http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2013 , Hindawi Publishing Corporation . All rights reserved. Thu, 18 Apr 2013 16:11:07 +0000 http://www.hindawi.com/journals/jm/2013/256403/ 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. Sun, 31 Mar 2013 18:00:09 +0000 http://www.hindawi.com/journals/jm/2013/196891/ 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. Mon, 11 Mar 2013 17:43:32 +0000 http://www.hindawi.com/journals/jm/2013/827491/ 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. Sun, 30 Dec 2012 15:03:21 +0000 http://www.hindawi.com/journals/jm/2012/153841/ 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. Mon, 17 Dec 2012 08:42:04 +0000 http://www.hindawi.com/journals/jm/2012/723687/ 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. Tue, 11 Dec 2012 17:16:36 +0000 http://www.hindawi.com/journals/jm/2012/921235/ 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. Thu, 22 Nov 2012 10:38:36 +0000 http://www.hindawi.com/journals/jm/2012/154617/ 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. Mon, 05 Nov 2012 15:11:06 +0000 http://www.hindawi.com/journals/jm/2012/752871/ 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. Wed, 17 Oct 2012 10:10:18 +0000 http://www.hindawi.com/journals/jm/2012/954021/ 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. Tue, 02 Oct 2012 12:01:45 +0000 http://www.hindawi.com/journals/jm/2012/624650/ Mould filling ability characteristic has been influencing the liquid metal flow, heat transfer, and solidification there by affecting the quality of aerospace castings. Mould filling is a critical parameter in the production of sound and quality castings, especially in the case of complex-shaped castings where section thickness is varying considerably. The mould filling ability of aluminium alloys LM6 and LM25 has been studied in the present investigation. Experimentation has been carried out using orthogonal array experimental layout. The process parameters studied in the present investigation are alloy composition, sand fineness, mould coating, and pouring temperature. The mould filling ability of selected aluminium alloy has been studied using pin test piece with cylindrical cores. The results from experimentation are analyzed to find the influence of the process parameters on mould filling ability. Based on the above, LM6 alloy has been found to have better mould filling ability characteristics and the analysis of variance has also revealed the same optimum factor combination. Samavedam Santhi, S. B. Sakri, Dharwada Hanumantha Rao, and Srinivasan Sundarrajan Copyright © 2012 Samavedam Santhi et al. All rights reserved. Wed, 19 Sep 2012 08:25:20 +0000 http://www.hindawi.com/journals/jm/2012/294874/ Hugh J. McQueen, Enrico Evangelista, Michael E. Kassner, and Chong Soo Lee Copyright © 2012 Hugh J. McQueen et al. All rights reserved. Sun, 29 Jul 2012 10:03:36 +0000 http://www.hindawi.com/journals/jm/2012/517230/ The statistical relaxation (SR) simulation has been conducted to study the behavior of simplexes and bubbles (BB) in amorphous Co metal containing 2×105 atoms. The simulation reveals that the fraction of 4-simplex increases and 𝑛-simplex (𝑛>4) decreases depending upon relaxation degree. The simulation found that a large number of BB vary upon relaxation degree, which could play a role of diffusion vehicle for Co atoms in amorphous matrix. The idea of the diffusion mechanism in amorphous metal is described as follows: the elemental atomic movement includes a jump of neighboring atom into the BB and then a collective displacement of a large number of atoms around BB. P. H. Kien, H. V. Hue, and P. K. Hung Copyright © 2012 P. H. Kien et al. All rights reserved. Sun, 20 May 2012 11:42:11 +0000 http://www.hindawi.com/journals/jm/2012/841901/ The transformation of iron carbide cementite was investigated on spheroidal graphite containing different contents of manganese. The isothermal maintain were carried out at 600, 650, 700, and 750°C for periods of up to one hour. It was