Sharif Digital Repository

Ag and Ni are immiscible, mainly due to their large lattice mismatch. This paper reports on their nanoscale formation of solid solution at room temperature by simple reduction reactions which lead to the amorphous Ag-Ni alloy nanoparticles (ANPs) with mono-disperse distribution. Microscopic and spectroscopic studies confirmed dependence of the alloy composition on size of nanoparticles. In the presence of different ligands such as sodium citrate, polyvinyl alcohol and potassium carbonate a mixture of silver oxide and Ag-Ni ANPs was achieved. Stoichiometry of the Ag-Ni ANPs was also found to be strongly dependent on ligands of the reduction reaction and further study shows without any ligand... 

The non-isothermal aging behaviour of a newly developed Al–Zn–Mg–Cu alloy containing 17 wt-% Zn was investigated. Hardness and shear punch tests demonstrated that during non-isothermal aging, the mechanical properties of the alloy first increased and then decreased. The best properties were obtained in a sample which was non-isothermally aged upto 250°C with heating rate of 20°C min−1, due to the presence of η′/η (MgZn2) phases. This was confirmed by differential scanning calorimetery. After homogenisation, residual eutectic phases remained at triple junctions or in a spherical form. During aging, these phases transformed into rodlike S (Al2CuMg)-phase at 400°C, with sizes ranging from 50 to... 

The non-isothermal aging behaviour of a newly developed Al–Zn–Mg–Cu alloy containing 17 wt-% Zn was investigated. Hardness and shear punch tests demonstrated that during non-isothermal aging, the mechanical properties of the alloy first increased and then decreased. The best properties were obtained in a sample which was non-isothermally aged upto 250°C with heating rate of 20°C min−1, due to the presence of η′/η (MgZn2) phases. This was confirmed by differential scanning calorimetery. After homogenisation, residual eutectic phases remained at triple junctions or in a spherical form. During aging, these phases transformed into rodlike S (Al2CuMg)-phase at 400°C, with sizes ranging from 50 to... 

A severe plastic deformation is widely used to improve the mechanical properties of non-heat-treatable alloys. Thus, the investigation and modeling of microstructural evolutions of materials during large straining are of great importance. In this research, substructural evolutions of four different kinds of Al alloys namely Al-1Mn, Al-1Mg, Al-2.77Mg and Al-5Mg, have been studied using a dislocation based model and the mechanical properties of these alloys have been compared considering all microstructural parameters such as dislocation density, subgrain size, cell wall misorientation and the effect of alloying element. As a result, a simplified general equation has been expressed in order to... 

During the recent years, some Mg based alloys have extensively been considered as a new generation of degradable and absorbable bio-medical materials. In this work, the Mg–2Zn–1Gd–1Ca (wt%) alloy as a new metallic bio-material was produced by the casting process followed by the heat treatment. The samples of the alloy were solution treated at temperatures of 500, 550, and 600 °C and then quench aged at temperatures of 125, 150, and 175 °C. The results of SEM-EDS examinations indicated that the alloy microstructure consists of α-Mg matrix and the Ca2Mg6Zn3 and Mg3Gd2Zn3 secondary phases. With regard to the results of Vickers hardness test, the temperatures of 500 °C and 150 °C were selected... 

Ni-Fe and the Ni-Fe-Cr-Mo alloy films were electrodeposited from a chloride solution containing complexing compounds on ITO/glass substrates. AFM studies revealed a spherical structure for the alloy films with roughnesses from 10 up to 50 nm. The Ni-Fe-Cr-Mo alloy films were found to have a fine-grain structure. The quaternary alloy compounds containing up to 4% Cr and 2% Mo showed higher resistivity and little decrease in magnetoresistance (MR) relative to the Ni80Fe20 alloy compound. The MR of the quaternary alloy compounds was decreased for higher Cr and Mo contents. Moreover, the anisotropy (AMR) was also decreased by the addition of Cr and Mo to Permalloy films. Auger studies indicated... 

