Single Beam Laser Welding Research Articles

Evolution of bonding mechanism and fracture mechanism of Ti alloy-steel joint by dual-beam laser welding using Mg-RE (RE=Gd, Y) filler

In this paper, a novel coaxial continuous-pulsed dual-beam laser was proposed to join TC4 titanium alloy with QP980 high-strength steel, and magnesium alloy containing rare-earth elements (Mg-RE) was creatively as filler. The weld appearance, microstructure and mechanical properties of joints obtained by single-beam and dual-beam laser welding were compared and analyzed. And the evolution of bonding mechanism and the fracture mechanism with laser beam energy density was analyzed. The results showed that the appearance and mechanical strength of the joint obtained by dual-beam laser were better than that by single-beam laser. And the maximum tensile shear load of TC4/QP980 lap joint welded by dual-beam laser reached 303 N/mm, which was 124 % of that of single-beam laser welding. The bonding of Mg-RE with QP980 affected by temperature of laser welding and mainly depended on Gd and Y. They just diffused to QP980 under low power and reacted with Fe under high power. And the inter-diffusion of Zr of Mg-RE with Ti of TC4 produced to the bonding of Mg-RE with TC4. The roles of continuous laser and pulsed laser in dual-beam laser welding were revealed in this paper and it showed a great application potential of coaxial dual-beam laser welding technology in dissimilar metal joining.

Characterization of dissimilar aluminum-copper material joining by controlled dual laser beam

Laser welding affords many advantages during the manufacture of EV battery packs. Aluminum (Al) and copper (Cu) are welded using a dual laser beam with a core and ring of different powers. Given the very high reflectance of Cu and Al exposed to near-infrared lasers, the materials absorb only very small amounts of energy. Compared with single-beam laser welding, dual-beam welding significantly improves the surface quality by controlling surface solidification. Here, we focused on the quality of welded surface beads, the weld properties, and the tensile strength; we varied the output ratio of the core to the ring beam. The optimal conditions for Al6061 were a 700-W core beam, a 500 W ring beam, and a weld speed of 200 mm/s. For C1020P, the optimal conditions were a center beam of 2500 W, a ring beam of 3000 W, and a welding speed of 200 mm/s. During laser lap welding of Al-Al and Al-Cu, the bead width and the interfacial bead width of the joint increased as the output increased. The penetration depth did not significantly change, but small pores formed at the interface of the junction. Tensile tests were performed to demonstrate the reliability of the weld zone; computer simulations were performed to analyze the heat distributions under optimal heat input conditions.

Comparison of single-beam and dual-beam laser welding of Ti–22Al–25Nb/TA15 dissimilar titanium alloys

Laser beam welding (LBW) was used to join Ti–22Al–25Nb/TA15 dissimilar titanium alloys. The microstructure and mechanical properties of the welded joints under single and dual beam welding were analyzed and compared. In the mode of single laser beam, the fusion zone only consisted of B2 phase because of existence of β-phase stabilizer and rapid cooling rate of LBW. However, O phase was formed in the fusion zone while applying dual-beam laser welding due to decrease of the cooling rate. The microhardness distribution of the welded joint in dual-beam welding mode was consistent with that in single mode, but the hardness of the weld under dual laser beam was higher than that of single laser beam. In room-temperature tensile tests, the fractures all occurred in the weld, but the morphology exhibited a quasi-cleavage feature in single mode while the morphology was dimple fracture in the mode of dual laser beam. The tensile strength and elongation were both increased under dual-beam laser welding compared with those under single-beam laser welding.

Laser welding dissimilar materials of aluminum to steel: an overview

Joining aluminum to steel can lighten the weight of components in the automobile and other industries, which can reduce fuel consumption and harmful gas emissions to protect the environment. However, the differences of thermal, physical, and chemical properties between aluminum and steel bring a series of problems in laser welding. The main problems are how to control the thickness of the intermetallic compound layer and reduce or avoid the generation of pores, cracks, and thermal stresses which severely limit the mechanical properties of welded joints. Laser fusion-brazing technology utilizes the precise control of heat input with or without filler to partially melt the low melting temperature aluminum base material and promote wetting on the high melting temperature steel base material in order to achieve sound metallurgical by combining the advantages of fusion welding and brazing. Different forms of laser beam welding including single beam laser welding, dual-beam laser welding, and laser arc hybrid fusion-brazing welding are reviewed.

