Journal of Metallurgy The latest articles from Hindawi Publishing Corporation © 2015 , Hindawi Publishing Corporation . All rights reserved. Effect of Processing Parameters on the Mechanical Properties of Heavy Section Ductile Iron Mon, 26 Jan 2015 13:06:51 +0000 The main objective of the current work is to investigate the influence of different inoculation conditions on the microstructure and mechanical properties of heavy section ductile iron (DI) castings. Inoculation treatment was done via one step and double step treatments with different amounts of inoculants. The mechanical properties of the fabricated samples were evaluated. The best inoculation procedure in terms of graphite nodules characteristics and mechanical properties was double inoculation with 0.8% inoculants added at first and 0.2% in the late inoculation step. The presence of Sb in one of the cast alloys controlled the growth of graphite nodules in these heavy section ductile iron castings; however low impact toughness was recorded. The matrix structure of ductile cast iron showed a significant influence not only on the strength and impact properties but also on the fracture mode during testing. Mohamed Mahmoud Mourad, Shimaa El-Hadad, Mervat Mohamed Ibrahim, and Adel Abdelmonem Nofal Copyright © 2015 Mohamed Mahmoud Mourad et al. All rights reserved. Mathematical Analysis of the Effect of Iron and Silica on the Reduction Performance of Manganese Ores Thu, 01 Jan 2015 13:04:48 +0000 In the current study, a factorial design is used to investigate the effect of total iron and silica on the metallurgical performance of different grades of manganese ores. The derived mathematical formulations are applied to estimate the reduction disintegration index (RDI+6.3, RDI+3.15, and RDI−0.5), reduction index (total reduction index (RIT), manganese reduction index (RIM), and iron reduction index (RIF)), and softening-melting property (start of softening (), end of softening (), start of melting (), and end of melting ()) of manganese ores. The RDI+6.3 and RDI+3.15 are increased with the individual effect of SiO2 and the interaction effect of iron with silica, while they are decreased as the total iron increased. The high-Fe high-SiO2 manganese ore showed the highest RIT and RIF. The RIM was almost identical in all manganese ores. The presence of high content of SiO2 resulted in a narrow softening range (62–83°C), while the high-Fe high-SiO2 manganese ore exhibited a wider softening range (135–140°C). The melting range was very small in high-Fe low-SiO2 (3–16°C) and high-Fe high-SiO2 (6–8°C) manganese ores, while the low-Fe low-SiO2 manganese ore showed wider melting range (72–74°C). The derived mathematical models are in a good agreement with the experimental results. The calculations are carried out using Matlab program. S. Ghali and E. A. Mousa Copyright © 2015 S. Ghali and E. A. Mousa. All rights reserved. On the Designing, Efficiency, and Stirring Force of an Induction Coil for the Processing of Prototype Al Based Nanocomposites Wed, 31 Dec 2014 00:10:21 +0000 Induction melting could be a potential fabrication method for aluminum matrix nanocomposites, owing to its characteristics stirring action and rapid heating. In the present work, an induction coil for small scale composite fabrication was designed through geometric, thermal, and electromagnetic analyses. Subsequently, the designed coil was simulated for its thermal efficiency and stirring force using finite element method magnetics software. The designed coil yielded more than 60% of the total energy supplied into thermal efficiency with a stirring force <3 mN, which could be significant for efficient melting and stirring to fabricate the aluminum matrix nanocomposites. Muhammad Mansoor and Muhammad Shahid Copyright © 2014 Muhammad Mansoor and Muhammad Shahid. All rights reserved. Mathematical Analysis of the Reduction of Wüstite at Different Basicity Using Factorial Design Tue, 16 Dec 2014 14:13:52 +0000 Numerical prediction is performed on the reduction of wüstite under simulated blast furnace conditions using factorial design approach. Wüstite sinter samples with different basicity (0.5, 1.0, and 2.0) are reduced with a gas mixture consisting of 30% CO, 10% H2, 