observed that the kinetics of graphitization is slowed even more than cast iron rich in manganese. Jalel Briki and S. Ben Slima Copyright © 2012 Jalel Briki and S. Ben Slima. All rights reserved. Tue, 08 May 2012 14:22:48 +0000 http://www.hindawi.com/journals/jm/2012/303756/ Friction stir welding (FSW), a solid-state joining technique, is being extensively used in similar as well as dissimilar joining of Al, Mg, Cu, Ti, and their alloys. In the present study, friction stir welding of two aluminium alloys—AA6061 and AA5052—was carried out at various combinations of tool rotation speeds and tool traverse speeds. The transverse cross-section of the weld was used for optical as well as electron microscopy observations. The microstructural studies were used to get an indication of the extent of material mixing both at the macro- and microscales. It was observed that, at the interface region, both materials exhibited similar texture despite the nonrigorous mixing of the materials in the nugget. The extent of interdiffusion of alloying elements at the interface was studied using electron probe microanalysis. The tensile testing evaluation of these specimens showed good mechanical properties. The interdiffusion of alloying elements and development of similar orientations in the nugget could have contributed to the better tensile properties of the friction-stir-welded AA5052-AA6061 specimens. N. T. Kumbhar and K. Bhanumurthy Copyright © 2012 N. T. Kumbhar and K. Bhanumurthy. All rights reserved. Tue, 27 Mar 2012 13:11:45 +0000 http://www.hindawi.com/journals/jm/2012/762125/ This paper reviews results obtained by the research groups developing the low-energy high-current pulsed electron beam (LEHCPEB) in Dalian (China) and Metz (France) on the surface treatment of light alloys. The pulsed electron irradiation induces an ultra-fast thermal cycle at the surface combined with the formation of thermal stress and shock waves. As illustrated for Mg alloys and Ti, this results in deep subsurface hardening (over several 100 μm) which improves the wear resistance. The analysis of the top surface melted surface of light alloys also often witnesses evaporation and condensation of chemical species. This phenomenon can significantly modify the melt chemistry and was also suggested to lead to the development of specific solidification textures in the rapidly solidified layer. The potential use of the LEHCPEB technique for producing thermomechanical treatments under the so-called heating mode and, thus, modify the surface crystallographic texture, and enhance solid-state diffusion is also demonstrated in the case of the FeAl intermetallic compound. X. D. Zhang, S. Z. Hao, T. Grosdidier, J. X. Zou, B. Gao, B. Bolle, N. Allain-Bonasso, Y. Qin, X. N. Li, and C. Dong Copyright © 2012 X. D. Zhang et al. All rights reserved. Thu, 22 Mar 2012 14:15:34 +0000 http://www.hindawi.com/journals/jm/2012/539823/ The modelling of an axisymmetric industrial quenched chromium steel bar AISI-SAE 8650H based on finite element method has been produced to investigate the impact of process history on metallurgical and material properties. Mathematical modelling of 1-dimensional line (radius) element axisymmetric model has been adopted to predict temperature history and consequently the hardness of the quenched steel bar at any point (node). The lowest hardness point (LHP) is determined. In this paper hardness in specimen points was calculated by the conversion of calculated characteristic cooling time for phase transformation t8/5 to hardness. The model can be employed as a guideline to design cooling approach to achieve desired microstructure and mechanical properties such as hardness. The developed mathematical model is converted to a computer program. This program can be used independently or incorporated into a temperature history calculator to continuously calculate and display temperature history of the industrial quenched steel bar and thereby calculate LHP. The developed program from the mathematical