forming into a die to simple shapes having shallow depth. It is possible to reach a higher depth by using a convex punch instead of a concave die. In this study, sheet Electromagnetic Forming on a punch and sheet Electromagnetic Forming into a die are investigated. The electromagnetic part of the study is investigated analytically and its mechanical part is studied numerically. In order to couple electromagnetic with mechanical parts, no-coupling method is used. The obtained results are verified by comparing the obtained results with previous experimental ones in literature. Rate-dependent and rate-independent hardenings are taken into consideration for the mechanical behavior for material of AAl1050. Using appropriate hardening model for material yields acceptable results. Moreover, a convex punch instead of a concave die is used to reach to a higher depth in sheet Electromagnetic Forming.
    Keywords: High speed forming, Electromagnetic forming, Convex punch, FEM, Strain rate
  • Z. Sadeghian, R. Dezfulizadeh Pages 10-19
    In situ Al2024- Mg2Si composite was fabricated by spark plasma sintering (SPS) of reactive powder. Reactive powder was obtained from mechanical alloying (MA) of elemental powders. Clad layers of in situ composite were fabricated on Al substrates by spark plasma sintering (SPS). Structural evolution during MA process and after SPS was investigated by X-ray diffractometery (XRD). Scanning electron microscopy (SEM) was utilized to study the microstructure of sintered samples. Hardness and tensile behavior of sintered samples were investigated. The results showed that SPS of mechanically alloyed unreacted powder can result in the in situ formation of Mg2Si and Mg2Al3 within the Al matrix. SPSed clad layer showed a sound and clear interface to the Al substrate with a hardness of about 140 HV. Sintered in situ composite exhibited a tensile strength of 288 MPa.
    Keywords: Al composite, Mg2Si, Mechanical alloying, Spark plasma sintering
  • A. A. Babakoohi Ashrafi, H. Mohammadi, A. Habibolla Zade Pages 20-28
    In this paper, the influence of heat treatment on PH17-7 stainless steel spring was evaluated. Precipitation hardening phenomenon of PH 17-7 steel was evaluated in three stages. First, the spring constant changes with time and temperature was evaluated. Second, the spring constant changes with respect to its original length at constant temperature and time with blocking (spring length after compression, 18 and 21 mm) were investigated. And finally, the spring heat treatment at 480 °C for 80 min and then holding at 230 °C in oil bath for 60 min without blocking were investigated. The results showed that the use of 18 mm block have large spring constant than 21 mm block. The optimal conditions (480°C for 80 min) for this spring to reaching maximum spring constant were determined.
    Keywords: PH 17, 7 stainless steel, precipitation hardening, spring constant, blocking
  • H. Adelkhani, Kh. Didehban, R. Dehghan Pages 29-34
    In this study, polyaniline-graphene composites with different nano-structures are synthesized and the behaviour of the obtained composites serving as electrode materials in electrochemical capacitors is studied. The morphology, crystal structure, and thermal stability of the composites are examined using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Thermal gravimetric analysis (TGA). Electrochemical properties are characterized by cyclic voltammetry (CV). According to the results, the obtained composites show different crystal structures and different thermal stabilities, and consequently different electrochemical capacities, when used as electrodes in electrochemical capacitors. A nano-fibre composite is shown to have a good degree of crystallization, 5.17% water content, 637oC degradation onset temperature, and 379 Fg-1 electrochemical capacity.
    Keywords: Polyaniline, graphene, Composite materials, Electrochemical capacitors, Nano, structure, Thermal properties
  • A. Shabani, M. R. Toroghinejad, A. Shafyei Pages 35-43
    In the present study, the effect of post-rolling annealing heat treatment on the formation of intermetallic compounds between Al-Cu strips, in the presence of nickel coating on the Cu strips, was investigated. In addition, the effect of post-rolling annealing and intermetallic compounds on the bond strength of Al-Cu strips was evaluated. In order to prepare samples, Cu strips were coated with nickel by electroplating process. After surface preparing, Cu strips were placed between two Al strips and roll bonded. This method is used for producing Al-Ni-Cu composites. Then the samples were annealed at 773K for 2 h. The formation of intermetallic compounds was studied using energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). Also, in order to investigate bond strength of Al-Cu after post-rolling annealing heat treatment, samples were produced using nickel powder and nickel coating. Then bond strength of strips was investigated using peeling test. The results revealed that by post-rolling annealing of layers, the bond strength between Al-Cu strips decreases dramatically.