5% CO2, and 55% N2 at 950–1100°C. In all cases, the reduction degree of wüstite increased with basicity and temperature. A 23 factorial design is applied to derive a regression model based on the experimental data of acidic (CaO/SiO2 = 0.5) and basic (CaO/SiO2 = 2.0) wüstite which is reduced at 950°C and 1100°C for 5 and 35 min. The developed mathematical model is applied to predict the reduction degree of wüstite at different basicity (0.5, 1.0, and 2.0), interval of time (5–35 min), and temperatures (950, 1000, 1050°C, and 1100°C). In general, the results of the driven models are found to be in good agreement with the experimental data of reduction of wüstite in many cases. The MATLAB program is used to carry out the required calculations. E. A. Mousa Copyright © 2014 E. A. Mousa. All rights reserved. Artificial Neural Networks Investigation of Indentation Force Effects on Nano- and Microhardness of Dual Phase Steels Sun, 07 Dec 2014 07:27:46 +0000 Nanoindentation test results on different grain sizes of dual phase (DP) steels are used to train artificial neural networks (ANNs). With selection of ferrite and martensite grain size, martensite volume fraction (MVF), and indentation force as input and microhardness, ferrite, and martensite nanohardness as outputs, six different ANNs are trained according to normalized datasets to predict hardness and their tolerances. A graphical user interface (GUI) is developed for a better investigation of the trained ANN prediction. The response of the ANN is analyzed in five case studies. In each case the variation of two input parameters on the output is analyzed when the other input parameters are kept constant. Reliable and reasonable results of ANN predictions are achieved in each case. A. Fotovati, J. Kadkhodapour, and S. Schmauder Copyright © 2014 A. Fotovati et al. All rights reserved. Closed Die Hammer Forging of Inconel 718 Mon, 01 Dec 2014 06:24:38 +0000 A method for the production of Inconel 718 (IN-718) hemispherical domes by closed die hammer forging is proposed. Different combination of operations employed for production are as follows: (i) preforging + final forging + air cooling, (ii) preforging + final forging + controlled cooling, (iii) direct forging + controlled cooling, and (iv) direct forging + air cooling. Last three combinations yielded a crack free hemispherical dome. The forged hemispherical domes were solution annealed at 980°C for 1 h and air cooled. The grain size of the domes at all locations was finer than ASTM No 4. Mechanical properties of the forged dome in solution treated and aged condition (STA) were better than feedstock used. S. Chenna Krishna, Satish Kumar Singh, S. V. S. Narayana Murty, Ganji Venkata Narayana, Abhay K. Jha, Bhanu Pant, and Koshy M. George Copyright © 2014 S. Chenna Krishna et al. All rights reserved. Aluminium AA6061 Matrix Composite Reinforced with Spherical Alumina Particles Produced by Infiltration: Perspective on Aerospace Applications Sun, 30 Nov 2014 00:10:04 +0000 Metal matrix composites, based on AA6061 reinforced with 60 vol% spherical particles, were produced by gas pressure infiltration and characterized for hardness, impulse excitation modulus, tensile properties (at room temperature and at 250°C), and machining. It was experimentally demonstrated that the novel alumina powder used in the present work does not react with the liquid Mg-containing matrix during the infiltration process. The AA6061 matrix therefore retains its ability to be strengthened by precipitation heat treatment. The latter behaviour combined with the spherical particle shape confers the studied material higher strength and better machinability in comparison with similar composites produced using standard angular alumina particles. The overall features are promising for applications in the aerospace industry, where light and strong materials are required. Claudio Bacciarini and Vincent Mathier Copyright © 2014 Claudio Bacciarini and Vincent Mathier. All rights reserved. Influence of Vanadium and Cast Temperature on Nitrogen Solubility of Stainless Steel Thu, 20 Nov 2014 00:00:00 +0000 Three stainless steel grades with different vanadium content were produced in open induction furnace. The base chemical