Bauman Moscow State Technical University, Moscow, Russia:

I. N. Shiganov, Professor at the Department of Laser Technology in Mechanical Engineering, e-mail: inshig@bmstu.ru
A. I. Misyurov, Associate Professor at the Department of Laser Technology in Mechanical Engineering
D. M. Melnikov, Associate Professor at the Department of Laser Technology in Mechanical Engineering

К. О. Bazaleeva, Associate Professor at the Department of Materials

This paper describes the results of a study that looked at the effect of laser shock processing on the structure of different regions of a weld joint, weld seam and the adjacent area produced by TIG welding on Al – Mg alloys. Metallographic and X-ray diffraction analyses helped understand the effect of laser pulses on the structural changes and phase composition. It is shown that when welding is done on the AlMg6 alloy the weld joint has a few zones with different properties. The location of the zones is constrained by maximum heating temperatures. Laser shock processing creates thin (thread-like) β-phase (Al₃Mg₂) precipitates in the structure of the heat affected zone. Microhardness testing of these zones showed a uniform structure along the depth of the affected layer. Stringers of proeutectoid constituents were observed in high plastic deformation zones. The authors also identified some β-phase depleted regions. A new proeutectoid constituent precipitated as a result of strain ageing, which is harder than the matrix or the α-phase, compensates for the reduced concentration of the β-phase. A series of X-ray diffraction studies was conducted, which produced X-ray patterns of the weld joint on the aluminium alloy before and after laser processing. The authors found only Al solid solution reflections in the raw material. The diffraction patterns after laser processing show additional maximums of low intensity and a changed profile of the α-solid solution lines. The structural and phase changes identified following laser processing combined with welding-related compressive stresses should lead to higher plasticity and structural stability of the heat affected zone while increasing the weld’s corrosion resistance.
This research was funded by the Russian Science Foundation under Grant No. 171901706.

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