In this article, the effect of process parameters on the microstructure and mechanical properties of AW5083 aluminum alloy weld joints welded by a disk laser were studied. Butt welds were produced using 5087 (AlMg4.5MnZr) filler wire, with a diameter of 1.2 mm, and were protected from the ambient atmosphere by a mixture of argon and 30 vol.% of helium (Aluline He30). The widest weld joint (4.69 mm) and the highest tensile strength (309 MPa) were observed when a 30 L/min shielding gas flow rate was used. Conversely, the narrowest weld joint (4.15 mm) and the lowest tensile strength (160 MPa) were found when no shielding gas was used. The lowest average microhardness (55.4 HV0.1) was recorded when a 30 L/min shielding gas flow rate was used. The highest average microhardness (63.9 HV0.1) was observed when no shielding gas was used. In addition to the intermetallic compounds, β-Al₃Mg₂ and γ-Al₁₂Mg₁₇, in the inter-dendritic areas of the fusion zone (FZ), Al₄₉Mg₃₂, which has an irregular shape, was recorded. The application of the filler wire, which contains zirconium, resulted in grain refinement in the fusion zone. The protected weld joint was characterized by a ductile fracture in the base material (BM). A brittle fracture of the unshielded weld joint was caused by the presence of Al₂O₃ particles. The research results show that we achieved the optimal welding parameters, because no cracks and pores were present in the shielded weld metal (WM).

In this work, the effect of a filler wire feed rate was studied with special attention to the proportion of porosity volume in the weld metal, microstructure, and mechanical properties. Butt laser weld joints were created using the Nd:YAG laser. Weld joints were produced with the AZ31 filler wire with a diameter of 1.2 mm. Decreasing the filler wire feed rate of the filler wire led to an increase in the porosity of the weld metal. Therefore, porosity is more likely to occur in laser welding without the use of a filler wire. Clear segregation of aluminium, manganese, and zinc was observed in the EDS maps and the local EDS line profile measurements. The precipitates formed were rich in Al and Mn or Al and Zn, compared to the matrix. They also show a large decrease in Mg content to minimum values ranging from 10 to 60 wt.% in the precipitates. To investigate pores in the weld metal of the weld joint, computed tomography was used. The highest volume of porosity was measured in weld joint no. 3. (0.63 mm³). On the contrary, the lowest porosity volume was detected in weld joint no. 1. (0.06 mm³). The largest width of the weld metal (2.25 mm) was measured if the filler wire feed rate was 130 cm/min. The highest average microhardness (82.5 HV0.1) was recorded in the weld metal of weld joint no. 1. In weld joint no. 3, a fracture occurred in the weld metal and the measured tensile strength was only 154 MPa.

In this research, studied was the microstructure of AW5083 aluminium alloy butt laser weld joint fabricated under the Ar + 30 vol. % He shielding gas. The light and electron microscopy, computed tomography, microhardness measurements and tensile testing were used for evaluation of the weld joint properties. Porosity volume in the weld metal (WM) was observed by the computed tomography (CT). The volume of porosity in the weld No. 1 was 0.05 mm ³ , while that in the weld No. 2 was 1.45 mm ³ . The width of the weld No. 1 was 4.69 mm, the average tensile strength was 309 MPa, and the average microhardness was 55.7 HV0.1. Polyhedral grains with an average grain size diameter of 48 μm were present in the heat-affected zone. The fusion zone (FZ) was of a dendritic structure with an average grain size of 20 μm. Three intermetallic compounds β-Al ₃ Mg ₂ , γ-Al ₁₂ Mg ₁₇ and Al ₄₉ Mg ₃₂ , which were identified by transmission electron microscope (TEM) analysis, were present in inter-dendritic areas of the WM. The weld joint was characterized by ductile fracture in the base metal (BM). In the FZ, a small number of Al ₂ O ₃ particles of irregular shapes were observed.

The presented article is focused on funding options of regional airports. It describes the provision of state aid to regional airports, and it defines the regional airport, its specifications, and problems. From the view of the present legislation, it evaluates the European Union legislation and its application, it also analyses the state aid provision in civil aviation. In the context of the ongoing Covid-19 pandemic, it describes the situation in air transport and solves the provision of state aid to regional airports in Slovak Republic. Based on acquired knowledge and information, it suggests the changes in the legislation, and it brings a new vision how to improve the situation of regional airports not only in Slovak Republic, but also in the world.