Analysis of the Structure and Properties of Welded Joints Made from Aluminum Alloys by Electron Beam Welding (EBW) and Friction Stir Welding (FSW)

One of the new areas that requires extensive study of the structure and properties of welded joints is the heat-affected zone (HAZ). This issue is particularly important for new constructions made of aluminium alloys intended for battery housing for powering electric car engines. Modern welding methods, such as EBW and FSW, meet the requirements related to the high precision of the process and the quality of the welded joint itself. This article presents the results of an analysis of the structure and strengthening of the HAZ of chemically modified AlMgSi(Cu) alloys via EBW and FSW. Microstructural observation was performed via SEM for each welded joint to determine the morphology of the precipitates. In the HAZ, β-Mg2Si, Q-Al,MgCu,Si and α-Al,Fe,Si (Mn,Cu) phases with larger sizes and rounded shapes were visible than they were directly in the weld made via the EBW method. The joints produced by the FSW method were characterised by a wide weld area and an irregular weld line. Analysis of the crystallographic orientation via EBSD and grain orientation spread (GOS) revealed differences in the shape of the grains and the degree of recrystallisation in the weld area between the FSW and EBW methods. The distributions of HB (FSW) hardness and HV (EBW) microhardness measurements revealed a slight decrease in hardening in the HAZ. In joints welded by both methods, the hardness of the welds for alloys with increased copper and chromium contents increased by approximately 5%.