Journal of Welding Science

In this study, we employed the active TIG method with ultrasonic vibration (UV) for welding 316L steel. Throughout the active tungsten inert gas (A-TIG) welding process, a high-frequency ultrasonic generator produced high-intensity acoustic waves at an optimal frequency of 20.3 kHz and a vibration amplitude of 8 micrometers. These waves were directed into the molten weld pool, covered by SiO2 nanoparticles serving as an activating flux. The effect of UV and nanoparticles on weld geometry and weld microstructure was analyzed and compared with conventional TIG welding proces. The results indicated that the use of nanopowder not only increased weld penetration by approximately 17.5% but also reduced the Weld Bead Width (WBW) by 28% compared to Conventional TIG. These values increased by 25% and decreased by 35%, respectively, in the presence of ultrasonic waves. Additionally, the introduction of nanomaterials into the molten pool led to finer grains. The ultrasonic waves played a crucial role in ensuring the uniform distribution of these nanomaterials in the melt, ultimately resulting in an enhanced microstructure of the weld.

In this research, dissimilar joining of biodegradable AZ31 alloy to Ti-6Al-4V titanium alloy by rotary friction welding method was investigated with aim of preparation of pin or screw for orthopedic applications. optical and scanning electron microscope (sem) were used to investigate the microstructure, x-ray diffraction was conducted for phase analysis, torsion and micro-hardness tests were carried out to investigate mechanical properties, and polarization and electrochemical impedance spectroscopy were employed to evaluate corrosion resistance. in the welding procedure, rotational speed of 1100, 1200 and 1300 rpm and friction time of 2 and 4 seconds were considered as variable parameters, and two parameters of friction pressure and forge pressure were considered as constant parameters at 50 and 40 MPa, respectively. The microstructure of the joint zone showed that there is no deformation in the titanium alloy side. However, in the magnesium side, the greatest amount of deformation occurred with the distance from the joint line, where weld center zone (CZ), dynamic recrystallization zone (DRX), thermomechanical affected zone (TMAZ) and partial deformation zone (PDZ) are detected. The formation of intermetallic phases such as Mg2AlZn, Ti3Al and also the refining the grains size is the main reason for increasing the hardness of the magnesium side near the joint line up to 150 HV. The results of the torsion test showed that the welded sample has the highest shear strength of 81.51 MPa and also the highest corrosion resistance among other samples at a rotation speed of 1200 rpm and a friction time of 4 seconds.

In this study the effect of rotational speed and tool angle parameters on the microstructure and mechanical properties of the AZ91/CP-Ti joint was investigated, for this reason the sheets with 4 x 26 x 100 mm dimensions were prepared and joint by FSW with different rotational speed (800, 1200 and 2500 rpm) and the tool angle (0.5, 1 and 3 degrees). After joining, the samples were cut and prepared for study of microstructural and mechanical properties. OM and SEM examination shows that the structure of AZ91/CP-Ti nugget zone includes alpha grains and the microstructure of the mix zone on the AZ91 side includes α-magnesium coaxial grains with Mg17Al12 intermetallic compounds. The results of the tensile test show that the maximum tensile strength value (160 MPa) related to the rotation speed of 2500 rpm and the tool angle of 1 degree. It was also determined that the rotation speed of 800 rpm was not suitable for joining of AZ91/CP-Ti. On the other hand, it was observed that by increasing the  tool angle the work piece, initially leads to an increases the strength from 141 MPa to 160 MPa and then decreases to 132 MPa. the results of the Vickers hardness test show that the average of the nugget zone hardness was to 173, which is higher than the hardness of AZ91 alloy (61 Vickers) and near to the hardness of CP-Ti (167 Vickers).

In this research, the optimization of the artificial neural network (ANN) capability for predecting the tensile strength and elongation of friction stir welded Al-5083 (FS-welded Al-5083) was carried out. The effective parameters of ANN, such as the number of layers, number of neurons in hidden layers, transfer function between layers, the learning algorithm and etc. were investigated and the efficient neural network was determined to predict the tensile properties of FS-welded Al-5083. The investigations revealed that the perceptron neural network with two hidden layers and 17 neurons numbers, Lunberg-Marquardt training algorithm and Logsig transfer function for the intermediate layers and Tansig transformation function for the output layer is the most optimized neural network for the prediction. The optimized network has an optimal structure based on the minimum value of the mean square error of 0.05, the maximum total correlation coefficient of 0.93 and the line regression with an angle of 45 degrees between the actual and estimated values. Therefore, this network has a good performance for training, generalizing and estimating of tensile strength and elongation of FS-welded Al-5083.