model has been verified and validated by comparing its hardness results with commercial finite element software results. Abdlmanam S. A. Elmaryami and Badrul Omar Copyright © 2012 Abdlmanam S. A. Elmaryami and Badrul Omar. All rights reserved. Wed, 14 Mar 2012 15:30:30 +0000 http://www.hindawi.com/journals/jm/2012/438659/ The carbide and graphite formation and redistribution of alloy elements during solidification were investigated on high-speed steel (HS) and Ni-hard type cast irons with Nb and V. The crystallization of hypereutectic HSS proceeds in the order of primary MC, γ + MC, γ + M6C, γ + M7C3, and γ +  graphite eutectic, in hypoeutectic alloys proceeds in the order of primary γ, γ + MC, γ + graphite, γ + M6C, and γ + M7C3 eutectic, and in Ni-hard proceeds in the order of primary γ, γ + MC, γ + M3C, and γ +  graphite eutectic. The γ +  graphite eutectic solidifies with the decrease of V, Nb, and Cr and the increase of Si and C contents in residual liquid during solidification. The behavior in graphite forming tendency in the residual liquid is estimated by the parameter ∑𝐶𝑖𝐿𝑚𝑖. The eutectic graphite crystallizes at the solid fraction when ∑𝐶𝑖𝐿𝑚𝑖 takes a minimum value. The amount of graphite increases with the decrease in ∑𝐶𝑖𝐿𝑚𝑖 of initial alloy content in both specimens. Inoculation with ferrosilicon effectively increases the graphite content in both specimens. Sergio Villanueva Bravo, Kaoru Yamamoto, Hirofumi Miyahara, and Keisaku Ogi Copyright © 2012 Sergio Villanueva Bravo et al. All rights reserved. Thu, 08 Mar 2012 15:39:08 +0000 http://www.hindawi.com/journals/jm/2012/385963/ Cylindrical samples of AISI 1020, AISI 316, and AISI 420 steels, with different heights, were simultaneously treated by a new technique of ionic nitriding, entitled cathodic cage plasma nitriding (CCPN), in order to evaluate the efficiency of this technique to produce nitrided layers with better properties compared with those obtained using conventional ionic nitriding technique. This method is able to eliminate the edge effect in the samples, promoting a better uniformity of temperature, and consequently, a smaller variation of the thickness/height relation can be obtained. The compound layers were characterized by X-ray diffraction, optical microscopy, and microhardness test profile. The results were compared with the properties of samples obtained with the conventional nitriding, for the three steel types. It was verified that samples treated by CCPN process presented, at the same temperature, a better uniformity in the thickness and absence of the edge effect. R. R. M. de Sousa, F. O. de Araújo, J. A. P. da Costa, A. de S. Brandim, R. A. de Brito, and C. Alves Jr. Copyright © 2012 R. R. M. de Sousa et al. All rights reserved. Wed, 29 Feb 2012 08:29:42 +0000 http://www.hindawi.com/journals/jm/2012/258021/ Because of the outstanding properties of aluminum, it is widely used in today's advanced technological world. However, its insufficient wear resistance limits its use for commercial and industrial applications. In this study, we performed DC diode plasma carburizing of aluminum in the gas composition of CH4–H2 (20–80%) and at a temperature of about 350°C for 4 and 8 hours. The corrosion properties of the untreated and plasma-carburized samples were evaluated using anodic polarization tests in 3 N HCl solution according to ASTM: G5-94. The metallurgical characteristics were then investigated using XRD and SEM. The results showed that the carburizing process improves the corrosion resistance of treated specimens at low temperature. Somayeh Pirizadhejrandoost, Mehdi Bakhshzad Mahmoudi, Elnaz Ahmadi, and Masoud Moradshahi Copyright © 2012 Somayeh Pirizadhejrandoost et al. All rights reserved. Tue, 14 Feb 2012 10:58:53 +0000 http://www.hindawi.com/journals/jm/2012/176968/ This paper investigates the effect of limestone, bauxite, fluorspar, and quartzite additions on the magnesium recovery in FeSiMg production from dolomite. Also, it illustrates the validation of the previous