Microstructure, mechanical properties, and electronic simulations of steel/aluminum alloy joint during deep penetration laser welding

This paper presents microstructure and mechanical properties of deep penetration laser welding joints with/without Mn, Zr, or Sn powder in an overlap steel-on-aluminum configuration. Heats of formation, elastic modulus, and thermodynamic properties of intermetallic phases (IMCs) formed in joining steel to aluminum are determined by the use of first-principle calculation. A good agreement between the experimental results and theoretical predictions can be seen. In the case of adding Sn powder, no obvious porosity, cracks, and other defects are seen, and the layer thickness of IMCs is smallest among all the powders. In addition, the FeSn phase is formed at the steel/aluminum interface, the structure of FeSn is more stable than that of FeAl, and the ductility of FeSn is also better than that of FeAl; hence, mechanical properties of the welding joint are significantly improved.