composition of investigated stainless steel has contained 18.48–18.75% Cr, 5.17–5.62% Mn, 2.47–2.58% Mo, and 6.39–6.64% Ni. The vanadium contents of the three stainless steel grades were 0.009%, 0.112%, and 0.189%. The proposed stainless steels were casted at temperatures 1753 K and 1833 K. The nitrogen contents were determined for the produced steel grades at every cast temperature. The determined nitrogen contents were compared with those calculated from the developed equation of Grigorenko and Pomarin. The influence of cast temperature and vanadium content on nitrogen solubility was investigated. Interpretation between experimental and calculated nitrogen content was carried out. Increasing vanadium content and decreasing cast temperature were found to have positive significant effect on the nitrogen solubility. There were great deviations between experimental results and those calculated by Grigorenko and Pomarin equation. Saeed Ghali Copyright © 2014 Saeed Ghali. All rights reserved. Mathematical Model of Prediction of Nitrogen Pickup in Nitriding Process of Low Carbon Ferromanganese Thu, 17 Jul 2014 12:34:18 +0000 Low carbon ferromanganese was nitrided through gas-solid reaction. The nitriding process has been carried out on lab scale at temperature range 800°C–950°C at different nitrogen pressures. Temperature, time, and partial nitrogen pressure of nitriding process of fine low carbon ferromanganese were investigated. Nitrogen content, in weight percent, was more than 9%. MATLAB software was used to derive mathematical model to predict nitrogen content as a function of temperature and nitrogen pressure. According to derived model, nitrogen content can be calculated by the following equation: , where, T is nitriding temperature in K and P is nitrogen pressure in bar. The experimental results are in good agreement with the predicted results. The results showed that nitrogen content, at steady state, is mainly depending on temperature and pressure of nitriding process. MATLAB is a good tool to make precision mathematical model. Saeed Ghali Copyright © 2014 Saeed Ghali. All rights reserved. Microstructure and Microhardness Evolutions of High Fe Containing Near-Eutectic Al-Si Rapidly Solidified Alloy Sun, 25 May 2014 08:34:07 +0000 Al-11 wt.% Si-11 wt.% Fe (11.29 at.% Si-5.6 at.% Fe) melt was rapidly solidified into ribbons and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and microhardness technique. The Rietveld X-ray diffraction analysis was applied successfully to analyze microstructure and phase precipitations. On the basis of the aluminum peak shifts measured in the XRD scans, a solid solubility extension value of 1 at.% Si in -Al was determined. SEM investigations confirmed presence of a spherical shape -phase particles in addition to needle and spherical shape -phase particles with contents of 1.1 wt.% and 10.1 wt.% as deduced by XRD analysis. During prolonged annealing process at 350°C/25 h, -phase disappeared, -phase content increased to 30 wt.%, and Si presence becomes more evident as deduced by XRD analysis. EDS analysis confirmed that these particles observed in the as-melt spun alloy are of lower Fe content comparing to those usually observed in the as-cast counter-part alloy. Besides, the length distribution of needle shape -particles has been shortened to be diverse from 1 to 5 μm. The as-melt spun ribbons exhibited enhancement of hardness to 277 HV and further increased during heat treatment (150°C/12 h) to 450 HV. This improvement of microstructure and hardness are the influence of microstructural refinement and modification obtained during the rapid solidification process. Emad M. Ahmed and M. R. Ebrahim Copyright © 2014 Emad M. Ahmed and M. R. Ebrahim. All rights reserved. Some Thiophene Derivatives as Corrosion Inhibitors for Carbon Steel in Hydrochloric Acid Wed, 07 May 2014 11:40:57 +0000 Corrosion inhibitive performance of some thiophene derivatives during the acidic corrosion of carbon steel surface in 1 M HCl was investigated by chemical technique (weight loss) and electrochemical techniques (potentiodynamic polarization, electrochemical frequency modulation, and electrochemical impedance spectroscopy). The effect of temperature on the corrosion