designed model. According to the model, magnesium content in the product alloy is calculated by the equation [Mg]=(MgO0)[Si0][𝑒𝐾𝑡[(MgO0)−[Si0]]−1]/((MgO0)[𝑒𝐾𝑡[(MgO0)−[Si0]]]−[Si0]), where [Mg] is the concentration of magnesium metal in ferrosilicon magnesium alloy in mol/L, [Si0] and (MgO0) are the initial concentrations of silicon and magnesium oxide in charge in mol/L, 𝑡 is the time in seconds, and 𝐾 is the reaction rate constant (3.26588×10−7 LSec−1 mol−1). The results of the production process are compared with the model results. The deviation between the actual and predicted magnesium content decreases as fluorspar, limestone, and quartzite increase up to 12.8wt.%, 8wt.%, and 8wt.%, respectively, with increase in the amount of the additives, the magnesium content in the produced alloy becomes far from the predicted values. It was found also that the addition of bauxite increases the gap between the actual and predicted values of magnesium content. It was found that the deviation of the actual magnesium content from the predicted depends mainly on the viscosity of the slag. Saeed Ghali, Mamdouh Eissa, and Hoda El-Faramawy Copyright © 2012 Saeed Ghali et al. All rights reserved. Wed, 08 Feb 2012 11:02:27 +0000 http://www.hindawi.com/journals/jm/2012/531915/ The effect of annealing temperature on electrical characteristics of iridium (Ir) and iridium/gold (Ir/Au) Schottky contacts to n-type InGaN have been investigated by means of current-voltage (I-V) and capacitance-voltage (C-V) techniques. It is observed that the barrier height of Ir/n-InGaN and Au/Ir/n-InGaN Schottky diodes increases after annealing at 300∘C for 1 min in N2 ambient compared to the as-deposited. However, the barrier heights are found to be decreased somewhat after annealing at 500∘C for the both Ir and Ir/Au Schottky contacts. From the above observations, it is clear that the optimum annealing temperature for both Ir and Ir/Au Schottky contacts is 300∘C. Moreover, the barrier height (𝜙𝑏), ideality factor (n) and series resistance (𝑅𝑆) are determined using Cheung’s and Norde methods. Besides, the energy distribution of interface state densities are determined from the forward bias I-V characteristics by taking into account the bias dependence of the effective barrier height. Based on the above results, it is clear that both Ir and Ir/Au Schottky contacts exhibit a kind of thermal stability during annealing. V. Rajagopal Reddy, B. Prasanna Lakshmi, and R. Padma Copyright © 2012 V. Rajagopal Reddy et al. All rights reserved. Tue, 07 Feb 2012 15:10:09 +0000 http://www.hindawi.com/journals/jm/2012/638290/ The effect of microstructure on the stress-strain behaviour of pipeline steels was studied. Slow strain rate (2×10−6 s−1) tests were conducted on grade X65 and X100 steels in silicone oil and hydrogen carbonate/carbonate solution. The as-received grade X100 steel at 75∘C showed serrated stress-strain curves. The magnitude of the serrations depended upon the strain rate and test temperature. Annealing at 600∘C or above removes the serrations, but this increased the susceptibility to transgranular cracking in hydrogen carbonate/carbonate solution at potentials below −800 mV (sce). The removal and reformation of banding in pipeline steels were also studied. Ferrite/pearlite becomes aligned during the hot rolling stage of pipe manufacture and causes directionality in crack propagation and mechanical properties. Heat treatments were carried out which show that banding in grade X65 and X100 can be removed above 900∘C. This depends on homogenisation of carbon which also depends on temperature, time, and cooling rate. A. Mustapha, E. A. Charles, and D. Hardie Copyright © 2012 A. Mustapha et al. All rights reserved. Thu, 02 Feb 2012 11:29:46 +0000 http://www.hindawi.com/journals/jm/2012/290873/ Cold pressing (CP) of the amorphous-like Co powder suppressed most of the XRD peaks, in particular the peak along (100) plane. The DSC curve of unmilled CP Co powder has shown a distinct sharp exothermic peak