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Advanced Materials and Processing - Volume:5 Issue: 1, winter 2017

Journal of advanced materials and processing
Volume:5 Issue: 1, winter 2017

  • تاریخ انتشار: 1396/02/18
  • تعداد عناوین: 8
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  • Mohammad Jula, Reza Dehmolaei, Seyed Reza Alavi Zaree Pages 3-12
    In this study, an attempt was made to minimize the corrosion rate and maximize pitting potential of dissimilar metal welded joints of A387-Gr91/AISI316 steels. Process parameters of the pulsed current gas tungsten arc welding (PCGTAW) including of peak current (P), background current (B), pulse frequency (F), and on time percentage (O) were chosen as the influencing factors on corrosion behavior. Design of Experiments (DOE) were done using Taguchi’s L9 (34) orthogonal array. Signal to noise (S/N) ratio Analysis indicated that corrosion rate was affected by peak current, frequency, on time percentage, and background current whereas pitting potential was mostly influenced by on time percentage, peak current, frequency, and background current, respectively. Optimum conditions of P, B, F, and O factors were found as 135A, 75A, 10Hz, 80% for Corrosion rate and 120A, 60A, 6Hz, 60% for pitting potential, respectively. Furthermore, analysis of variance (ANOVA) demonstrated that the contribution of P, B, F, and O were 28.79%, 13.06%, 28.63%, and 29.51% for corrosion rate and 13.97%, 2.79%, 12.20%, and 71.04% for pitting potential, respectively. Results from welded samples at optimum conditions, showed good agreement with predicted values for corrosion rate and pitting potential.
    Keywords: Taguchi method, Analysis of variance (ANOVA), Pulsed current gas tungsten arc welding (PCGTAW), A387-Gr.91, AISI316
  • Maryam Shojaie Bahaabad Pages 13-21
    Boron carbide is one of the hardest materials. The combustion method was used to synthesize B4C-TiB2 nanocomposite powder in a B2O3-Mg-TiO2-C system. An experimental study of the formation of B4C–TiB2 nanoparticles was conducted in the thermal explosion mode. A mixture of B2O3:TiO2:Mg:C at a molecular ratio of 3:1:12:1 was chosen to obtain the B4C–TiB2. This powder mixture was milled for different times. The combustion reaction of powders milled for up to 12 h was done in an inert atmosphere at 900°C. The synthesized powders were characterized by X-Ray diffraction, Scanning and Transmission Electeron Microscopies (SEM and TEM). It was demonstrated that mechanical activation is a useful method for obtaining B4C and TiB2 powders simultaneously; without milling, the B4C composition did not form. B4C formed after 3 h of milling of the reactants. Crystallite size of products obtained from reactant powders milled for 6 and 12 hour was less than 100 nanometer.
    Keywords: Combustion synthesis, Milling, Boron carbide, Titanium diboride, Nanocomposite
  • Reza Ranjbar, Malek Naderi, Arash Ghazitabar Pages 22-31
    However, the conventional gold recovery process is cyanidation, due to the recent environmental laws; researchers are looking for alternative methods for the recovery of gold. Furthermore, the copper anode slime is one of the most important secondary sources of gold (about 1200 ppm). So, the main objective of the current work is gold separation from copper anode slime as a rich secondary source of gold by determining the mechanism of the reaction between thiourea (TU) and Hydrogen peroxide (H2O2) in the thiourea leaching of gold. Thiourea can form cationic complex with gold in gold extraction process from copper anode slime. Thiourea consumption levels were also examined during the leaching operations for different leaching parameters, i.e. solution volume, concentration ratio of thiourea/H2O2, pH, leaching time and Agitation rate. Ammonia was added to the gold containing solution, and consequently, gold was precipitated in the metallic form. X-Ray pattern confirms formation of metallic gold.
    Keywords: Recovery of gold, Thiourea, Copper anode slime
  • Javad Moradgholi, Amad Monshi, Khosro Farmanesh Pages 32-43
    In this work, the strength of cold roll bond of the commercially pure titanium (CP Ti) sheet and the effect of TiO2 nanoparticles on bond strength was investigated. Through the accumulative roll bonding process, which is considered among the important severe plastic deformation processes, the creation of suitable bonds plays a significance role in the ultimate strength of the bond. Thus, researchers first study the optimum bonding parameters of two or several metals producible via ARB method and, then, manufacture it. In the present work, the bond strength of the commercially pure titanium sheets was investigated and found that by applying a 50% thickness reduction a desirable bond strength is achieved based on the results of the peeling test for CP Ti. To study the effect TiO2 nanoparticles on nanocomposite preparation in ARB test, these nanoparticles were dispersed between the CP Ti sheets at 0.1, 0.3, and 0.5wt% concentrations; the results show a decrease in bond strength during the peeling test by the increase in TiO2 content. The scanning electron microscopy tests of the peeled sites revealed that the presence of cumulative layers of nanoparticles prevents bonding in these areas. Although the addition of TiO2 nanoparticles results in the reduced bond strength, at TiO2 percentages, equal or less than 0.5wt.% this decrease is negligible. Hence, ARB method can be considered as an efficient technique for preparation of bulk composite at room temperature.
