Journal of Welding Science

Unlike conventional welding methods, joining titanium alloys to steels using ultrasonic welding does not result in the formation of brittle intermetallic compounds and high torsion, causing a reduction in the mechanical properties of the joint. Ultrasonic welding of the St12-CP.Ti samples was performed at constant parameters of 7 bars, 2 s and 1 kW and variable parameter of interlayer material (Cu, 70B and Zn). The investigation of samples by OM, SEM, shear-tensile and microhardness tests revealed that Zn and Cu samples had the lowest and highest bond densities, with 42.2 and 80.6 percent, respectively. The bond density and the strength of the sample with greater interlayer deformability have higher values. Due to the high plastic deformation capability of copper, the Cu sample has generated more heat and deformation at the joint interface than in the other samples. As a result, the microstructure underwent recrystallization and grain growth after enduring severe plastic deformation. Also, the highest hardness of the steel side equal to

Wire-arc additive manufacturing (WAAM) is a prominent technique for producing large metallic components due to its high deposition rate. Utilizing austenitic stainless steels in this process not only reduces production costs but also provides greater design freedom. Among these steels, SS310, known as heat-resistant steel in the industry, offers excellent oxidation resistance and high-temperature performance. However, it is highly susceptible to hot cracking during welding and additive manufacturing processes. In this study, the microstructure and mechanical properties of SS310 fabricated using WAAM with Cold Metal Transfer (CMT) and Gas Metal Arc Welding (GMAW) processes were compared. The results revealed that the CMT process, due to its lower heat input, effectively reduces the susceptibility of SS310 to hot cracking compared to the GMAW process. These findings emphasize the importance of selecting an appropriate process to achieve high-quality components and minimize structural defects.

In this study, 1 mm thick austenitic stainless steel 316L sheets were used for experimental testing. The experimental welding process was carried out using a Nd:YAG pulsed laser welding machine, and the welding simulation was performed using the SYSWELD software with a three-dimensional model for thermodynamic and mechanical analysis. The simulation results showed over 90% correlation with the experimental results. Analysis of experimental and numerical data revealed that at a constant voltage of 440 volts, decreasing the welding speed from 2 to 0.5 mm/s increased the overlap rate of pulses from 67% to 93% and the maximum average power density (EPPD) from 5963 to 21831 W/mm². Additionally, increasing the voltage from 440 to 480 volts at a constant speed of 1 mm/s raised the heat input from 114 to 138 J/mm and the weld depth from 0.56 to 0.66 mm. Due to the high cooling rate, the grain size of the weld metal became finer than the base metal (63% reduction in grain size). Two phases, austenite and ferrite, were observed in the weld metal, and the solidification mode was predicted to be FA.With an increase in welding speed from 0.5 mm/s to 2 mm/s at a constant voltage of 440 volts, the maximum tensile residual stress increased from 96 to 260 MPa due to reduced pulse overlap (from 93% to 67%), uneven heat distribution in the part, and the generation of thermal stresses. Furthermore, increasing the welding voltage from 440 to 480 volts at a constant speed of 1 mm/s caused the maximum tensile residual stress to rise from 124 to 152 MPa. The maximum hardness of the weld metal increased from 180 to 215 Vickers as the welding speed rose due to the prevention of carbon diffusion and an increased growth rate. However, with an increase in welding voltage and heat input (from 57 to 69 J/mm), the hardness decreased from 225 to 215 Vickers due to a reduction in thermal gradients and grain growth.

This research looks at how microstructure and mechanical properties change in resistance spot welds of QP980 advanced high-strength steel. It specifically focuses on the effects of zinc coating and how it influences weld nugget formation, mechanical properties, and fracture behavior. The study involved microscopic examinations, mechanical tests, and finite element simulations to determine the thermal history of different weld zones. A key finding was that rapid cooling during the welding process led to the formation of, metastable phases, such as martensite, in both the weld nugget and the heat-affected zone. A finite element model of the welding process was used to simulate heat distribution and analyze the microstructure in various weld regions. This model showed that reaching the peak temperature during four-pulse resistance spot welding is delayed. This delay, along with proper hold times, helps prevent the formation of voids. The simulated thermal history and the rapid heating/cooling conditions effectively predicted the evolution and transformation of the microstructure in different weld areas. It was found that the presence of a zinc coating, and the resulting reduction in electrical contact resistance, delayed the formation of the weld nugget at lower welding currents. However, at higher currents, the primary source of heat generation shifted from contact resistance to bulk resistance within the steel sheet. This led to larger weld nuggets in coated samples compared to uncoated ones. While uncoated samples showed higher weld nugget hardness (512 Vickers) and greater tensile-shear strength (with a maximum load-bearing capacity of 28.1 kN in uncoated samples versus 24 kN in coated samples), coated samples were able to achieve the critical weld nugget size for a change in fracture mode at lower welding currents (9 kA compared to 9.5 kA).

