METALLURGICAL ENGINEERING
Year:2019 | Volume:22 | Issue:2 (74)|Papers Count:7

There are plenty of bone damages due to different reasons these days. In order to heal of damaged area, utilizing of the scaffold is necessary. The main aim of this research is fabrication and investigation of Calcium Phosphate/Gelatin-Starch composite scaffolds. After synthesizing the Calcium Phosphate particles via sol gel route, three different methods were used to manufacture Calcium Phosphate/ Gelatin scaffolds. The method which has the porous structure was selected as the main method for fabricating Calcium Phosphate/ Gelatin-Starch scaffolds. Weight percentage of starch and applying the Gelatin-Glutaraldehyde coating were chosen as two variations. According to mechanical properties results, the sample with 60 weight percentage of Gelatin and 40 weight percentage of Starch has the highest final flexural strength which are 4. 5 and 2. 3 MPa for samples with and without Gelatin-Glutaraldehyde coating respectively. The SEM results show the completely porous structure with interconnected pores on the surface of coated samples and some local pores in internal parts of the scaffolds. According to the result of cell culture, these scaffolds provide surfaces that facilitate the response of stem cells related to attachment, survival, and proliferation.

Solvent extraction process of metals from aqueous solution containing impurities has been the subjects of numerous studies. . In the present work, separation of zinc from solution of filter-cake leaching unit in the presence of Mg impurity was investigated using the D2-ethyl hexyl phosphoric acid (D2EHPA) extractant diluted in kerosene. Different experiments were carried out to evaluate effects of main parameters on recovery and separation of zinc from the sulphate solution. Parameters affecting the extraction process such as pH, D2EHPA concentration, temperature, and organic to aqueous ratio were evaluated. Based on the results obtained at optimal conditions, the pH =2. 5-3, [D2EHPA]=20%(vol/vol) and at 40 ° C, the extraction efficiency of zinc and magnesium ions were 95% and 10%, respectively, while the value Δ pH0. 5(Zn-Mg) factor was obtained more than 5. 1 under the condition of [D2EHPA]= 20%(v/v). Also for the aqueous to the organic phase ratio (A/O) of 1: 1, an optimum zinc separation factor of 5010 was calculated.

Solid-lubricant MoS2 coating has been widely used in many applications, especially space applications in view of its good performance in vacuum. Since the MoS2isvery sensitive to water vapor and oxygen it is not suitable for applications in moist environments. One way to improve the durability of a MoS2 film and also to reduce the deleterious effects of humidity and oxidation on its tribological performance is to co-sputter it with a metal. In this study MoSx/Ti composite coatings were deposited onto AISI 1045 steel substrates by direct-current magnetron sputtering. The Titanium ratio in the coatings was controlled by sputtering the composite targets. The coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and nano-indentation and nano-scratch techniques. The tribological behavior of the coatings were investigated using a pin-on-disc test at room temperature. The results showed that the thickness and the hardness of the coating were 4-6 μ m and 850-1400 HV, respectively. The incorporation of Ti to MoSx coatings resulted in a considerable improvement of coating adhesion and hardness. The optimum doping level for Ti-MoSx coatings to show the best tribological properties, ) with both the lowest friction coefficient and wear rate (was 5 atomic percent. The main wear mechanism of coating was delamination.

Understanding softening mechanisms of wrought aluminum alloy during hot deformation processes is important in order to control microstructure and to predict flow stress accurately in simulation. In this paper, hot compression tests have been done to study the hot deformation behavior of an A5456 aluminum alloy. The effect of temperature, strain and strain rate on flow behavior of the alloy has been studied as well. For this meaning, several cylindrical samples with respectively 10 and 15 mm in diameter and length have been subjected to the test at 350, 400, 450, 500 and 550 ° C, strain rates of 0. 001, 0. 01, 0. 1, 1 s-1 and strain of 0. 7. The samples where then immediately quenched in water in order to study the microstructure. Analysis of the strain – strain curves at different deformation conditions show that the flow stress decreases with increasing the test temperature and decreasing the strain rate. Because of high stacking fault energy of aluminum alloy, the dominant softening mechanism in this alloy is dynamic recovery. From experimental results, the equations governing the hot deformation behavior of the material have been determined at peak stress and activation energy of 182 KJ/mol for hot deformation process has been obtained.

Electron Beam Welding (EBW) is a high-efficiency, high-precision welding method that its application is increasing rapidly in various industries, including car manufacturing, aviation and aerospace. The simulation of the electron beam welding process with the aim of predicting the residual stress in the work piece and analyzing the temperature and stress profiles during the welding process has always been of interest to the researchers for the purpose of welding engineering and prediction of optimal conditions. In this research, the Finite Element Method (FEM) model of electron beam welding was prepared in 3D and loaded on the Abaqus software. This model includes thermal and mechanical interaction, and metallurgical phenomena. The thermal analysis is unilaterally coupled with mechanical analysis. The heat source that is used is a combined heat source that is attached to Abaqus using the subroutine and the Fortran coding. Welding is in a vacuum environment and the thermal dissipation due to thermal conductivity and radiation is applied in different parts as boundary conditions on the model. The workpiece is made of Ti– 6Al– 4V alloy and has thermal and mechanical properties which are defined dependent on temperature. The temperature variations during welding and the residual stress of the base metal which is obtained from the numerical simulation are comparable to the results recorded in the practical studies and an acceptable adaptation was made that shows the accuracy of the combined heat source model used in this research for modeling of electron beam welding.

Dissimilar joining of Al5083 to MgAZ31 was performed through friction stir welding (FSW) and diffusion bonding (DB). A constant tool rotation rate of 400 rpm and travel speed of 50 mm/min was used for FSW. The peak temperature of this specimen was raised to maximum of 435° C at the advancing side of the FS weld. Thermal cycle of the FSW specimen showed a distinct plateau at about 430 ° C, lasting for about 8 s. At the travel speed of 50 mm/min, the distance corresponding to 8 s is about7mm, which is the pin diameter. The presence of the temperature plateau indicates that the temperature at eachthermocouple remained constant as the pin passed it. It further indicates that a eutectic reaction probably occurred, and kept the temperature constant as the pin passed by. The weld had anirregular shaped region in the weld center of DB weld and, having a different microstructure and hardness from the two base materials. The irregular shaped region in DB weld, contained a large volume of intermetallic compound Al12Mg17. The present study suggests that constitutional liquation and solid state diffusion at the interface resulted in the intermetallic compound formation in the weld center.

In the last two decades, efforts for increasing Magnesium (Mg) applications and finding solutions for overcoming its limitations have increased. At the same time, production and demand for Mg alloys have also increased significantly in the international markets. In response to the international trends, attention to Mg production and its consumption has also grown in Iran. In the present paper different technologies of Mg production has been briefly introduced and local opportunities in Mg production are summarized and elaborated. Despite the existence of important opportunities in local Mg production, including easy access to low cost and clean energy, raw material and workforce, Mg production features high potential important threats. Different threats to local Mg production including limitation in access to appropriate raw material and access to large working capital are further discussed in this paper. At the end, amongst investigating the history of Mg production, supply and demand in Iran, main structural and metallurgical applications of Mg in local industries are described. Technical and financial feasibility studies indicate that Iran has major advantages in production and consumption of Mg and this industrial sector will experience major growth in the future.