Micro Observation of Dissimilar Joint Interface between Low Carbon Steel and Pure Aluminum Produced by Laser Pressure Welding

Abstract

Dissimilar metals joints of low carbon steel (SPCC) and pure aluminum (A1050) sheets were produced using the laser pressure welding method by changing the laser power and the roller pressure. The tensile shear strength and peel strength of welded joints were measured. The fractured interfaces of the joints were observed by SEM and analyzed by EDX. Moreover, detailed phases formed in the welded interface were investigated by TEM.
In the tensile shear test and peel test, the strengths of the joints yielded under the optimum welding conditions were so high that the fracture occurred in the aluminum base metal. The thicknesses of intermetallic compound layers were about 50 nm to 100 nm. In the TEM observation and electron diffraction pattern results, the amorphous phase and the intermetallic compounds consisting of Fe₂Al₅ and Fe₄Al₁₃ were observed. The welded zone was cooled rapidly due to the heat transfer from the welded zone toward respective base metals and rolls. Therefore, the amorphous phase was formed in the most rapidly cooled part. Moreover, the Fe₂Al₅ and Fe₄Al₁₃ phases were formed in the welded interface.