MICROSTRUCTURE CHARACTERISATION OF THE LASER-HYBRID-WELDED ALUMINIUM ALLOY EN AW-5454-D

Microstructural characterisation was performed on EN AW-5454-D Al-alloy weld samples made with a laser-hybrid-welding process in a horizontal position. For this purpose, two pre-bent Al-sheets were used, with different thicknesses of 3.5 and 4 mm. The microstructural characterisation included scanning electron microscopy with microchemical analysis and electron-backscatter diffraction, as well as optical microscopy. The characterisation revealed that the microstructure consists of a primary α-aluminium phase and a minor Al6Mn phase. A fine-grained microstructure was identified in the weld metal. Hardness measurements of HV 0.5 were performed in the weld joint, where the results revealed that the hardness was reduced in the weld metal and the heat-affected zone in comparison with the base metal. A theoretical calculation of the chemical composition in selected areas of the weld was performed, which was compared with the results of EDX microchemical analysis obtained for each element. The comparison showed relatively good agreement.