In this paper, the S32101 duplex stainless steel welded joints were produced by a K-TIG welding system. The weld geometry parameters under different welding speeds were analyzed by combining the morphological characteristics of the keyhole. The microstructure and impact toughness of the base metal and weld metal zone under different welding speeds were studied. The experiment results show that the welding speed has quite an effect on the geometry profile of the weld. In addition, the characteristic parameters of the keyhole can effectively predict the geometry profile of the weld. The test results prove that the microstructure, Σ3 coincidence site lattice grain boundary, and phase boundary of ferrite and austenite have an effect on the impact property of the weld metal zone. When the proportion of the austenite, Σ3 coincidence site lattice grain boundary and random phase boundary increased, the impact property of the weld metal zone also increased.

In this paper, the microstructure and pitting corrosion resistance of S32101 duplex stainless steel keyhole tungsten inert gas welded joints with different heat inputs were studied. The electrochemical experiments were conducted in a 1 mol/L NaCl solution at room temperature. The pitting rupture potential of the heat affected zone and the weld metal zone under different heat inputs were tested. The research showed that with the increase of heat inputs, more ferrite was converted to austenite and the number and size of intragranular austenite grains in the weld metal zone increased. The austenite content of the heat affected zone and the weld metal zone increase with the increase of heat inputs, and the CrN and Cr2N in the heat affected zone and the weld metal zone were mainly precipitated in the ferrite, in the austenite and ferrite/austenite interfaces. The pitting rupture potential value of the heat affected zone and the weld metal zone were increased with the increase of heat inputs, and the pitting corrosion resistance of the heat affected zone and weld metal zone were also increased with the increase of heat inputs. The relationship between the position CrN and Cr2N, the austenite content and the pitting corrosion resistance were elucidated, and the initiation mechanism of the pitting was investigated. Additionally, in this work, the heat affected zone and weld metal zone made at 2.46 kJ/mm heat inputs had the best pitting corrosion resistance. The research results provided useful information for improving the pitting corrosion resistance of S32101 duplex stainless steel keyhole tungsten inert gas welded joints.

In this paper, metal inert gas (MIG) welding of 6082-T6 aluminum alloy with a thickness of 4 mm was simulated using a double ellipsoidal heat source. Based on the simulation results, the evolution of the microstructure, the strengthening mechanism of mechanical properties, and the corrosion characteristics of the welded joint were studied further. The thermal cycle curve of the welded joint was obtained through numerical simulation. When the heat input was 2.34–2.75 KJ/mm, the temperature of the welded joint reached the melting point of the material. With the increase in welding heat input, the weld metal (WM) organization changed from the dendrite to the cellular crystal transformation and presented a uniform distribution. The precipitation of the strengthened phase was inhibited at 2.75 KJ/mm. When the heat input changed from small to large, the tensile strength and toughness first increased and then weakened. Dimple distribution of tensile fractures was observed with a scanning electron microscope. When the welding heat input was 2.57 KJ/mm, the mechanical properties of the joint were the best. The tensile strength can reach 76.62% of the base material, and the elongation after breaking can reach 59.38% of the base material. However, it was concluded through studying electrochemical corrosion that the corrosion resistance of welded joints under this parameter was the worst. This may be caused by the presence of Cu, Fe, Si, Mg, and other compounds, and was proven to be Mg2Si through EDS analysis.

In this paper, a metal inert gas (MIG) shielded welding method was used for high-quality welding of 6063-T6 aluminum alloy sheet with a thickness of 2.5 mm. The welding process of MIG welding was accurately simulated and the welding temperature field and thermal cycle curve were calculated using a combination of Gaussian body heat source and double ellipsoidal heat source. As the welding current increased from 75 A to 90 A, the reinforcing phase precipitated under the microstructure of the joint gradually became larger and re-solidified into the body, resulting in a reduction in mechanical properties. When the welding current is 85 A, the pitting resistance of weld forming and weld area reaches its optimum. At this time, the tensile strength of the joint is up to 110.9 MPa, the elongation is up to 16.3% and the Vickers Microhardness is up to 46.9 HV.