rate was investigated by the weight loss method, and some thermodynamic parameters for corrosion and adsorption processes were determined and discussed. The results show that the inhibition efficiency increased with the increase in inhibitor concentration and temperature. The adsorption of thiophene derivatives on the carbon steel surface obeys Langmuir adsorption isotherm. The obtained results indicated that the investigated compounds are chemically adsorbed on the steel surface. Potentiodynamic polarization studies showed that these compounds are mixed-type inhibitors and the results obtained from the techniques are in good agreement. A. S. Fouda, A. A. Attia, and A. A. Negm Copyright © 2014 A. S. Fouda et al. All rights reserved. Heat Treatment in High Chromium White Cast Iron Ti Alloy Tue, 29 Apr 2014 07:54:36 +0000 The influence of heat treatment on microstructure and mechanical properties of high chromium white cast iron alloyed with titanium was investigated. The austenitizing temperatures of 980°C and 1150°C for 1 hour each followed by tempering at 260°C for 2 hours have been performed and the effect of these treatments on wear resistance/impact toughness combination is reported. The microstructure of irons austenitized at 1150°C showed a fine precipitate of secondary carbides (M6C23) in a matrix of eutectic austenite and eutectic carbides (M7C3). At 980°C, the structure consisted of spheroidal martensite matrix, small amounts of fine secondary carbides, and eutectic carbides. Titanium carbides (TiC) particles with cuboidal morphology were uniformly distributed in both matrices. Irons austenitized at 980°C showed relatively higher tensile strength compared to those austenitized at 1150°C, while the latter showed higher impact toughness. For both cases, optimum tensile strength was reported for the irons alloyed with 1.31% Ti, whereas maximum impact toughness was obtained for the irons without Ti-addition. Higher wear resistance was obtained for the samples austenitized at 980°C compared to the irons treated at 1150°C. For both treatments, optimum wear resistance was obtained with 1.3% Ti. Khaled M. Ibrahim and Mervat M. Ibrahim Copyright © 2014 Khaled M. Ibrahim and Mervat M. Ibrahim. All rights reserved. Influence of the Rate and Degree of Deformation on the Texture, Structure and Mechanical Properties of Steel Mon, 24 Mar 2014 16:57:17 +0000 The tests of uniaxial tensile by 10, 20, and 30% at strain rates of 0.1, 1, 60, 120, and 300 mm/min in rolling direction and transverse direction of recrystallized cold-rolled low-carbon steel sheets were carried out. The effect of rate and degree of deformation on the texture, structure, and mechanical properties were studied. The texture transformations and the growth of the anisotropy of mechanical properties with increasing strain rate up to 120 mm/min are explained by the effect of crystallographic intragranular slip and twinning of deformation mechanism. The further increase of deformation rate leads to texture scattering and decreasing of properties anisotropy, which are bound to the difficulty of intragranular sliding and activation of grain boundary sliding. V. V. Usov, N. M. Shkatulyak, A. A. Bryukhanov, and D. Fasmann Copyright © 2014 V. V. Usov et al. All rights reserved. Experimental Study of the Al-Mg-Sr Phase Diagram at 400°C Tue, 18 Mar 2014 07:39:07 +0000 The Al-Mg-Sr system is experimentally studied at 400°C using EPMA and XRD techniques. It was determined that the intermetallic phases in the Al-Mg-Sr system have a tendency to form extended substitutional solid solutions. Two ternary phases were found in this system. Solubility limits of binary and ternary phases were determined and the phase equilibria among phases were established. The isothermal section of the Al-Mg-Sr system at 400°C has been constructed using results of the phase analysis and experimental literature data. D. Kevorkov, M. Medraj, M. Aljarrah, Jian Li, E. Essadiqi, P. Chartrand, and C. Fuerst Copyright © 2014 D. Kevorkov et al. All rights reserved. Progress in Wettability Study of Reactive Systems Wed, 12 Mar 2014 00:00:00 +0000 A review of various factors affecting wetting and spreading has been presented. Various methods for wettability