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 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.