Effect of beam oscillation on intermetallic compounds and mechanical properties of steel/aluminum laser welded joint

Brittle Fe-Al compounds limit the performance of the steel/aluminum joint. Beam oscillation laser technology was performed to control the thickness, morphology and distribution of intermetallic compounds (IMCs) at interface. The results showed that beam oscillation significantly reduced the thickness of IMC layer. When oscillation frequency was 10 Hz, the needle-like phase embedded in aluminum matrix was obviously passivated in the circular oscillation mode, while the needle-like phase at interface tend to distribute parallel to the layer-like IMC, and formed a "bite" connection effect with aluminum matrix. In the linear oscillation mode, the needle-like phase disappeared, and smooth and flat interface was obtained. Compared with the non-oscillation mode, in the case of circular or linear oscillation mode, the width of molten pool was significantly increased, the crystal grains were refined, and the joint property was increased by 26% and 17% respectively, which were caused by the combined effect of mechanical bonding and metallurgical regulation. The influence mechanism of beam oscillation on the thickness, morphology and distribution of IMC at interface was revealed by high-speed photography and finite element simulation, which provides a new idea for the welding of steel/aluminum dissimilar materials.