studies and critical issues concerning contact angle measurement are discussed. Reactive wetting has been given a special attention in the paper and recent developments in this area are summarized and discussed. Although advanced understanding of nonreactive wetting is currently available in the literature, complete understanding of reactive wetting is still lacking due to the complexity of the phenomenon. To date, there is no single model that is generally applicable to all reactive wetting systems. Reaction between the liquid drop and substrate can take the form of dissolution, intermetallic formation, or combination of both processes. Factors affecting wettability have been summarized and discussed as well as the major available techniques to investigate wetting behaviour. Bolarinwa Komolafe and Mamoun Medraj Copyright © 2014 Bolarinwa Komolafe and Mamoun Medraj. All rights reserved. Characteristics of Anodized Layer in Investment Cast Ni50Ti50 Shape Memory Alloy Tue, 25 Feb 2014 09:30:57 +0000 NiTi shape memory alloys are promising implant materials due to their shape memory effect and super elasticity. In the current study, some Ni50Ti50 (mass %) SMAs samples were prepared by investment casting. These samples were then anodized and thermally treated to improve the surface properties. A fully saturated oxide layer was obtained. The structure and hardness properties of the anodized surfaces were then investigated. A hard porous layer with no free Ni atoms could be obtained which can be used as prebiomimetic surface for biological application. Shimaa H. El-Hadad, Khaled M. Ibrahim, and Lothar Wagner Copyright © 2014 Shimaa H. El-Hadad et al. All rights reserved. Microstructural Characterization and Corrosion Behavior of Electroless Ni-Zn-P Thin Films Mon, 27 Jan 2014 07:41:13 +0000 Ternary Ni-Zn-P alloy thin films were electrolessly deposited on a carbon steel substrate from sulphate alkaline baths. The effect of deposition bath composition and process duration on the physical-chemical and corrosion characteristics of the obtained thin films was investigated. The thin films were characterized by EDAX analysis techniques and scanning electronic microscopy. Corrosion tests were performed in 3.5% sodium chloride solution and the corrosion current values were determined to be 4–12 μA, comparative to 15 μA for the uncoated steel sample. Ionuţ Constantin Copyright © 2014 Ionuţ Constantin. All rights reserved. Experimental Study of the Interaction between Recrystallization and Precipitation Processes of an AA8011 Commercial Alloy Wed, 22 Jan 2014 14:59:07 +0000 Phase changes in a commercial AA8011 alloy from different initial microstructure conditions were studied using thermoelectric power (), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM) techniques with the purpose of obtaining evidence of the interaction between recovery-precipitation and recrystallization-precipitation processes occurring during nonisothermal heating at different rates. Thermoelectric power and its thermal derivative reflect this evidence by a displacement of the characteristic precipitation peaks, the recovery and recrystallization contributions remaining masked by the strong incidence of the iron precipitation on that property, while DSC measurements detect the emergence of new peaks not observed on thermograms of homogenized samples. An exhaustive study of these peaks permits direct differentiation between precipitation and recovery-recrystallization contributions. TEM confirms the interaction between both processes by means of local observations. Ney José Luiggi, María Valera, Jesús P. Rodriguez, and José Prin Copyright © 2014 Ney José Luiggi et al. All rights reserved. Columnar-to-Equiaxed Transition in Metal-Matrix Composites Reinforced with Silicon Carbide Particles Mon, 30 Dec 2013 12:13:48 +0000 The present work is focused on the study of the effect of directional heat extraction on the silicon-carbide (SiC) distribution in zinc-aluminum matrix composites (MMCs) and on the columnar-to-equiaxed (CET) position in directionally solidified samples. To this end, a ZA-27 alloy matrix was reinforced with ceramic particles of SiC and vertically directionally solidified. The cooling rates, temperature