Journal of Advanced Joining Processes最新文献

The keyhole depth is a key measurement characteristic in the laser welding of busbar to battery tabs in battery packs for electric vehicles (EV), as it directly affects the quality of the weld. In this work, experiments are carried out with controlled and adjusted laser power and feed rate parameters to investigate the influence on the keyhole width, keyhole depth and porosities. A 3D numerical model of laser keyhole welding of an aluminum alloy (A1050) has been developed to describe the porosity formation and the keyhole depth variation. A new integration model of the recoil pressure and the rate of evaporation model is implemented which is closer to the natural phenomena as compared to the conventional methods. Additionally, major physical forces are employed including plume formation, upward vapor pressure and multiple reflection in the keyhole. The results show that keyhole depth is lower at higher feed rate, while lower feed rates result in increased keyhole depth. This study reveals that low energy densities result in an unstable keyhole with high spattering, exacerbated by increased laser power. Mitigating incomplete fusion is achieved by elevating laser energy density. The findings emphasize the critical role of keyhole depth in optimizing laser welding processes for applications like busbar-to-battery tab welding.

In this study, different techniques are applied to measure diffusion coefficient D of three cold-rolled Advanced High-Strength Steels (AHSS): CR700Y-980T-DH, CR780Y980T-CH, and DR700Y980T-DP, and their laser-welded counterparts. By thermal desorption analysis (TDA) the hydrogen transport at elevated temperatures is investigated. This method allows the measurement of hydrogen quantities at different trapping sites and enables the determination of activation energies E_a and pre-exponential diffusion coefficients D₀. The analysis is conducted under various temperature regimes using different heating rates $\phi$. Additionally, the corresponding diffusion coefficients for the examined states are determined by electrochemical permeation (ECP) at room temperature. The findings indicate an increase in D after laser welding, with differences in microstructure and material chemistry being identified as the reasons behind this phenomenon. This study demonstrates that the employed method, along with the chosen sample geometries, holds significant potential for enhancing our understanding of hydrogen kinetics in AHSS and the effects of thermal heat treatments, such as laser-welding.

This paper investigates the low-transformation-temperature (LTT) effect in austenitic high alloy stainless steel and its influence on strain evolution of laser beam welded specimen. Due to the local heat input high temperature gradients occur between weld seam and base material, which lead to thermal and transformation induced strains. With targeted alloying in the weld seam the martensitic phase transformation can be shifted to lower temperatures resulting in the so-called Low Transformation Temperature (LTT) effect. This effect uses the volume expansion during the martensitic phase transformation. The delayed volume expansion during martensite phase transformation introduces continuous compressive strains until room temperature is reached and represents a mechanism that can serve to counteract the tensile strains caused by thermal shrinkage. The martensitic microstructure is achieved by dissimilar welding, combining an austenitic stainless steel base material with low alloyed filler wire. With this, the chemical composition of chromium and nickel is diluted, and a martensitic phase transformation occurs. As comparison, similar material combinations of stainless steel base material and conventional welding consumable are performed. In this work, in situ energy-dispersive x-ray diffraction (EDXRD) measurements in the beamline P61A at DESY are performed to investigate the expansion behaviour of martensite based on spectral data. Nine measuring positions are recorded and the strain evolution during welding and cooling of the samples are analysed. It is shown that the martensitic phase transformation changes the strain behaviour and implements compressive strain depending on the distance to the laser spot. It is found that the effect is orientation-dependent and that the highest strain influence is present in welding direction.

This work utilized a gradient method of joining plain carbon steel to stainless steel 316 L and then to Inconel 625 using wire arc additive manufacturing. The research investigated the quality of Functionally Graded Materials (FGM) structure, continuity, defect formation, microstructure, and mechanical properties of gradient regions. The investigation showed a strong, defect-free metallurgical bond between plain carbon steel and stainless steel 316 L and stainless steel 316 L and Inconel 625. The microstructure of stainless steel 316 L resulted from the solid-state transformation of ferrite-austenite (FA), with a significant presence of delta ferrite in the austenite matrix. In Inconel 625, the Laves intermetallic phase formed discontinuously between dendritic arms due to the microsegregation of alloy elements like niobium and molybdenum during solidification. The hardness values of Inconel 625, stainless steel 316 L, and plain carbon steel were 194–257 HV, 171–178 HV, and 159–170 HV, respectively. The ultimate tensile strength, yield strength, and elongation were achieved at 487 ± 10 MPa, 300 ± 6 MPa, and 40 % ± 0.15, respectively. The tensile test samples failed on the plain carbon steel side, indicating higher tensile strength at the interface and a well-bonded joint between the two alloys. Small, homogeneous dimples on the fracture surface confirmed the ductile fracture mode. The research demonstrates the use of wire-arc additive manufacturing (WAAM) to fabricate gradient materials with the required properties.

Recently, the automotive and aerospace industries have witnessed increased usage of titanium alloys. Nevertheless, the fabrication of titanium parts using conventional fabrication techniques is challenging owing to their low thermal conductivity, high affinity for oxygen, high melting temperature, high strength, and poor machinability. Advancements in welding technologies have resulted in the development of safe, efficient, and cost-effective joining techniques capable of overcoming the aforementioned challenges and enhancing titanium weld quality. The traditional approach and equipment used for welding aluminium and stainless steel had been utilized for joining titanium and its alloys but with limited success compared to the laser welding technique. Laser welding is the preferred method of welding because of its excellent qualities and great reliability, particularly for titanium alloy connections, which are frequently used in aerospace and aircraft structures. This work reviews recent works and progress recorded in laser welding of similar and dissimilar titanium alloy joints under varying processing parameters. The essential findings highlighting the impact of laser processing variables on the evolution of microstructural features, mechanical characteristics, and variations in corrosion resistance associated with laser-welded titanium joints in different environments are extensively highlighted. Finally, insightful information and prospects on laser welding of similar and dissimilar titanium alloy joints are provided.

