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Investigation of strengthening mechanism of commercially pure titanium joints fabricated by autogenously laser beam welding and laser-MIG hybrid welding processes
摘要： In this study, in order to achieve a better understanding of the strengthening mechanism in the commercially pure (CP) Ti welds, autogenously laser beam and laser-MIG hybrid welding of 4.2 mm thick CP-Ti plates were performed and the correlation between microstructure, texture distribution and the mechanical properties were systematically investigated. Microstructural coarsening and increase in microhardness were observed in the HAZ and WZ. The tensile test results suggested the base metal was the weak point of the joint for both welding conditions. The EBSD observations confirmed that a large number of 1012 and 1122 twin grains occurred in the HAZ and WZ of both welded joints, while a higher concentration of these twin grains were found in the laser-MIG hybrid joints. High concentration of the twin grain boundaries can act as barrier to stop dislocation slip during deformation and therefore contribute to the strengthening of the welds. The existence of very small twin grains and acicular α phase in HAZ and WZ would equivalently reduce the averaged grain size and therefore induce an increase in strength based on Hall-Petch’s law. In addition, the averaged Schmid factor of BM is higher than that of the WZ and HAZ in both welding joints suggesting that the grain boundary sliding will take place preferably in BM during deformation so that the necking and fracture occurred in base metal during tensile tests of both welding joint specimens.
关键词： Texture,Mechanical property,Laser-MIG hybrid welding,Strengthening mechanism,Commercially pure titanium,Laser beam welding,Microstructure
更新于2025-11-28 14:24:20
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Effect of graphene on corrosion resistance of Micro-arc oxidation coatings on 6061/7075 dissimilar laser-MIG hybrid welded joint
摘要： Corrosion behavior of a laser-metal inert gas hybrid (Laser-MIG) welded joint with dissimilar aluminum alloys was investigated. Micro-arc oxidation (MAO) coatings with and without graphenes were prepared on the surface of the welded joint. The effects of graphenes on the structure and corrosion resistance of the MAO coatings were studied. The welded joint was divided into five zones to investigate corrosion inducements in different zones. The heat-affected zone of 7075Al (7-HAZ) was found to be most susceptible to corrosion. Although the substrates in different zones had heterogeneous microstructures and phase compositions, the MAO coatings in different zones displayed relatively uniform surface morphology, structure, and phase composition. The MAO treatment significantly improved the corrosion resistance of welded joints. In addition, ceramic-graphene composite coatings exhibited slightly better corrosion resistance than a simple coating without graphenes due to structural changes in the coating.
关键词： Corrosion resistance,Aluminum,Graphene,Laser-MIG hybrid welding,Micro-arc oxidation
更新于2025-11-21 11:18:25
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Microstructure and mechanical properties of Ti/Al dissimilar joints produced by laser-MIG welding–brazing
摘要： We butt-welded AA6061 aluminum alloy to Ti6Al4V titanium alloy, dissimilar light metals, by using laser-MIG hybrid welding–brazing without grooves. The parameters of the laser and arc were optimized to produce sound joints with good formation and mechanical properties. The microstructure of the layer of intermetallic compounds (IMCs) was investigated by scanning electron microscopy and energy dispersive spectroscopy. We also tested the tensile strength of the joints with and without reinforcement. The morphology and thickness of the IMCs varied throughout the joints. A continuous thin layer of TiAl3 appeared on the top surface of the Ti6Al4V, on which some rod-like IMCs grew toward the fusion zone. In the upper region of the butt plane, because more heat accumulated there from the high-power laser coupled with the MIG arc, double-layer IMCs with a thickness of ～ 10.0 μm formed, composed of TiAl (near the Ti alloy) and TiAl3 (near the fusion zone). In the lower region of the butt plane, the double-layer IMCs became continuous and uniform, the serrated morphology disappeared, and the thickness of the IMC layer decreased to 4.0 μm. On the backside of the joint, the thickness of the compound layer (TiAl3) was about 1.0 μm. The average tensile strengths of the reinforced and unreinforced joints were 226 MPa and 210 MPa, respectively, which are up to 88% and 81% of the AA6061 tensile strength, respectively.
