Journal of Welding Science

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Dissimilar joint with good quality and mechanical properties is one of the major problems the industries. One of the most commonly used methods to solve this problem is friction stir welding process. In this paper two different tool pin with simple cylindrical and screwed profile were used to finding optimization of friction stir welding parameters to reach best mixing flow, composite structure and maximum tensile strength in dissimilar joint between AA6065 aluminum alloy and pure copper. In this research 1130 rpm tool rotation, 24, 40 and 65 mm/min travelling speed, 0.3 mm plunge depth and 3o tool tilt angle were carried out. The results shows that internal material flow that produced with screw pin was better than simple cylindrical in constant process parameters. According to the results, at lower tool travelling speed the strength of joint increases. The tensile test results revealed the maximum strength of joint of screw pin was 345MPa with 2.6mm elongation and simple cylindrical pin was 272MPa with 2.2mm elongation which welded with 1130 rpm and 24 mm/min travelling speed.

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The surface of continuous casting moulds with high number of castings may be worn or destructed. As result, an approach for increasing these moulds life is necessary. In this project, the goal is the restoration of the DHP copper sample. In this project, the destruction of the copper sample is done by creation of groove using a CNC machine. The restoration of the sample is done using OAW and filler to fill groove area. In this project, the effect of preheating temperature, filler type and heat treatment of welding area on hardness, microstructure, chemical analyses of welding area and thermal conductivity of the weld are investigated. The preheating temperature range of 300 to 450^oC was selected. The Cu-P and Cu-Ag-P fillers were chosen to fill the groove of the weld area. The scanning electron microscope (SEM), energy dispersive x-ray spectroscopy (EDS), micro hardness tester, optical microscope and thermal conductivity meter were employed for evaluation of the results in this project. The results showed that the increase of preheating temperature creates oxide layers and the decrease of preheating temperature causes the incomplete filling of the welding area. Finally, the preheating temperature of 400 ^oC was a proper choice considering the above mentioned factors. The stress relieving operation to decrease stress and preserve the mechanical properties in the temperature of 250 to 400 ^oC and duration two hours was carried out. The result demonstrated that the selected temperature causes no unwanted decrease on the hardness. It was also found that increasing the annealing duration, decreases the hardness of weld for Cu-P filler for Cu-Ag-P filler increasing the annealing duration, first decreases the weld hardness and then increases the weld hardness. The Cu-P filler was compared with Cu-Ag-P filler. The results showed that the Cu-Ag-P filler has less hardness (around 10 percent) than the filler without silver. On the other hand, the thermal conductivity of the Cu-Ag-P filler was around 10 percent more than the thermal conductivity of the Cu-P. It is obvious that the selection of the filler type depends on the type of base metal and its geometry. The results showed that the segregation in the Cu-P filler with 7.2 percent phosphorous, because of the proximity of the weld structure to the eutectic point, has slightly happened; while, the selection of the Cu-Ag-P filler with 6 percent silver caused severe segregation of silver to 90 percent silver at the center of weld at the non-dendrite area

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The aim of this study is to investigate the effect of rotary frictional welding process variables on microstructure, mechanical and physical properties of copper-aluminum dual-tube pipes. For this purpose, using a thermosetting friction welding machine, a copper pipe (99.44% purity) with a similar diameter aluminum tube (1050), was welded in three different conditions with different friction pressures and forging, and then by metallographic, hardening and microstructural testing it placed. The results of this study showed that with increasing friction pressure from 10 and 15 Bar respectively, in the interconnected phase, fuzzy interclass metal samples were created and caused a great loss in the deformation percentage and tensile strength of the interconnected sample. Also, with the reduction of frictional pressure and the removal of forging pressures down to 5 Bar, there is no proper bond between the two samples and formed in the interface between porosity and cracking. The most suitable result for the microstructure, mechanical and physical properties of the samples is in tubes with an outside diameter of 15 mm and an inner diameter of 10 mm, for samples having a friction pressure of about 10 Bar and a forge pressure of 15 Bar. The presence of intermetallic Al-Cu phases such as CuAl₂, due to higher electrical resistance and ceramic nature, increases the electrical resistance of the joint and, on the other hand, the presence of cracks and pores has reduced the flow rate and eventually increased electrical resistance of the samples

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In this paper, the experimental investigation of formability of friction stir welded ultra-thin sheets of IF steel is investigated experimentally. First, the sheets are joined by friction stir welding process based on the tests determined according to the Taguchi design of experiments. The investigated parameters in the welding process are as tool rotational and traverse speeds. Then, the tailor welded blanks are formed based on dome height test up to the defect stage and the dome height is measured for each test. Therefore, the effects of friction stir welding process parameters on formability of friction stir welded ultra-thin sheets of IF steel are evaluated. The results show that by increasing the rotational speed, the dome height in forming process decreases, while with increasing the traverse speed, the formability of tailor welded blanks by friction stir welding process improves.  Also, the results of optimization based on signal to noise ratio method show that the tool rotational speed has the greatest effect on the dome height of tailor welded blank. 
 