    Keywords: Intermetallic compounds, XRD, Bond strength, CRB process
  • S. Yazdani, S. Javadpour, Sh. Mehdizadeh Naderi, M. Javidi Pages 44-49
    The inherent reactivity of the Al–Cu alloys is such that their use for structural, marine, and aerospace components and structures would not be possible without prior application of a corrosion resistance system. Historically these corrosion resistance coatings were based on the use of chemicals containing Cr (VI) compounds. Silane coatings are of increasing interest in industry due to their potential application for the replacement of current toxic hexavalent chromate based treatments. In this study, hydrophobic coating sol was prepared with methyltriethoxysilane (MTES), methanol (MeOH), and water (as 7M NH4OH) at a molar ratio of 1:25:4.31 respectively. The coatings were applied by a dip-technique to 2024-T3 Al alloy, and subsequently cured at room temperature and there after heat treated in an oven at 150°C. The anticorrosion properties of the coatings within 3.5 wt% NaCl solution were studied by Tafel polarization technique. The sol–gel coating exhibited good anticorrosion properties providing an adherent protection film on the Al 2024-T3 substrate. The surface properties were characterized by water contact angle measurement, scanning electron microscopy (SEM), and the composition was studied by Fourier transform infrared spectroscopy (FTIR).
    Keywords: sol, gel, Al–Cu alloys, hydrophobic, anticorrosion
  • H. R. Sobhani Kavkani, A. Mortezaei, R. Naghizadeh Pages 50-61
    Different mineral admixtures of Indian metakaolin, Iranian silica fume and nanosilica were used to produce high performance mortars. Two different sands types with grain size of 0.015-4mm were mixed with type II Portland cement, polycarboxylate superplasticizer,mineral admixture with 650kg/m3 cement content and water/cement ratio of 0.35. Different amount of cement was replaced by metakaolin or silica fume (5-15wt%) or nanosilica (0.8-5wt%). After mixing, moulding and curing, compressive strength, electrical resistivity and abrasion resistance were studied. The maximum compressive strength of 28 days samples were 76MPa, 79MPa and 75MPa for 15wt% substitution of cement with metakaolin, silica fume and 5wt% with nanosilica. The compressive strength of these samples showed 28%, 33% and 26% increment in comparison with reference sample, respectively. X-ray patterns showed that replacing silica fume leads to reduction of Portlandite (Ca(OH)2) phase. This can be attributed to the pozzolanic reaction and formation of new hydrated calcium silicate phase (CSH) that caused improvement of strength of admixtures containing samples. The microstructure of silica fume containing sample also showed better bond between sand and matrix. The electrical resistivity of samples with 15wt% metakaolin or silica fume and 5wt% nanosilica reach to 21kΩ.cm, 15 kΩ.cm and 10kΩ.cm, respectively. These samples showed high durability and corrosion resistance relative to reference samples (3.4 kΩ.cm). The abrasion resistance of different admixtures, specially silica fume containing samples were improved.
    Keywords: Metakaolin, microsilica, nanosilica, cement mortar
  • M.H. Avazkonandeh, Gharavo, M.Haddad, Sabzevar, H. Fredriksson Pages 62-72
    Because the partition coefficient is one of the most important parameters affecting microsegregation, the aim of this research is to experimentally analyse the partition coefficient in Al-Mg alloys. In order to experimentally measure the partition coefficient, a series of quenching experiments during solidification were carried out. For this purpose binary Al-Mg alloys containing 6.7 and 10.2 wt-% Mg were melted and solidified in a DTA furnace capable of quenching samples during solidification. Cooling rates of 0.5 and 5 K/min were used and samples were quenched from predetermined temperatures during solidification. The fractions and compositions of the phases were measured by quantitative metallography and SEM/EDX analyses, respectively. These results were used to measure the experimental partition coefficients. The resultant partition coefficients were used to model the concentration profile in the primary phase and the results were compared with equilibrium calculations and experimental profiles. The results of calculations based on the experimental partition coefficients show better consistency with experimental concentration profiles than the equilibrium calculations.
    Keywords: Partition Coefficient, Microsegregation, Al, Mg Alloys, Differential Thermal Analysis
  • A. Azizi, S.Z. Shafaei, R. Rooki Pages 73-84
    Nowadays steel balls wear is a major problem in mineral processing industries and forms a significant part of the grinding cost. Different factors are effective on balls wear. It is needed to find models which are capable to estimate wear rate from these factors. In this paper a back propagation neural network (BPNN) and multiple linear regression (MLR) method have been used to predict wear rate of steel balls using some significant parameters including, pH, solid content, throughout of grinding circuit, speed of mill, charge weight of balls and grinding time. The comparison between the predicted wear rates and the measured data resulted in the correlation coefficients (R), 0.977 and 0.955 for training and test data using BPNN model. However, the R values were 0.936 and 0.969 for training and test data by MLR method. In addition, the average absolute percent relative error (AAPE) obtained 2.79 and 4.18 for train and test data in BPNN model, respectively. Finally, Analysis of the predictions shows that the BPNN and MLR methods could be used with good engineering accuracy to directly predict the wear rate of steel balls.
    Keywords: Wear rate, Steel balls, Grinding, Neural Network, Multiple Linear Regression