关键词： dissimilar joint,titanium alloy,intermetallic compounds.,Laser-MIG hybrid welding–brazing,aluminum alloy
更新于2025-09-23 15:22:29
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Behavior and stability of droplet transfer under laser-MIG hybrid welding with synchronized pulse modulations
摘要： In order to explore the synergetic effect on the process combination of pulsed laser and pulsed MIG hybrid welding, two kinds of coupling modes were performed by modulating the laser power to synchronize the arc current. The results showed that under the in-phase coupling mode, the addition of a high power laser during the peak period of the arc current increased the formation and separation time of the droplet and resulted in the deviation of droplet from the wire axis. This caused the droplet to be easily hit by the laser beam and reduced the stability of the droplet transfer. Moreover, the enlarged laser-induced plasma led to a significant loss of the laser energy. In contrast, under the anti-phase coupling mode, the application of a low power laser during the period of the highest arc current suppressed the arc length becoming longer and resulted in faster droplet separation, fewer weld spatters and smoother droplet transfer. At the same time, compared with the weld of in-phase laser-MIG hybrid welding, the weld of anti-phase laser-MIG hybrid welding had the advantages of deeper penetration, fewer weld spatters, less porosity and better tensile properties.
关键词： Droplet transfer,Synchronized pulse modulations,Laser-MIG hybrid welding
更新于2025-09-19 17:13:59
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Effects of groove constraint space on plasma characteristics during Laser-MIG hybrid welding of Titanium alloy
摘要： Laser-MIG hybrid welding with groove shows great potential in thick plate joining. However, the plasma behaviors in?uenced by the groove space are not well understood. In this paper, special stair-stepping plates with groove were designed to form di?erent groove con?gurations, and the e?ects of groove depth on the plasma characteristics were investigated systematically. The results showed that the plasma temperature decreased from 10,589 K to 8,527 K and the electron density increased from 1.30 × 1016 cm?3 to 1.44 × 1016 cm?3 when the groove depth increased from 0 to 20 mm. The reason may be that more laser-induced metal vapor, cooler than arc plasma, cannot leave the deeper groove space in time. The heat convection and radiation between the vapor and plasma resulted in the temperature decrease. Besides, as the groove constraint space increased, the plasma pro?le, frequency of droplet-transfer and weld width decreased, while the penetration depth increased to some extent. This research results would be inspirational and meaningful to the laser-arc hybrid welding of medium and thick plate.
关键词： Plasma,Titanium alloy thick plate,Laser-MIG hybrid welding,Groove constraint space
更新于2025-09-16 10:30:52
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Effect of helium-argon shielding gas in laser-metal inert-gas hybrid welded-brazed Al/steel dissimilar joint
摘要： Laser-metal inert-gas welding hybrid welding was applied to dissimilar butt joining of 304 stainless steel and 6063 aluminum alloy using three different shielding gas: 100% argon, 25% helium + 75% argon, and 50% helium + 50% argon. The influence of helium–argon shielding gas on the weld appearance and interfacial intermetallics layer of Al/stainless steel welding-brazing joint was discussed. The addition of helium can shrink arc, suppress laser plasma, and increase the stability of the droplet transfer process. Helium could not change the composition of the interface layer, which consists of θ-Fe(Al, Si)3 layer and τ5-Al7.2Fe1.8Si layer in the top, middle, and bottom regions of the joints. However, the interfacial intermetallics layer becomes thinner and the morphology was more uniform as the helium content changed from 0% to 50%. By analyzing the tensile fracture, it was found that the thicker θ-Fe(Al, Si)3 easily caused the fracture at the interface layer when using 100% argon. The highest tensile strength and the best ductility can be obtained by using 50% helium + 50% argon compared with that of joints obtained with 100% argon and 25% helium + 75% argon. Compared with joints welded in the pure argon atmosphere, the strength and ductility of joints increased by 18.4% and 191%, respectively.
关键词： laser-MIG hybrid welding-brazing,microstructure,composition of shielding gas,dissimilar materials
更新于2025-09-12 10:27:22