High efficiency Plasma Welding Technology of Aluminum Alloy for medium and heavy Plate improved by Zhongwu Welding Institute of Guangdong Academy of Sciences

Aluminum alloy has been widely used in aviation, aerospace, automobile, machinery manufacturing, shipbuilding and chemical industry because of its small specific gravity, high specific strength, good corrosion resistance to sea water, non-magnetism and good low temperature performance. the demand for aluminum alloy welded structures is also increasing day by day. however, the application of aluminum alloy in key structures is still restricted by many pores, large welding deformation and low efficiency in aluminum alloy welding process.

Recently, the researchers of the High Energy Beam Research and Development Center of Zhongwu Welding Institute of the Provincial Academy of Sciences have carried out research on the high efficiency plasma welding technology of aluminum alloy for medium and thick plates on the basis of Sino-Ukrainian international scientific and technological cooperation. The defects of aluminum alloy welding have been solved by using plasma-MIG hybrid welding and variable polarity plasma welding. Compared with the traditional welding methods, its corrosion resistance and fatigue performance have been significantly improved. It is expected to expand the application of this technology in ships, aviation and other key structures.

The microstructure and corrosion resistance of 5083 aluminum alloy welded by plasma-MIG coaxial hybrid welding are improved. Through the (EIS) test and analysis of electrochemical impedance spectroscopy, the results show that the corrosion resistance of the welded joint does not decrease, and the Nyquist diagram of the joint is more complex than that of ordinary materials, showing that there are two connected semicircles. Simulation analysis shows that the system consists of two RFT-C parallel circuits and two time constants. The resistance of weld metal is higher than that of base metal, and its corrosion resistance is better. The results of linear polarization (LP) and electrochemical impedance spectroscopy (EIS) curves are consistent. The analysis shows that using coaxial plasma and MIG arc as heat source, welding wire and MIG arc surrounded by plasma arc can make droplet transfer and droplet heat transfer to base metal more easily controlled, which not only has the synergistic effect of plasma and MIG welding, optimizes the welding joint structure and improves corrosion resistance, but also has high welding efficiency. This research progress provides a technical reserve and theoretical basis for the application of aluminum alloy in the field of marine engineering.

The forming and fatigue properties of 5083 aluminum alloy welded joints were improved by optimizing the process of variable polarity plasma welding. The results show that compared with the traditional tungsten inert gas welding joints, variable polarity plasma welding joints have higher endurance limit (MPa), analysis shows that the keyhole and variable current mode formed in the welding process are the key to ensure the deep penetration and improve the weld quality of aluminum alloy welds. On the whole, the microhardness of the weld zone does not change much, but there is local softening and layered distribution. The particle size, shape and distribution of the dispersed phase (Mg2Al3) and the second phase (Fe, Mn) Al6 are different in different regions, which have a significant impact on the properties of the joint. This research progress provides a technical reserve and theoretical basis for the application environment of aluminum alloy in long-term service conditions.

The above research results are published in the TOP journal "Journal of Materials Processing Technology" (JCR I) in the field of material science under the title of "Microstructure and fatigue behavior of variable polarity plasma arc welded Al-6.2Mg alloys" and "Microstructure and corrosion resistance of Al5083 alloy hybrid plasma-MIG welds" respectively. This research work is supported by Guangdong Science and Technology Project and Guangdong Academy of Sciences Science and Technology Project.