Trend and innovations in laser beam welding of wrought aluminum alloys

The drive toward fulfilling weight reduction obligation, superior weld quality requirement, and industrial manufacturing rationale has sprung up considerable interest in applying laser welding technology on aluminum alloys. Nevertheless, porosity, solidification cracking, and surface reflectivity have been the major banes of laser welding of aluminum alloys. However, literature has shown that positive efforts have been accomplished in reducing these fundamental concerns by adopting careful selection of welding procedure, modification of pure laser welding techniques, and the use of appropriate filler metal. Albeit, there is still upbeat progression on the application and improvement of laser welding of aluminum alloys. At present, laser welding technology has the potential of fulfilling industrial requirements in joining lightweight aluminum alloys because of its capacity for automation and intrinsic flexibility, precision and repeatability, low general heat input, high welding speed, and low weld distortion. As a result, this report examines the available and current status of laser technologies in welding aluminum alloys. It further categorizes the laser technologies of aluminum alloys into four assemblages, namely, pure or single-beam laser welding, laser-arc hybrid welding, tailored heat source laser welding, and other innovative laser welding technologies, respectively. Mechanical, corrosion, and microstructural behaviors of laser welded aluminum alloys are also studied. Conversely, some of the research areas that need further investigations are proposed. Corrosion behavioral properties, influence of micropores on fatigue and quasi-static tensile strength, and toughness characterization of laser welded aluminum alloys are insufficient in literature.

Interface microstructure and fracture behavior of single/dual-beam laser welded steel-Al dissimilar joint produced with copper interlayer

Dissimilar metal welding of Q235 low carbon steel and 5052 aluminum alloy was carried out by a single/dual-beam laser in a steel-on-aluminum overlap configuration with a copper interlayer. The weld appearance, microstructure, and fracture behavior of the joints made by the single/dual-beam laser welding were investigated comparatively. The results showed that dual-beam laser welding, compared with single-beam laser welding, had better process stability which made better weld appearance and bigger effective joining width which enhanced tensile capacity. With a copper interlayer, a contact reaction zone appeared between the copper interlayer and aluminum matrix, which enlarged effective joining zone. The microstructures of the welding joint welded by a single/dual-beam laser were composed of the ligulate fusion zone with Fe-Al interface and the contact reaction brazing zone with Al-Cu interface. The Fe-Al interface mainly consisted of α-Al and Al2Cu eutectic structure, FeAl, FeAl2, and a certain amount of Al-Cu intermetallics, Fe2Al5 and FeAl3. The Al-Cu interface mainly consisted of eutectic phase Al2Cu and metastable phase of Al-Cu intermetallics. The tensile property was enhanced by a dual-beam laser, and the addition of the copper-foil interlayer might improve the metallurgical reaction of interfacial reaction region and promote the load-carrying ability of weld joint. An ideal joint with fewer defects could be obtained when the welding speed is 0.9–1.25 m/min of dual-beam laser welding and 1.5–1.75 m/min of single-beam laser welding.

Self-consistent modeling of keyhole and weld pool dynamics in tandem dual beam laser welding of aluminum alloy

A three dimensional model incorporating heat transfer, fluid flow and the keyhole free surface, Marangoni force, surface tension and recoil pressure is described. Possible multiple reflection Fresnel absorptions in complex keyhole profiles and laser plume interactions are also treated in the model. The results show that the keyhole is usually highly unstable and its depth undergoes severe oscillations in deep penetration tandem dual beam laser welding. The frequency of the depth oscillations is several kHz, which is comparable to that in single beam laser welding. Under the same heat input conditions, the amplitude of keyhole depth oscillations is smaller than that in single beam laser welding. Increasing the welding speed could improve the keyhole instability in dual beam laser welding. The mechanism of process stabilization of tandem dual beam laser welding over single beam laser welding is a joint effect of several beneficial physical factors, but not only the common known degassing effect. Good agreement is obtained between simulation results and prior experiments.