gradients, and interphase velocities were then measured, and their influence on the solidification microstructure of the MMCs was analyzed. The recalescence detected and measured during the equiaxed transition was of the order of 3.5°C to 1.1°C. The values of the temperature gradients reached a minimum during the CET and were even negative in most cases (between −3.89 K and 0.06 K). The interphase velocities varied between 0.07 mm/s and 0.44 mm/s at the transition. Also, the presence of ceramic particles in ZA-27 alloys affected the thermodynamic local conditions and the kinetics of nucleation, producing a finer microstructure. Alicia E. Ares and Carlos E. Schvezov Copyright © 2013 Alicia E. Ares and Carlos E. Schvezov. All rights reserved. Factorial Analysis of Welding Current Influence on Heat Affected Zone Hardness of Cast Iron, Aluminium, and Mild Steel Weldments Cooled in Palm Oil Wed, 20 Nov 2013 12:00:01 +0000 Factorial analysis of heat affected zone hardness of some metals was evaluated. Three models were derived and used as tools for evaluating the welding current influence on the predictability of HAZ hardness in aluminium, cast iron, and mild steel weldments similarly cooled in palm oil. It was discovered that on welding these materials, and similarly cooling their respective weldments in palm oil, the model predicts aluminium weldment HAZ hardness by multiplying the determined general current product rule (GCPR) with the ratio: HAZ hardness product of cast iron and mild steel/HAZ hardness sum of cast iron and mild steel . Computational analysis of experimental and model-predicted results indicates that aluminium, cast iron, and mild steel weldment HAZ hardness per unit welding current as evaluated from experiment and derived model are 3.3917, 4.8333, and 2.7944 and 3.3915, 4.8335, and 2.7946 (VHN) A−1, respectively. Deviational analysis shows that the maximum deviation of model-predicted HAZ hardness from the experimental results is less than 0.007%. This invariably implies over 99.99 % confidence level for the derived models. C. I. Nwoye, J. U. Odo, E. M. Ameh, and S. O. Nwakpa Copyright © 2013 C. I. Nwoye et al. All rights reserved. Preparation of Niobium Metal Powder by Two-Stage Magnesium Vapor Reduction of Niobium Pentoxide Mon, 19 Aug 2013 11:48:25 +0000 Magnesium vapor reduction of niobium pentoxide was studied using a laboratory system. Niobium powder was prepared by the magnesium vapor reduction at 1123 K for 5 hours and it contained about 8 mass % oxygen. However, the oxygen concentration could be decreased to 0.65% when it was prepared by double-step reduction by magnesium vapor and a chemical treatment. Controlled and diluted supply of magnesium vapor to the reaction front has averted excess heat generation at the reaction front and thereby fine particles were produced. Effects of various factors on the vapor reduction process were studied and discussed. T. Satish Kumar, S. Rajesh Kumar, M. Lakshmipathi Rao, and T. L. Prakash Copyright © 2013 T. Satish Kumar et al. All rights reserved. Inhibition Effect of Substituted Thiadiazoles on Corrosion Activity of N80 Steel in HCl Solution Thu, 18 Apr 2013 16:11:07 +0000 The inhibition effect of some prepared compounds, namely, thiadiazole derivatives, on N80 steel corrosion in 15% HCl solutions has been studied by using the weight loss, electrochemical polarization, and electrochemical impedance spectroscopy techniques. It was found that the inhibition efficiency of the thiadiazole derivatives, namely, 2-amino-5-(4-methoxyphenyl)-1,3,4-thiazole (AMPT), 2-amino-5-phenyl-1,3,4-thiazole (APT), and 2-amino-5-(4-chlorophenyl)-1,3,4-thiazole (ACPT), increases with the increase in concentration. Inhibition efficiency follows the order AMPT > APT > ACPT. The effect of temperature on the corrosion was investigated by the weight loss method, and some thermodynamic parameters were calculated. The inhibitive action may be attributed to the adsorption of inhibitor molecules on the active sites of the metal surface following Langmuir adsorption isotherm. Polarization measurements indicated that thiadiazole derivatives act as mixed-type corrosion inhibitor. The adsorption of thiadiazole derivatives on N80 surface exposed to