    Keywords: CP Ti, cold roll, TiO2 nanoparticles, bond strength
  • Mehdi Safari, Hossein Mostaan Pages 44-56
    In this paper, dissimilar resistance spot welding of AISI 1075 eutectoid steel to AISI 201 stainless steel is investigated experimentally. For this purpose, the experiments are designed using response surface methodology and based on four-factor, five-level central composite design. The effects of process parameters such as welding current, welding time, cooling time and electrode force are investigated on the tensile-shear strength of resistance spot welds. The results show that tensile-shear strength of spot welds is increased with increase in the welding current and welding time. Also, it is concluded from results that with increasing the electrode force and cooling time, tensile-shear strength of welded joints is decreased. During tensile-shear tests, three failure modes are observed, namely interfacial, partial pullout and pullout modes. The analysis of variance for the tensile-shear strength indicates that the main effects of welding current, electrode force, welding time, cooling time, second- order effect of the welding current and cooling time, two level interactions of welding current with welding time, welding current with cooling time and electrode force with cooling time are significant model terms. The results of analysis of variance show that the presented model for tensile-shear strength of dissimilar resistance spot welds of AISI 1075 eutectoid steel to AISI 201 stainless steel can predict 95.00% of the experimental data and leave only 5.00% of the total variations as unexplained.
    Keywords: Dissimilar resistance spot welding, AISI 1075 eutectoid steel, AISI 201 stainless steel, Response surface methodology, Tensile-shear strength
  • Oladayo Olaniran Pages 57-68
    This work investigated the electrochemical and aqueous tribological behavior of hot pressed 2205 duplex stainless steel (DSS). DSS sintered composites of different volume percent (% vol) of partially stabilized zirconia (PSZ) was developed using powder metallurgy (PM) technique. Electrochemical behaviour was studied at room temperature, using open circuit potential and potentiodynamic scanning in simulated mine water and 3.5% NaCl solution while aqueous tribological test was carried out in simulated mine water. The influence of PSZ, Cr and Ni additions on the degradation mechanisms of corrosion and wear of the modified DSS were evaluated. X-Ray Microtomography (XRM) was used as experimental technique for defect analysis from the corrosion studies. Results show the surface imaging capability of SEM and the internal structures imaging capability of XRM. SEM revealed important surface degradation mechanisms of the materials whilst relevant information on pitting corrosion was obtained from XRM. It was deduced that, pitting corrosion can be caused by the growth of intergranular corrosion resulting from the attack and the breakdown of passive films by chloride ions which affected both the surface and the internal parts of the samples.
    Keywords: Key words: Electrochemical, Tribological, Oxide dispersion, Duplex stainless steel, X-ray microscopy
  • Mohammad Hassan Dadkhah Tehrani, Abdolreza Jafari Tadi, Yaghoub Yaghoubi Askarabad, Majid Karimian, Kamran Amini, Mohammad Hossein Dadkhah Tehrani Pages 69-80
    In the present work, structural characteristics and tribological properties of the Ti-Al-Cr-(Si)-C-N nanocomposite films coated on the SPK 1.2080 tool steel byPVD technique have been investigated. The PVD coating process was carried out using Ti (Si) Al and CrAl cathodes at 150 A current, 40 V bias and (Ar)0.1(CH4)0.45(N2)0.45 gas mixture for 50 min. Evaluations were conducted by OM, FESEM, AFM, XRD, nano and micro-indenters, and pin-on-disk tribometer. The uniform films with an about 2.5 μm thickness, and 11.7 and 9.5 nm crystallite size values were respectively formed on the Ti-Al-Cr-C-N and Ti-Al-Cr-(Si)-C-N coated specimens. Surface hardness of the Ti-Al-Cr-C-N and Ti-Al-Cr-Si-C-N-coated samples was respectively obtained 8.7 and 10.8 GPa compared to 2.16 GPa for the un-coated substrate. Roughness (RMS), reduced modulus (E) and H/E ratio related to the Si-incorporated film were respectively determined 4.6 nm, 477 GPa and 0.081 than that of the 9.7 nm, 364 GPa and 0.075 for the Si-emptied film. Tribological properties were significantly enhanced by both the films particular the Si-incorporated kind.
    Keywords: tool steel, Ti-Al-Cr-(Si)-C-N, microstructure, tribological behavior
  • Khalil Gheisari, Mohammad Reza Abasi Pages 81-92
    Dissimilar metals friction welding of austenitic–martensitic stainless steels is commonly used in order to manufacture engine valves in the automobile industry. In this study, X53CrMnNiN219 (austenitic stainless steel) and X45CrSi93 (martensitic stainless steel) valve steel rods were welded by friction welding process. The welded joint was then heat treated at 760 0C for 60 min. Mechanical properties of the welded and heat treated samples were identified by means of microhardness and tensile tests. The microstructure of the weld and the fracture surface of the tension samples were investigated by optical microscopy and scanning electron microscopy. Fractographic evaluations also were performed by using scanning electron microscopy. According to the findings, due to the higher thermal conductivity and lower strength of the martensitic stainless steel, a larger upset and a broader heat affected zone is observed in the martensitic side. Furthermore, formation of non-tempered martensite with the maximum hardness of 880 HV in the heat affected zone (HAZ) of the martensitic stainless steel side makes as-welded material susceptible to brittle fracture as detected by fractographic examinations. Nevertheless, a successfully transition from brittle to ductile behavior is observed by the post-weld heat treatment at 760 0C for 60 min.
    Keywords: Dissimilar metals welding, Friction welding, Heat treatment, Upset zone, X53CrMnNiN219 austenitic stainless steel