Abstract
The macro- and microstructures, the distribution of chemical elements and of the values of the microhardness over the width of the zones of remelting and heat-affected zone have been studied after the laser welding of sheets of an Al–Mg–Li alloy. It has been shown that the material of the zone of remelting (1.2 mm thick) represents in itself finely dispersed misoriented dendrites, in the primary branches of which particles of the strengthening δ′ phase (Al3Li) with dimensions of no more than 10 nm and in the interdendrite spaces, dispersed particles of the S phase (Al2MgLi and FeAl2) have been revealed. The hardness of the material of the zone of remelting was 108–123 HV 0.05; the hardness of the basic alloy, 150–162 HV 0.05. In the heat-affected zones of thickness 2 mm, the primary recrystallization occurred only in a narrow zone directly at the boundary with the weld. The strength of the welded junction was 470–490 MPa, which corresponds to the regulated degree of strength of the aluminum alloys of this class. The relative elongation of the material of the weld proved to be considerably less than that in the alloy matrix because of the microporosity of the weld material. It is shown that the convective stirring of the melt in the welding pool upon the laser welding made it possible to avoid the appearance of macroscopic defects, but on the microlevel there are observed micropores in the form of spheres with dimensions of 5–50 μm. The solidification of the alloy occurred in such a way that the dendrites had time to grow around the gas bubbles prior to their collapse, forming a sufficiently strong carcass. Inside the dendritic carcass, there have been revealed coarse inclusions (to 200 μm) that consist of oxides (Al2O3, Fe2O3, MgO, SiO2, CaO), of an iron-based alloy, and of the host aluminum alloy.
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Original Russian Text © N.B. Pugacheva, N.P. Antenorova, E.I. Senaeva, 2015, published in Fizika Metallov i Metallovedenie, 2015, Vol. 116, No. 12, pp. 1319–1329.
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Pugacheva, N.B., Antenorova, N.P. & Senaeva, E.I. Study of the structure and properties of laser-welded joints of the Al–Mg–Li alloy. Phys. Metals Metallogr. 116, 1259–1269 (2015). https://doi.org/10.1134/S0031918X1512008X
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DOI: https://doi.org/10.1134/S0031918X1512008X