Effect of High-Power Intensity on Corrosion Behaviour of Aluminium—Steel Dissimilar Joints Made by Electron Beam Welding

Abstract

The automotive sector is keen on using lightweight components with aluminium–steel joints since it leads to reduced fuel consumption and lowered CO2 emission. However, huge variations in the metallurgical properties of aluminium and steel and the use of high energy beam processes such as electron beam welding for fabrication challenge the durability of the resultant joints obtained. The present work establishes the effect of high heat input applied during electron beam welding on the corrosion resistance of 5052 Al–galvanized mild steel lap joints. The study includes microstructural characterization of the weld interfaces using scanning electron microscope (SEM), hardness measurement near the interfacial regions using Vickers’s hardness tester. Results indicated the generation of Al–Fe intermetallic layer at the weld bead–mild steel interface whose width ranged between 2.8 and 10.5 µm from head to foot regions. The composition of the layer was confirmed by the elemental analysis that was done on the layer by Energy Dispersion Spectroscopy which was attached to SEM. The layer had shown a severe impact on the corrosion resistance of the joints when exposed to nitric acid for 24 h following ASTM G 67-04. The joints experienced de-bonding at the interface and have undergone a huge weight loss of 38.9 mg.