inhibitor-containing solutions was confirmed using SEM and FT-IR spectra. M. Yadav, Sumit Kumar, and Debasis Behera Copyright © 2013 M. Yadav et al. All rights reserved. Mathematical Models for the Novel Cathode Convexes in a Reduction Cell Sun, 31 Mar 2013 18:00:09 +0000 A less magnitude of liquid aluminum deformation is required to shorten the anode-cathode distance so as to lower the electric energy consumption of the aluminum reduction cell. A mathematical model aimed to describe the electrolyte/aluminum two-phase flow in reduction cells, based on the computational fluid dynamics method, was developed to study the impacts of the cathode convexes on the electrolyte/aluminum interface deformation. The results showed that the magnitude of the two-phase interface deformation was reduced for about 17.2% with the novel cathode convexes; while at the same time, the washout of the melt on the ledge was also enhanced. Z. He, T. Xia, W. Xiong, Q. Shen, and B. Li Copyright © 2013 Z. He et al. All rights reserved. XRD and DTA Analysis of Developed Agglomerated Fluxes for Submerged Arc Welding Mon, 11 Mar 2013 17:43:32 +0000 A unique study of structural and chemical analysis of crystalline phases in developed agglomerated fluxes was carried out. Thirty-two fluxes were developed by using a mixture of oxides, halides, carbonates, silicates, and ferroalloys for submerged arc welding. The present paper focuses on only ten (out of thirty-two) fluxes which were analyzed by X-ray diffraction (XRD) to know the different types of oxides formed and changed in oxidation number of metallic centers after sintering process at around 850∘C. To know the effect of temperature over phase transformation and melting of different compounds, differential thermal analysis (DTA) was carried out from 1000 to 1400∘C. This study aims to know the quantity of ions present (percentage) and melting behavior of developed agglomerated fluxes for submerged arc welding process. Ajay Kumar, Hari Singh, and Sachin Maheshwari Copyright © 2013 Ajay Kumar et al. All rights reserved. Fabrication of Single-Phase NiTi by Combustion Synthesis of Mechanically Activated Powders Sun, 30 Dec 2012 15:03:21 +0000 Single-phase NiTi was fabricated through the thermal explosion mode of combustion synthesis of mechanically activated powders. Combustion and ignition temperatures of combustion synthesis were investigated in different milling times. In this process, equiatomic powder mixtures of nickel and titanium were activated by planetary ball mill and pressed into disk-shaped pellets then heated in a tube furnace, while temperature-time profile was recorded. X-ray diffraction analysis (XRD) was performed on milled powders as well as synthesized samples. Scanning electron microscopy (SEM) was also used to study the microstructural evolution during milling. The results showed that there was a threshold milling time to obtain single-phase NiTi. It was also seen that the ignition temperature and combustion temperature were reduced significantly by increasing milling time. S. Mousavi Nasab, M. Aboutalebi, S. H. Seyedein, A. Molavi Kakhki, and J. Vahdati Khaki Copyright © 2012 S. Mousavi Nasab et al. All rights reserved. Effect of Diacetyl Monoxime Thiosemicarbazone on the Corrosion of Aged 18 Ni 250 Grade Maraging Steel in Sulphuric Acid Solution Mon, 17 Dec 2012 08:42:04 +0000 The corrosion inhibition of the aged 18 Ni 250 grade maraging steel in 0.5 M sulphuric acid by diacetyl monoxime thiosemicarbazone (DAMTSC) at 303–323 K has been investigated by potentiodynamic polarization, EIS, and SEM techniques. Good inhibition efficiency of DAMTSC was revealed even at low concentrations, which increased with the increase in DAMTSC concentration and decreased with the increase in temperature. The activation energies, , as well as other thermodynamic parameters (; ; ), were evaluated and discussed. The adsorption of DAMTSC on the aged maraging steel surface was found to obey the Langmuir adsorption isotherm model and shows mixed type inhibition behavior. T. Poornima, Jagannath Nayak, and A. Nityananda Shetty Copyright © 2012 T. Poornima et al. All rights reserved. Mechanical Response of Al-1.09Mg2Si Alloy under Varying Mould and Thermal Ageing Conditions