The anisotropic (Nd,MM)2(Fe,Co,Ni)14B-type magnets were produced using the binary alloy sintering method (MM denotes a Misch-metal). The composition of the master alloy was close to stoichiometric Nd2Fe14B compound, while that of the sintering aid was MM38.2Co46.4Ni15.4. The microstructures of sintered magnets were investigated using a scanning electron microscope (SEM) equipped with an energy dispersive X-ray detector (EDX). X-ray diffractometry (XRD) was also employed for phase analysis. The optimum magnetic properties were obtained for a composition of Nd11.9MM2.9Fe73.9Co3.3Ni1.1B6.9 made of 90 wt.% master alloy and 10 wt.% sintering aid. The two main phases, i.e. the (RE)2(TM)14B phase... 

Biodegradable magnesium (Mg) alloys exhibit great potential for use as temporary structures in tissue engineering applications. Such degradable implants require no secondary surgery for their removal. In addition, their comparable mechanical properties with the human bone, together with excellent biocompatibility, make them a suitable candidate for fracture treatments. Nevertheless, some challenges remain. Fast degradation of the Mg-based alloys in physiological environments leads to a loss of the mechanical support that is needed for complete tissue healing and also to the accumulation of hydrogen gas bubbles at the interface of the implant and tissue. Among different methods used to... 

The effects of Sr additions, heat treatment (T4 and T6), and multi-directional forging on the microstructural evolution, mechanical properties and biodegradability of Mg-4Zn-xSr alloys were investigated. Corrosion behavior of the alloys was evaluated by the polarization and hydrogen evolution tests. Shear punch and hardness tests were employed to determine the mechanical properties. It was found that mechanical properties and corrosion resistance of the as-cast Mg-4Zn alloy increased by 0.3 wt% Sr addition. However, further increasing the Sr content not only did not improve the mechanical strength, but also had detrimental effects on the corrosion resistance, due to the increased size and... 

The hot ductility of Fe-29Ni-17Co alloy was studied in both cast and wrought conditions by hot tensile tests over temperature range of 900-1250°C and at strain rates of 0.001-1s-1. Over the studied temperature range, the wrought alloy represented higher elongation and reduction in area as compared to the cast alloy. Dynamic recrystallization was found responsible for the higher hot ductility of the wrought alloy and the improvement of hot ductility of the cast alloy at high temperatures. At temperature range of 1000-1150°C the wrought alloy exhibited a hot ductility drop while a similar trough was not observed in case of the cast alloy. It was also found that at temperatures of 1150-1250°C... 

Concurrent precipitation in an age hardenable aluminum alloy determines recrystallization behavior especially grains structure and recrystallization texture during continuous heating. In this study, to investigate the effect of concurrent precipitation on the recrystallization texture and grains structure, a solution treated Al-Cu-Mg alloy has been multi-directionally forged at room temperature and continuously heated with different heating rates (800, 1600 and 2500 K·min− 1) up to 450 °C using Gleeble 3800 thermo-mechanical simulator. At lower heating rates (800 K·min− 1), Goss texture component {110} 〈001〉 (Φ1 = 90°/0°, Φ = 90°/45°, Φ2 = 45°/90°) is developed during continuous heating and... 

Cu-1·5Cr alloy was successfully produced by a new method, composed of alloying via melting in a non-protected atmosphere followed by rapid cooling in a water cooled mould. The effects of deformation magnitude during T10 treatment on microstructure, electrical conductivity and hardness of alloy were also investigated. The results showed that cold work before age hardening treatment, especially in the range of 20-40% deformation, provides optimum electrical and mechanical properties, i.e. electrical conductivity of 70-85% International Annealed Copper Standard (IACS) and hardness of 160-180 HB. In addition, the cold work promotes a useful anisotropy in electrical and mechanical properties of... 

Solidification cracking is one the most common types of cracking in the weld of the aluminum alloys. Although some numerical models have been developed for investigation of the solidification cracking, the effect of the grain misorientation on the solidification cracking susceptibility (SCS) of a weld has rarely been considered. This work studies the effect of the angle between the primary arms of the dendrites on the SCS. Hence, a solidification cracking model was developed given the grain misorientation in the convergence condition. The model was investigated for Al-Cu alloys. When the grain boundary energy was considered in the model, there was an increase in the SCS for misorientation... 