This study investigated the influence of resistance spot welding current intensity on the formation of liquid metal embrittlement (LME) cracks in galvanized advanced QP1180 steel. Galvanized steel sheets with a thickness of 1 mm were welded at currents of 6.5, 7, 7.5, and 8 kA. The results revealed that increasing the current significantly enlarged the weld nugget size, molten volume, electrode indentation, and the likelihood of LME crack formation. Microstructural analysis, elemental distribution, and crack characterization were conducted using optical and electron microscopy. The findings indicated that the weld zone microstructure primarily consisted of martensite, while the non-uniform distribution of zinc along grain boundaries facilitated the initiation and propagation of LME cracks. Cracks were predominantly observed at the periphery of the weld pool indentation and in the electrode-sheet contact area. This study demonstrates that controlling welding current intensity is a key factor in mitigating LME and improving the mechanical properties of joints in galvanized QP1180 steel. Optimizing welding parameters, particularly limiting current intensity, can prevent molten metal-induced cracking and enhance the durability and safety of automotive structures. Hardness profiling revealed peak hardness in the weld zone, followed by a gradual decrease toward the heat-affected zone (HAZ).

In this study, the effects of diffusion-bonding temperature and time on the microstructure and corrosion behavior of Al₀.₅CoCrFeMnTi₀.₅ high-entropy alloy coatings applied on A283 plain carbon steel were investigated. The coatings were produced by diffusion bonding using the spark plasma sintering method, in which high-entropy alloy powders were bonded to the substrate at temperatures of 850, 950, and 1050°C for holding times of 10, 15, and 20 minutes. Microstructural characterization performed by field-emission scanning electron microscopy (FESEM) revealed that increasing the diffusion-bonding temperature and time led to reduced porosity and enhanced coating densification. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests conducted in a 3.5 wt.% NaCl solution demonstrated that increasing the bonding temperature and time resulted in higher charge transfer resistance (Rct) and corrosion potential (Ecorr values, along with a decrease in corrosion current density (icorr). The coating produced at 1050°C with a holding time of 20 minutes exhibited the highest corrosion resistance. The improvement in corrosion performance was attributed to the formation of a uniform and adherent oxide film, which effectively inhibited the penetration of corrosive ions into the steel substrate.

In the present study, AISI 1030 cast-steel samples were cladded using duplex stainless-steel wire ER2209 by the Gas Tungsten Arc Welding (GTAW) process under different preheating temperatures and varying numbers of passes. The  degrre of dilution of the clad layers,affected by both  of the preheating temperature and the number of passes—was calculated, and was evaluated its influence on the adhesion and bonding integrity of the ER2209 clad layer on the cast-steel substrate. The results showed that by increasing the number of clad layers led to a lower dilution in the samples. Furthermore, a rise in preheating temperature also contributed to an increase in dilution. Among all conditions, the three-pass cladded sample with a preheating temperature of 100 °C exhibited the highest dilution degree. Bending test results demonstrated that the bending angle increased by the number of clad passes. Macroscopic examination confirmed  that complete interfacial continuity between the clad layer and the base metal. Phase analysis and microstructural observations revealed that the base metal consisted of approximately 80% ferrite and 20% pearlite; the heat-affected zone (HAZ) exhibited a ferrite–transformed pearlite structure with similar volume fractions; and the cladded samples in the final pass presented a duplex austenitic–ferritic structure with 10–20 Wt.% ferrite content. Microhardness test indicated that the two-pass cladded sample  that preheated at 200 °C had the highest hardness value, up to 355 HV.