Tue, 11 Dec 2012 17:16:36 +0000 Samples of the 6063 (Al-1.09Mg2Si) alloy ingot were melted in a crucible furnace and cast in metal and sand moulds, respectively. Standard tensile, hardness, and microstructural test specimens were prepared from cast samples, solution treated at 520∘C, soaked for 6 hrs, and immediately quenched at ambient temperature in a trough containing water to assume a supersaturated structure. The quenched specimens were then thermally aged at 175∘C for 3–7 hrs. Results show that at different ageing time, varied fractions of precipitates and intermetallics evolved in the specimens’ matrices which affect the resulting mechanical properties. The metal mould specimens aged for four hours (MTA-4) exhibited superior ultimate tensile strength of 247.8 MPa; microhardness, 68.5 HV; elongation, 28.2% . It is concluded that the extent of improvement in mechanical properties depends on the fractions, coherence, and distribution of precipitates along with the type of intermetallics developed in the alloy during ageing process. O. I. Sekunowo, G. I. Lawal, and S. O. Adeosun Copyright © 2012 O. I. Sekunowo et al. All rights reserved. Precipitation of Phase Using General Diffusion Equation with Comparison to Vitek Diffusion Model in Dissimilar Stainless Steels Thu, 22 Nov 2012 10:38:36 +0000 This study performs a precipitation examination of the phase using the general diffusion equation with comparison to the Vitek model in dissimilar stainless steels during multipass welding. Experimental results demonstrate that the diffusivities (, , and ) of Cr, Ni, and Si are higher in -ferrite than (, , and ) in the phase, and that they facilitate the precipitation of the σ phase in the third pass fusion zone. The Vitek diffusion equation can be modified as follows: . Chih-Chun Hsieh and Weite Wu Copyright © 2012 Chih-Chun Hsieh and Weite Wu. All rights reserved. Internal Demagnetizing Factor in Ferrous Metals Mon, 05 Nov 2012 15:11:06 +0000 Modelling the saturation major loop of a ferrous metal produces the intrinsic magnetization parameters; fitting the measured commutation curve, however, can yield different results. The relation of the intrinsic loci of the vertices of the minor loops () to the experimental curve () is investigated. The two-way transformation between the two curves is formulated in closed mathematical form with the help of the internal demagnetization factor, . The method is applied to four ferrous metals, with widely different intrinsic properties (soft nonoriented Fe-Si steel, normalized low carbon steel, and Finemet in nanocrystalline and amorphous state) supporting the predictions of the proposal. The developed relationship is model independent and it is shown that the factor depends linearly on coercivity based on experimental evidence. Jenő Takács, György Kovács, and Lajos K. Varga Copyright © 2012 Jenő Takács et al. All rights reserved. Mutual Influence of Special Components in Baotou Steel Blast Furnace Slag on the Crystallization Behavior of Glass Wed, 17 Oct 2012 10:10:18 +0000 In the process of glass-ceramics prepared with Baotou steel blast furnace slag, quartz sand, and other raw materials by melting method, the mutual influence of the special components such as CaF2, REXOY, TiO2, K2O, and Na2O in the blast furnace slag on the crystallization behavior of parent glass was investigated using differential thermal analysis (DTA) and X-ray diffraction (XRD). The results show that the special components in slag can reduce the crystallization temperature and promote crystallization of glass phase, which belongs to surface crystallization of glass, and they cannot play the role of the nucleating agent; the major crystal phase composed of diopside, diopside containing aluminum and anorthite, is slightly different from the expected main crystal phase of diopside. Therefore, the nucleating agents of proper species and quantity must be added into the raw materials in order to obtain glass-ceramics. The results have important theoretical guidance meaning for realizing industrial production of Baotou steel blast furnace slag glass-ceramics preparation. Yici Wang, Qi Jiang, Guoping Luo, Wenwu Yu, and Yan Ban Copyright © 2012 Yici Wang et al. All rights reserved.