In this paper, the morphological characteristics of arc plasma and droplet transfer during the alternating magnetic field-assisted narrow gap groove laser-MIG (metal inert gas) hybrid welding process were investigated. The characteristics of arc plasma and droplet transfer, electron temperature, and density were analyzed using a high-speed camera and spectrum diagnosis. Our results revealed that the arc maintained a relatively stable state and rotated at a high speed to enhance the arc stiffness, and further improved the stability of the arc under the alternating magnetic field. The optimum magnetic field parameters in this experiment were B = 16 mT and f = 20 Hz, the electron temperature was 9893.6 K and the electron density was 0.99 × 10¹⁷ cm⁻³ near the bottom of the groove, which improved the temperature distribution inside the narrow gap groove and eliminated the lack of sidewall fusion defect. Compared to those without a magnetic field, the magnetic field could promote droplet transfer, the droplet diameter decreased by 17.6%, and the transition frequency increased by 23.5% (owing to the centrifugal force during droplet spinning and electromagnetic contraction force). The width of the weld bead was increased by 12.4% and the pores were also significantly reduced due to the stirring of the magnetic field on the molten pool.

The tailored thermal heat-treatment process for Ti-6Al-4V alloy manufactured by laser–arc hybrid additive manufacturing can achieve desired microstructures and excellent mechanical properties for components. The effects of different heat treatment regimens on the microstructure and mechanical properties of Ti-6Al-4V alloy manufactured by laser–arc hybrid additive manufacturing are investigated in this study. Utilizing optical microscopy and scanning electron microscopy, we analyze the variations in microstructure with changes in heat-treatment parameters and explore the reasons for the changes in mechanical properties under different solutions’ treatment temperatures and cooling rates. The microstructure of Ti-6Al-4V alloy fabricated via laser–arc hybrid additive manufacturing was primarily composed of Widmanstätten α plate structures and a small amount of acicular martensite α′ within columnar β grains that grew outward from the substrate along the deposition direction. Following solution treatment and aging heat treatment, the microstructure transitioned to a typical high-performance net basket structure with significantly reduced α plate thickness, leading to noticeable enhancements in sample ductility and toughness. Specifically, when the solution treatment and aging treatment regimen was set at 950 °C for 1 h, followed by air cooling, and then aging at 540 °C for 6 h with subsequent air cooling, the average grain size decreased by a factor of two compared to the as-deposited samples, while the impact toughness increased by 66.7%.

In this study, an alternating magnetic field is applied in the narrow-gap laser-MIG hybrid welding of 2205 duplex stainless steel with a thickness of 25 mm to achieve the purpose of balancing the ration of the two phases, refining the grains and improving the corrosion resistance. With the help of OM, EBSD, TEM, and other microstructural analysis methods, the organization evolution of a 2205 duplex stainless steel narrow-gap laser arc hybrid weld under the effect of alternating magnetic field is revealed. The corrosion resistance of the welded joints is investigated by electrochemical tests. The results show that the use of a 40 mT applied alternating magnetic field can not only effectively inhibit the generation of porosity and unfused defects in the weld, but also that the addition of an alternating magnetic field improves the ratio of austenite to ferrite in the weld, and the ratio of the two phases is increased from 0.657 without a magnetic field to 0.850. The weld grain preferential orientation is affected by the magnetic field, and the weld austenite grains are shifted from the Goss texture to the Copper texture. Under the electromagnetic stirring effect of the applied magnetic field, the average austenite grain size decreased from 4.15 μm to 3.82 μm, and the average ferrite grain size decreased from 4.99 μm to 4.08 μm. In addition, the effect of the alternating magnetic field increases the density of twins in the organization. Electrochemical test results show that the addition of an alternating magnetic field increases the corrosion potential by 75.2 mV and the pitting potential by 134.5 mV, which indicates that the corrosion resistance of the cover-welded specimens is improved by the effect of an alternating magnetic field. The improvement in corrosion resistance mainly depends on the austenite grain refinement and the increase in the austenite content.

Laser-arc hybrid additive manufacturing (LAHAM) based on the synergistic interaction of laser and arc has vast potential applications due to the advantages of high precision and fast manufacturing speed. Titanium alloy is a kind of indispensable material in the aerospace and marine industries because of its superior performance. This study primarily investigates the effect of laser power on formability, microstructure evolution, and mechanical properties of Ti-6Al-4V, a titanium alloy fabricated by LAHAM. The results indicate that the material utilization of the Ti-6Al-4V wire first increases and then decreases with the increasing laser power, reaching a maximum value of 95.48% at a power of 1500 W. As laser power increases, the acicular martensite α′ content in the LAHAM samples decreases, while the α phase increases and exhibits a coarsening phenomenon. Tensile strength increases with the rise in laser power, reaching a maximum horizontal tensile strength of 1080 MPa and a maximum vertical tensile strength of 1100 MPa. However, elongation decreases with increasing laser power. Microhardness decreases with the rise in laser power. The increase in laser power enhances the bonding between deposition layers, significantly improving the tensile strength of the specimens.

An experiment was conducted on the laser-metal inert gas hybrid welding of 7075 aluminum alloy under alternating magnetic field assistance, in order to investigate the effect of the magnetic field on weld porosity defects in aluminum alloy. The internal porosity of the weld seam under different magnetic field conditions was compared and analyzed through radiographic inspection. The impact of the alternating magnetic field on the arc shape and keyhole dynamic behavior was observed and analyzed by high-speed photography. The results showed that without a magnetic field, the arc shape underwent continuous scaling during the transition of molten droplets, the keyhole root was unstable, and there were a large number of process-induced porosities distributed in the center of the weld. When the magnetic field strength was 10 mT, the keyhole was completely unstable, and the size of the internal porosities in the weld seam significantly increased while the number of porosities decreased. At a magnetic field strength of 20 mT, the arc exhibited a rotating oscillation behavior, the keyhole was in a stable open state, and no porosity was detected in the weld seam. Upon reaching a magnetic field strength of 30 mT, the keyhole was also in a root unstable state, but the collapse and recombination speed of the keyhole were faster than that without a magnetic field, and the size and number of internal porosities in the weld seam significantly decreased.