at 615∘C. Upon annealing at 700∘C, only the FCC phase with lattice parameter of 3.51 Å was detected by XRD. Our results implied that the exotherm at 615∘C corresponds to compaction-pressure-assisted HCP to FCC first-order phase transition. The XRD analysis of 30 h milled powder revealed for the first time the FCC phase with 𝑎=3.80 Å. However, due to presence of (100) and (210) peaks, this phase is thought to be FCT with lattice parameters 𝑎=𝑏=3.80 and 𝑐=3.07 Å. Consequently, the high-energy milling carried out in the current work induced for the first time HCP to FCT transition in Co. Upon CP of milled powder, the lattice parameter 𝑎 shrunk from 3.80 to 3.75 Å. However, during annealing of the CP milled Co powder at 750∘C, the FCT to FCC transition occurred, yielding the FCC phase with 𝑎=3.51 Å. A. S. Bolokang, M. J. Phasha, D. E. Motaung, and S. Bhero Copyright © 2012 A. S. Bolokang et al. All rights reserved. Wed, 01 Feb 2012 08:27:07 +0000 http://www.hindawi.com/journals/jm/2012/989834/ Microstructure evolution of Ti-6Al-4V alloy during hot backward extrusion process was simulated with the combined approaches of finite element method (FEM) and microstructure prediction model. From experimental analysis, it can be found that the change of microstructure during hot forming process of titanium alloy has a close relation to 𝛼/𝛽 phase transformation and grain growth behaviour. A microstructure prediction model was established by considering the change of volume fractions and grain size of both phases varying with process variables and then implemented into the user-defined subroutine of FEM analysis. In order to demonstrate the reliability of the model, the volume fraction and grain size of primary 𝛼 phase during the hot backward extrusion process of Ti-6Al-4V alloy were simulated. The simulation results were compared with the experimental ones. Jong-Taek Yeom, Jeoung Han Kim, Jae-Keun Hong, Nho-Kwang Park, and Chong Soo Lee Copyright © 2012 Jong-Taek Yeom et al. All rights reserved. Sun, 29 Jan 2012 15:14:26 +0000 http://www.hindawi.com/journals/jm/2012/674573/ Plastic instability is reported in hexagonal close-packed (HCP) LA41 magnesium alloy during tensile tests. Serration amplitude associated with plastic instability is measured to increase with increasing strain and decrease with increasing strain rate. The model of dynamic strain aging (DSA) is proposed to be the controlling mechanism. Moreover, it is reported that annealing could reduce the flow instability, which has potential practical applications. C. Wang, Y. B. Xu, and E. H. Han Copyright © 2012 C. Wang et al. All rights reserved. Wed, 18 Jan 2012 08:28:29 +0000 http://www.hindawi.com/journals/jm/2012/308568/ A Re-rich phase (up to 85.40% wt.Re) was occasionally found in a single crystal superalloy during thermal exposure. Interestingly, this phase is located in front of the dendrite periphery in the interdendritic region, while the Re is segregated in the dendrite core. Formation of this phase was suggested to relate to the unusual accumulation of the Re resulting from the uneven diffusion process of Re. Appearance of this phase may imply the preference of forming Re-Re atomic bond in the superalloys. Kuiyu Cheng, ChangYong Jo, DooHyun Kim, Tao Jin, and Zhuangqi Hu Copyright © 2012 Kuiyu Cheng et al. All rights reserved. Wed, 16 Nov 2011 16:04:15 +0000 http://www.hindawi.com/journals/jm/2011/639283/ A new modified austenitic stainless steel has been developed through partial replacement of nickel by nitrogen. Nitrogen stainless steel was produced in 10 kg induction furnace under nitrogen pressure, while reference one, AISI 316 steel grade, was produced in open-induction furnace. Both were cast and hot forged, and the total nitrogen was determined. Furthermore, the produced forged steels were subjected to solution treatment at different temperatures. The microstructure of produced stainless steels was observed. The X-ray diffractmeter and Mossbauer effect spectroscopy were used to follow the phase