In this paper, the rapid synthesis of nanostructured NiTi–Ni3Ti intermetallic alloy from titanium and nickel powders through mechanical alloying followed by microwave-assisted sintering process was investigated. The sintered samples at different temperatures exhibited major phases of NiTi– B2 and Ni3Ti, and minor phases of NiTi–B19′ and Ti2Ni. The density, porosity and microhardness of the sample varied based on the sintering temperature, in which the highest density and microhardness (~750 H V) were obtained at sintering temperature of 1100 °C. Based on the results of this research, the microwave-assisted sintering can be applied to fabricate Ni–Ti alloys with improved mechanical properties... 

Bead-on-plate submerged arc welding was performed on the AISI 4135 heat-treatable low-alloy (HTLA) steel using S2 welding wire and granular Cr-Mo basic flux. The Cr-Mo active flux was produced by the bonded -unfused method. The alloying elements were introduced into the weld metal by active flux. Two methods were introduced for calculating the recovery rate (η) of the alloying elements. Moreover, by defining the slag factor (α) of the process and η of the alloying elements, the amount of a specific element transferred from flux into WM was calculated by the proposed equation. Likewise, microstructure evolutions, inclusions characteristics, longitudinal tensile, indentation, and CVN impact... 

In this paper, the rapid synthesis of nanostructured NiTi–Ni3Ti intermetallic alloy from titanium and nickel powders through mechanical alloying followed by microwave-assisted sintering process was investigated. The sintered samples at different temperatures exhibited major phases of NiTi– B2 and Ni3Ti, and minor phases of NiTi–B19′ and Ti2Ni. The density, porosity and microhardness of the sample varied based on the sintering temperature, in which the highest density and microhardness (~750 H V) were obtained at sintering temperature of 1100 °C. Based on the results of this research, the microwave-assisted sintering can be applied to fabricate Ni–Ti alloys with improved mechanical properties... 

Bead-on-plate submerged arc welding was performed on the AISI 4135 heat-treatable low-alloy (HTLA) steel using S2 welding wire and granular Cr-Mo basic flux. The Cr-Mo active flux was produced by the bonded -unfused method. The alloying elements were introduced into the weld metal by active flux. Two methods were introduced for calculating the recovery rate (η) of the alloying elements. Moreover, by defining the slag factor (α) of the process and η of the alloying elements, the amount of a specific element transferred from flux into WM was calculated by the proposed equation. Likewise, microstructure evolutions, inclusions characteristics, longitudinal tensile, indentation, and CVN impact... 

The development of active, durable, cost-effective, and stable electrocatalysts is an urgent need for various industrial fields including renewable energy systems. The state-of-the-art catalysts suffer from poor water splitting activity in alkaline media due to their sluggish kinetics, high cost, and scarcity on earth to be scaled up. Herein, we present an electrochemical analysis of a nanostructured electrocatalyst based on a face-centered cubic (FCC) copper-rich Cu-Ni-Fe-Cr-Co alloy with a quasi-spherical morphology electrodeposited on a highly porous nickel substrate. Electrochemical studies determine the enhanced electrocatalytic activity toward both hydrogen and oxygen reactions in an... 

This paper addresses the process-microstructure-strength correlation during dissimilar brazing of TiAl alloy to IN738 Ni-based superalloy using Ni–4Si–3.2B filler metal. The solid/liquid reactions, solidification phenomena, and solid-state phenomena are analyzed. The thickness of the athermal solidification zone and reaction layer at different bonding conditions (holding times and temperatures) determined and analyzed using a Larson–Miller parameter (LMP). It was resulted that the shear strength of the joint can be formulated regarding bonding temperature and holding time through using LMP. It was found that the sizes of athermally solidified zone and reaction layer are two key factors... 

The recrystallization behavior of an Al-Cu-Mg alloy is investigated in multi-directionally forged over-aged and solution treated alloys, during non-isothermal annealing. Deformation and non-isothermal annealing are performed with a Gleeble 3800 thermo-mechanical simulator. The hardness measurements show that there is a thermal stability in mechanical properties during non-isothermal annealing up to 250 °C with heating rate of 10 K·min− 1. Differential scanning calorimetry curves of deformed over-aged and solution treated alloys describe the related precipitation phenomena. EBSD maps demonstrate that partially recrystallized and fully recrystallized microstructures appear in deformed...