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In this research, the effect of nickel powder as an interlayer and the tool penetration depth on the microstructure and mechanical properties of lap joints between aluminum 1050 (top sheet) and pure copper (bottom sheet), both with a thickness of 2 mm, was investigated. Nickel powder was added through a machined groove with a width and depth of 1 mm at the base of the aluminum sheet. Friction stir lap welding was performed using a hot work steel tool with a shoulder diameter of 16 mm, a pin diameter of 4 mm, a pin height of 2.1 mm, a rotational speed of 950 rpm, a feed rate of 85 mm/min, a tool tilt angle of 2°, and varying tool penetration depths of 0, 0.05, and 0.1 mm. The results revealed that in the sample with a 0 mm penetration depth, due to insufficient heat generation, defects such as tunnel voids were formed. Increasing the penetration depth to 0.05 mm resulted in the formation of uniform and thin intermetallic layers, including Al3Ni2, Al7Cu4Ni, and Cu_3.8Ni at the interface, which enhanced joint quality and increased tensile strength to 185.2 MPa with a fracture strain of 8.7%. In the sample with a 0.1 mm penetration depth, thicker and less uniform intermetallic layers were formed, which, despite locally increasing hardness, led to a decrease in tensile strength and fracture strain to 136.6 MPa and 6.7%, respectively. This study demonstrates that under the conditions of this research, a tool penetration depth of 0.05 mm provides the optimal conditions for FSLW of aluminum-copper alloys using nickel powder.

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In this research, copper/silver-silicon carbide Cu-Ag-SiC composite was prepared by the friction stir processing (FSP). For this purpose, nanometer and micrometer SiC particles were used as reinforcing particles. In order to evaluate the microstructural properties, X-ray diffraction (XRD) analysis, scanning electron microscope and optical microscope were employed. Evaluation of mechanical properties through microhardness measurement, tensile test and pin on disc test were utilized to evaluate the wear behavior of the composite. The results of X-ray analysis revealed the presence of two phases of CuAg solid solution along with SiC particles, which indicated the formation of Cu-Ag-SiC composite. The addition of nano-particles led to a significant decrease in the intensity of peaks compared to micro-particles. This indicated a decrease in the grain size of the CuAg matrix. Using the FSP in the presence of reinforcing particles and without it led to a decrease in the crystal size and average grain size compared to the sample without FSP. So that the grain size of the sample without FSP and the FSPed sample without reinforcing particles and with nano-reinforcing particles were found to be about 46.3, 19.2 and 3.6 µm, respectively. The wear mechanism in the sample before FSP was adhesive wear due to its soft nature of the matrix, and after FSP in the sample without reinforcing particles, the adhesive wear decreased and due to the addition of silicon carbide micro and nano- particles reinforcement, the wear mechanism in entirely altered to abrasive wear. Overall, it can be stated that the addition of silicon carbide nanoparticles by FSP leads to the fabrication of  Cu-Ag-SiC composite with high mechanical properties.

 

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In this research, the mechanical properties and microstructure of L316 grade stainless steel sheets welded using the resistance spot welding method with a copper interlayer were investigated. In this regard, two types Connection were considered: one without the interlayer and the other with the copper interlayer, connected at different currents. To select the optimal current for both types of connections, tensile tests were initially conducted. Following that, microstructural examinations, microhardness tests, elemental evaluations, and failure mode analyses were performed on the optimized samples. according to the results obtained, increasing the electric current raised the input heat in the weld pool to an appropriate level, improving the microstructural and mechanical properties of the weld region. Additionally, due to the optimal electric current in both samples "with and without" the interlayer, both samples experienced interfacial failure, indicating high strength at their joint and weld points. Changes in chemical composition across different weld areas were minimal, and element distribution was reported to be uniform throughout all regions. The highest hardness was observed from the base metal towards the center of the weld in the order of weld area > base metal > heat-affected zone, which corresponded with results from microstructural examinations.
 

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Nowadays, to achieve the simultaneous properties of multiple alloys in important applications such as automotive and aerospace, the use of surface coating methods is common. Coating through welding (cladding) is one of the widely used methods for surface modification of metal parts and sheets in the industry. Low-alloy steel AH36 is one of the steels used in shipbuilding, known for its toughness and good corrosion resistance, gaining significant recognition among other steels used in this industry. In this research, to improve the corrosion properties of this steel, the cladding process was performed using Gas Tungsten Arc Welding (GTAW) with copper/nickel filler wire. Two samples from coated and uncoated sections, termed base metal and weld metal, were prepared and subjected to microstructural and corrosion investigations. The results indicated an increase in grain size in the heat-affected zone of the weld metal sample, leading to a reduction in mechanical properties. The pitting potential for both base and weld metals was reported as -1.7 V and -0.5 V, respectively, indicating a greater capability of the weld metal for pitting repair in case of stable pit formation. The presence of only a single semicircle in the Nyquist plot indicates a single-loop equivalent circuit and confirms the absence of a passive layer. Additionally, resistance to pitting and charge transfer resistance was reported to be higher in the base metal compared to the weld metal