This study investigated the tool's rotational speed effect during dissimilar friction stir welding of A390–10 wt.% SiC composite-AA2024 aluminum alloy on microstructure, mechanical properties, and corrosion resistance. The results show that the tunnel defect is created on the advancing side at low rotational speeds of 400 and 600 rpm due to insufficient material flow and a high rotational speed of 1200 rpm due to turbulent material flow in the stir zone. Finely equiaxed recrystallized grains are formed in the stir zone under a high plastic strain rate and particle-stimulated nucleation mechanism. The minimum hardness occurs in the TMAZ of the AA2024 aluminum alloy side, and by increasing the rotational speed from 800 to 1000 rpm, the average hardness in the stir zone decreases from 146.06±8.67 to 137.86±3.98 HV0.1. Also, by increasing the rotational speed from 800 to 1000 rpm, the stir zone's yield strength and ultimate tensile strength decrease by 4.9 and 5.2%, respectively. With the increased rotational speed from 800 to 1000 rpm, corrosion current increases from 0.0213 to 0.0225 mA.cm⁻², and corrosion resistance decreases by 17 %. After friction stir welding with a rotational speed of 800 rpm and traverse speed of 20 mm/min, the corrosion resistance of the joint increases and decreases compared to the composite base metal and AA2024 aluminum alloy base metal, respectively.

Friction stir welding is a modern welding technology with which the joining partners are welded in the solid state. The technology is often employed in the aerospace industry due to the excellent mechanical properties of the weld. Process disturbances can cause irregularities in the weld quality. It is still a challenge to avoid part fit-up deviations as a result of part misalignments and tolerances. Several publications have investigated the effect of alignment discrepancies on the weld quality, for example, by introducing a gap between parts, a tool offset, or linearly misaligned sheets. Depending on the application, the effects of simultaneously occurring alignment discrepancies on the weld quality could be critical. In this work, three alignment discrepancies were investigated (gap, linearly misaligned sheets, tool offset). The weld quality was determined using tensile tests. Process data such as the process forces and the spindle torque were also measured during the welding experiments. The results showed that each of the alignment discrepancies had a negative impact on the weld quality. The simultaneous occurrence resulted in an even lower weld quality. Some alignment discrepancies can probably be detected in the future using process data (e.g., the lateral force).

Metallic large-scale freeform lattice structures can be manufactured by wire arc additive manufacturing (WAAM). These structures are especially interesting for applications in civil engineering, such as lightweight structural elements and reinforcement structures. One promising approach for the efficient additive manufacturing of lattice structures is extending WAAM through drawn-arc stud welding (DASW). In this innovative combined process, called stud and wire arc additive manufacturing (SWAAM), WAAM is used for producing geometrically complex lattice segments (e.g., nodes) and DASW for straight segments. This paper presents the proof of concept showing the feasibility of this novel approach with a robotic test setup. Specimens consisting of bars with a diameter of 8 mm were produced with WAAM and SWAAM. The temperature development in the samples during manufacturing and their production time were measured. WAAM resulted for the first layer in a maximum temperature of 343 °C at a distance of 10 mm to the weld zone, while SWAAM showed 213 °C. The production time of a given test geometry was reduced by 57.7 % for the hybrid process compared to a pure WAAM manufacturing. This proves that reducing the welding operations by using studs decreases the heat input, lowers the process temperatures, and increases the production rate.

Plasma-Metal Inert Gas (MIG) hybrid welding was employed to carry out bead on plate welding of an aluminum alloy A5052. The plasma arc was ignited to form a keyhole, and a series of welding systems were developed starting with MIG welding. The convective patterns within the weld pool were meticulously analyzed. In addition, we conducted experimental observations of the flow inside and on the surface of the pool, and we were able to visualize the flow in some areas. The results indicated that the plasma welding side formed a pool that seamlessly integrated the plasma side and the MIG side. At the same time, we observed the formation of a flow pool that integrates both plasma and MIG sides, affecting the formation and behavior of the weld pool. This study aims to provide a nuanced understanding of flow dynamics across the entire pool. This approach is geared towards refining the intricacies of weld pool dynamics for the advancement of welding technologies.

The effect of inertial friction welding and continuous drive friction welding in joining SS 316 with Zn alloy is discussed in this article. Scanning electron microscopy was utilized to investigate the microstructure of the welding interaction. Energy-dispersive spectroscopy was utilized to identify the chemical composition of the element distribution at the interface. The findings reveal that a continuous drive friction welding process may produce SS 316 welded joints with Zn alloy. With a friction time of 35 s, the joint's tensile strength may reach 60 MPa. During the tensile test, all friction-welded samples failed at the interface. The fracture surface shows an almost flat surface and is not fibrous or brittle. Meanwhile, a new reaction layer from the intermetallic compound layer is not formed at the joint interface. The decrease in hardness in Zn alloys is due to the thermal softening effect caused by continuous heat from friction.