High entropy alloys are especially suitable for use as filler metals in brazing due to their excellent properties. in the present study, three powders with the composition of CoxCrxCuxFexMnxNix (X atomic percentage of the element) were designed using the criteria of these alloys as well as jmatpro software. in the next step, using mechanical alloying, filler nano powder was synthesized and characterized by X-RAY analysis (XRD) test and the effect of filler composition on the thermal behavior of the alloy was studied. then the filler was used in Inconel 600 super alloy brazing, the single-phase solidification behavior and the absence of boron and silicon in the high entropy filler led to the creation of a continuous microstructure without eutectic components or brittle phases in the brazing interface. thus, the shear strength test was performed and 545 MPa  was the highest shear strength obtained among the three filler compounds. in brazing conventional filler metal, incomplete isothermal solidification and subsequent thermal solidification of the residual liquid results in large grains of chromium-rich boride phase distributed throughout the microstructure. not using compounds that lower the melting point in the filler for the purpose of joining the nickel-based superalloy is considered an important step in reducing the subsequent brazing processes.

In this research, the effect of temperature and time parameters are investigated on the microstructure and mechanical properties of  dissimilar brazing of 17-4 PH stainless steel and Ti-6Al-4V alloy with BNi-2 filler metal. The microstructure of the joint is evaluated with optical and scanning electron microscopes and the mechanical properties of the joint are also evaluated with tensile-shear and microhardness tests. It can be seen that at a constant temperature of 1050°C, increasing the time from 15 to 30 minutes decreases the shear strength from 34.66 to 29.39 MPa. Formation of brittle intermetallic compounds like NiTi2 and FeTi2 increase strength and promote brittle fracture.At a fixed time of 15 minutes, increasing the temperature from 1050 to 1100 °C causes the strength to increase from 34.66 to 38.46 MPa. Also, the increase in temperature and time increases the ISZ thickness formed in the joints on the side of the filler metal - Ti-6Al-4V from 41.40 to 81.48 microns. The increase in temperature and time also causes more diffusion of boron into the SS-filler joint, which forms various boron compounds and widens this region.

In this study, mechanical properties of the transient liquid phase (TLP) bonds between Hastelloy X to Ni3Al IMC at temperature range of 800 - 900 °C were investigated. The microstructure of the joints was examined by optical and scanning electron microscopy. Also, high temperature XRD (HTXRD) analysis was utilized to investigate the phase changes at different temperatures of half-joints. According to microscopic observations, the joint cross-section consisted of three regions including diffusion affected zone (DAZ), isothermal solidification zone (ISZ), and Athermal solidification zone (ASZ), which increasing temperature and time result in ISZ consisting of nickel-rich solid solution developed across the microstructure. The optimum joint bonding strength was achieved for the sample treated at 1100 °C – 180 min equal to 355 ± 4.5 MPa. The ultimate tensile strength reached 36.5 ± 1 and 20.5 ± 1 MPa at temperatures of 800 °C and 900 °C, respectively. Fracture occurred on the side of the IMC substrates at both test temperatures due to the presence of shrinkage porosity during the solidification stage of IMC and crystal lattice parameters mismatch with the matrix.

316 steel is used in transportation, space, and chemical equipment. This steel is in demand in these industries due to its durability. It is used to increase the lifespan and renovate equipment. The research explores the impact of laser energy density on st6 cladding. It specifically focuses on the microstructure and geometric characteristics of the cladding. The cladding is applied on 316 steel. The experiment was designed with energy density changes from 40 to 116 J/mm and powder rate changes between 12 and 20 g/min. Optical and electron microscopic images were used to evaluate the samples. The results indicated that the dendritic arms grew larger with increased energy density. The dimensions increased from 1.5 to approximately 3. In other words, the speed of cooling is doubled. Increasing energy density from 40 to 75 J/mm reduced cobalt to chromium ratio from 2 to 0.7. It also decreased cobalt to iron ratio from 35 to 3. The changes emphasize how energy density affects microstructure and phase transformations.

In this study, the effects of friction stir welding (FSW) parameters on the properties of dissimilar joints formed between 5083 aluminum alloys and 316L austenitic stainless steel, with a thickness of 4 mm, are investigated. The tool speed is varied in the range of 16 to 25 mm/min, while the tool rotation speed is maintained at a constant value of 250 rpm. To examine the microstructure of different weld regions, both optical and scanning electron microscopes are employed. To assess the mechanical properties, hardness and tensile tests are conducted. The results shows the formation of a composite region characterized by steel reinforcement particles dispersed within an aluminum matrix. At the steel-aluminum interface, a single layer of discontinuous intermetallic composition with a thickness of approximately 2 micrometers is observed. Notably, when the rotation speed is set to 250 rpm and the tool speed is 16 mm/min, a tensile strength of 298 MPa and ductility of 26% (93% of the tensile strength and 50% of the ductility of the 5083 aluminum alloy) are achieved.

