IRANIAN JOURNAL OF MANUFACTURING ENGINEERING
Year:2019 | Volume:6 | Issue:1 |Papers Count:6

Friction stir processing (FSP) is a surface processing method to modify the microstructure and enhance the mechanical properties of metal surface. In the current research, the work specimen is vibrated normal to processing line during FSP. Transverse and rotation movements of shoulder are accompanied with vibration motion of specimen. This new process is entitled FSVP (friction stir vibration processing). The effects of FSP and FSVP processes on microstructure and mechanical properties of Al5052 alloy matrix composite incorporated SiC nanoparticles are analyzed. The results show that the presence of vibration during FSP leads to the grain size decrease in the stir zone and it enhances the homogeneity of particles distribution. The results indicate that strength and ductility of FS processed specimens are lower than those processed by FSVP. These are related to increased deformation and strain of soft material in the stir zone as vibration is applied which promotes the dynamic recrystallization during FSP. The results also imply that the characteristics of FSV processed specimens improve as vibration frequency enhances.

In this paper, the effect of titanium element on microstructure and mechanical properties of Fe-Ni-C-W powder hardfacing coating was investigated. Electrode coatings were made by a combination of iron, ferro-boron, nickel, ferro-titanium, tungsten and graphite powders. The electrode core was obtained from the E6013 electrode. The results of microstructural analysis showed that the microstructure of the weld metal of specimen 1 included the matrix of needle-like martensitic, residual austenite regions and carbides, while the microstructure of the weld metal of sample 2 consisted of austenite matrix with martensitic and residual austenite regions as well as carbides. The results of the EDS analysis indicated that the carbides consist of titanium carbides and tungsten carbides. There are also some tungsten carbides around titanium carbides. The results of XRD analysis showed that the phases present in the weld metal of samples 1 and 2 were austenite, martensite, titanium carbide, tungsten carbide and titanium oxide. The results of the Vickers microhardness test showed that in the weld metal of sample 1, the average hardness of the austenitic regions is 714 HV and the average hardness of the martensite regions is 804 HV. Also in the weld metal of sample 2, the average hardness of austenite regions is 334 HV and the average hardness of the martensite regions is 565 HV. The results of the Rockwell C hardness test showed that the average hardness of sample 1 weld metal is 42 RC and the average hardness of sample 2 weld metal is 49 RC.

Todays, since using metallic nanoparticles has been developed in various industries, achieving new methods to produce them is considered as an important issue. Comparing to other nanoparticle production methods, the dielectric discharge process has been emphasized due to its low cost and environmental compatibility. In this study, the ultrasonic-assisted electrical discharge process is designed and manufactured in order to produce copper nanoparticles in di-ionized fluid. The different machining parameters effect, as current intensity, pulse on/off time, and the ultrasonic vibrations on the produced particle size, material removal rate, suspensive particle stability in the fluid, and the particle abundance percentage is investigated. Characterizing the produced nanoparticles is done by different methods. Determining the purity of nanoparticles, percentage of abundance and the average particle size in the dielectric fluid and the produced particle size has been done by applying Energy Dispersive Analysis by X-ray (EDAX), Dynamic Light Scattering (DLS) and Field Emission Scanning Electronic Microscope (FESEM) image, respectively. Based on the results, the produced nanoparticles purity was more than 95%. By using ultrasonic vibration, the nanoparticles stability significantly was increased and the sedimentation time was more than 5 months. Moreover, the average particle size in more than 70% was less than 100 nm.

The aim of this article is to investigate the effect of Equal Channel Angular Pressing (ECAP) intermediate on the mechanical and microstructure properties of pure copper. For this purpose, three molds with internal angles of 65, 75 and 90 degree were designed and made and copper samples were examined for all these molds during 4 passes of extrusion. The results of the investigation of copper microstructure showed that by increasing the number of extrusion passes, the structure of copper in all molds was changed from micrometer to nanometer. The greatest reduction in the microstructure of the copper metal was related to the mold with a 65 degree internal channel angle and the lowest was 90 ° . The hardness changes of the workpiece showed that significant increase compared to the neat sample due to the more applied force and shear strain by the mold body. After the fourth pass extrusion measured hardness at 90, 75 and 65 degrees, where 141, 138 and 131 HB, respectively. The results of the tensile test showed that by decreasing the angle of the mold channel from 90, 75 and 65 degrees, the ultimate tensile strength of the final extruded parts increased by 23, 29 and 31 percent, respectively, relative to the raw material. The fatigue life of the ECAPed sample in the mold with an angle of 65 degrees had a 1700% improvement. ECAPed parts with a 90-and 75-degree angle improved lifetime by 1400 and 1500% times, respectively.

Lost Foam Casting (LFC) is one of the new methods of casting developed in recent years in many industries. This casting method enjoys many advantages competing with traditional casting methods. Take control of process parameters in LFC lead to the production of complex and high-quality specimens. The objective of the present study is the effective parameters optimization in lost foam casting using Taguchi method based on experimental results. At the first stage, the effective casting parameters such as foam density, melting temperature and coating viscosity are selected as optimization design variables. On the second stage required samples are fabricated in three different levels. In addition, the effects of considered parameters are studied on the surface quality, porosity and stiffness of the samples by Taguchi method. The results showed that the lowest porosity, maximum hardness and the best surface quality are determined for the coating viscosity 20 Pa. s, the melting temperature 740° C and foam density 20 kg/m3.

The main purpose of this study is investigation the effects of mechanical and thermal properties on accuracy of finite element model in resistance spot welding of AZ61 Mg alloy. In this study temperature dependent thermo-mechanical properties of AZ61 Magnesium alloy sheets and also thermal and electrical contact conductance (TCC and ECC) have been experimentally determined to use in a coupled electrical-thermalmechanical finite element (FE) model in order to predict distribution of residual stresses and nugget size in resistance spot welding (RSW) process. The thermo-mechanical properties, TCC and ECC have been employed in FE model as: constant, linear and temperature dependent to investigate the effects of these parameters on accuracy of the FE model. In addition, different welding parameters such as welding current, welding time and electrode force have been used in FE model to achieve different nugget size. The results showed that thermal conductivity, electrical resistivity and ECC have significant effect on nugget size and also yield stress and elastic modulus have important influence on distribution of residual stresses. Therefore, the thermal conductivity, electrical resistivity and ECC for prediction of nugget size and also the yield stress and young modulus for prediction of distribution of residual stresses should be assumed to be temperature dependent and linear, respectively. Moreover, remaining thermo-mechanical properties can be taken as constant.