change in reference and modified steels after different heat treatment temperatures. The influence of grain-size, soluble, and insoluble nitrogen on tensile strength and hardness was investigated. The major phase in the modified steel has a fcc structure similar to the reference one, but with finer grains and more expanded lattice. The yield strength and hardness of the nitrogen-modified stainless steel are higher than the reference steel. On the other hand, the increase of nitrogen content deteriorates the steel ductility. A. Ahmed, S. N. Ghali, M. Eissa, and S. A. El Badry Copyright © 2011 A. Ahmed et al. All rights reserved. Sun, 16 Oct 2011 15:27:32 +0000 http://www.hindawi.com/journals/jm/2011/954170/ Iron-technetium alloys are of relevance to the development of waste forms for disposition of radioactive technetium-99 obtained from spent nuclear fuel. Corrosion of candidate waste forms is a function of the local cohesive energy (𝐸loc) of surface atoms. A theoretical model for calculating 𝐸loc is developed. Density functional theory was used to construct a modified embedded atom (MEAM) potential for iron-technetium. Materials properties determined for the iron-technetium system were in good agreement with the literature. To explore the relationship between local structure and corrosion, MEAM simulations were performed on representative iron-technetium alloys and intermetallics. Technetium-rich phases have lower 𝐸loc, suggesting that these phases will be more noble than iron-rich ones. Quantitative estimates of 𝐸loc based on numbers of nearest neighbors alone can lead to errors up to 0.5 eV. Consequently, atomistic corrosion simulations for alloy systems should utilize physics-based models that consider not only neighbor counts, but also local compositions and atomic arrangements. Christopher D. Taylor Copyright © 2011 Christopher D. Taylor. All rights reserved. Sun, 21 Aug 2011 10:14:27 +0000 http://www.hindawi.com/journals/jm/2011/959643/ A study was carried out on aging behaviour of a 6082 alloy processed by two different severe plastic deformation techniques: ECAP and asymmetric rolling. Both techniques were able to generate an ultrafine-grained structure in samples processed at room temperature. It was stated that severe straining promotes marked changes in the postdeformation aging kinetics. The peaks of β′′/β′ transition phases were anticipated and of progressively reduced intensity over the coarse grained alloy. A further peak accounting for onset of recrystallization also appeared in the most severely deformed samples. Full consistency in peak shape and position was found when comparing materials processed by ECAP and asymmetric rolling. Isothermal aging treatments performed at 180°C revealed that in the severely deformed samples, aging became so fast that the hardness curves continuously decreased due to overwhelming effects of structure restoration. On the contrary, aging at 130°C offers good opportunities for fully exploiting the precipitate hardening effects in the ultrafine-grained alloy. S. Farè, N. Lecis, and M. Vedani Copyright © 2011 S. Farè et al. All rights reserved. Mon, 15 Aug 2011 12:17:53 +0000 http://www.hindawi.com/journals/jm/2011/682191/ The current work investigated the effect of shot peening (SP) on high cycle fatigue (HCF) behavior of the hot-extruded ZK60 magnesium alloy. SP can significantly improve the fatigue life of the ZK60 alloy. After SP at the optimum Almen intensities, the fatigue strength at 107 cycles in the as-extruded (referred to as ZK60) and the T5 aging-treated (referred to as ZK60-T5) alloys increased from 140 and 150 MPa to 180 and 195 MPa, respectively. SP led to a subsurface fatigue crack nucleation in both ZK60 and ZK60-T5 alloys. The mechanism by which the compressive residual stress induced by shot peening results in the improvement of fatigue performance for ZK60 and ZK60-T5 alloys was discussed. Jie Dong, Wencai Liu, Wenjiang Ding, and Jianxin Zou Copyright © 2011 Jie Dong et al. All rights reserved.