Society's great and growing demand for buildings and structures has created the need to apply new construction methods to shorten construction times, make buildings lighter, extend their useful life, and make them more earthquake-proof. In the long term, the new methods will lead to structural optimization, increased building performance, and the achievement of optimal operating conditions. New technologies are meeting society's increasing need for special structures more than ever. Additive manufacturing is based on gas metal arc welding as one of the fastest and most cost-effective manufacturing methods for primary metal structures. For this purpose, the three parameters voltage, wire feed speed, and welding speed were considered initial parameters affecting the width and height of the welding flux. To investigate the effects of the process,

16 experiments with input parameters were evaluated. The width and height of the sweat pollen were determined by experimental investigations. Subsequently, the resulting welding geometry is modeled using three numerical modeling methods, including intensive learning machines, relevence vector machine, and fuzzy logic. The comparison between the experimental data and the results of the three generated models shows that fuzzy logic comes closest to the experimental data of the welding geometry of the modeling methods. For example, the test data of the generative fuzzy model resulted in an average error for height and width of 0.667 and 0.5477, respectively, and a root mean square error for height and width of 0.0046 and 0.3, respectively, which expresses the generalization ability and reliability compared to other modeling methods in this process. Finally, a metal pattern of a special structure was produced based on arc and wire additive manufacturing based gas metal arc welding.

In this study, the microstructure and mechanical properties of dissimilar resistance spot welding of AISI 430 steel and S500 MC steel were investigated. To carry out this research, Taguchi's L9 array was used to determine the number of samples and determine the range of variables of each sample, and after welding the samples and performing the shear tensile test, the sample with the highest tensile shear strength (13740 N) and the highest amount of fracture energy (102160 Joules), was considered as the best example; Also, the variables of this sample, i.e., welding current of 12 kW, welding time of 12 cycles, and electrode force of 3 kN, had the highest signal-to-noise values, and these values were chosen among the best range of variables among the proposed variables. Then, a microhardness test was performed on the welded sample with the above variables, and microstructural studies were performed by optical microscope and scanning electron microscope. The hardness of the weld zone was observed to be about 400 Vickers, and the microstructure of the weld metal consisted of ferrite, martensite, and Widmannstatten ferrite.

This research studied the effect of two-stage over aging treatment on the pitting corrosion behavior and microstructure of the weld metals in the 17-4 precipitation hardening stainless steel. For this purpose, this steel was subjected to solution annealing heat treatment at 1035°C for one hour before welding. Then gas tungsten arc welding (GTAW) was performed using ER630 similar filler metal. Subsequently, a section of the weldment was subjected to two-stage over aging treatment. The microstructure and corrosion resistance of the weld zone after the two-stage over aging treatment were investigated and compared with the weld zone behavior in the as-weld condition. Microstructural studies showed that the two-stage over aging treatment of the weld zone led to the tempering of the martensitic, the formation of more reversed austenite, and the formation of α-ferrite. The volume fraction of austenite in the as-weld condition was approximately %7 and increased to about %30 after two-stage over aging treatment, a four-fold increase. The pitting potential (EPit) of weld metal was -18.15 mv in the as-weld condition and reached 122.54 mv after two-stage over aging treatment, which also signifies an improvement in pitting resistance. The two-stage over aging treatment also reduced the potential differences between the different parts of welding zones reducing the galvanic corrosion occurrence. The assessment of mechanical properties through impact test revealed that impact resistance after

This study aimed to investigate the effect of diffusion welding parameters on the microstructural characteristics and mechanical properties of the dissimilar joint between AISI 418 stainless steel and Inconel 738 superalloy using Ni interlayer with a thickness of 50 µm. The experiments were performed in a vacuum furnace at three temperatures of 1000, 1050 and 1150 °C for 45, 60, 75 and 90 min under the pressure of 5 MPa.The results show that voids and non-bonded areas are seen in the samples that were bonded at a lower temperature (1000 °C). By increasing the joining temperature from 1000 °C to 1050 °C, all micro discontinuities have disappeared, which shows that the microplastic deformation of roughness has improved. Then, by increasing the temperature to 1150 °C,non-bonded areas are observed in the joint due to the reduction of pressure on the contact surfaces. When pure nickel is used as an interlayer, intermetallic compounds of
γ' [Ni3(Al, Ti)] are formed in the γ matrix phase on the side of Inconel 738 superalloy while compounds of FeNi3 and γ (γFe, Ni) are formed on the side of AISI 418 stainless steel. According to the results of line scan analysis, the slope and penetration of elements in Inconel 738 superalloy is lower than AISI 418 stainless steel , which indicates less penetration in Inconel 738 superalloy. In the sample welded at the temperature of 1050 °C and the time of  90 Min, the penetration value of the nickel interlayer in AISI 418 stainless steel  and Inconel 738 superalloy was 40 µm and 35 µm, respectively. By comparing the maximum hardness, it can be concluded that the joint at the temperature of 1050 °C and the time of 90 Min has a lower maximum hardness than other samples. Therefore, it has better joint characteristics than other samples in terms of intermetallic compounds. The highest value of shear strength was obtained at the temperature of 1050 °C and the time of 90 Min, which is equal to 270 MPa.