Achieving balanced mechanical-corrosion properties in laser-welded Al-Mg-Si-Cu alloy welds by Ti content optimization

• Achieving simultaneous improvements in tensile strength and corrosion resistance in laser-welded Al-Mg-Si-Cu alloy welds. • Ti addition increases hydrogen solubility, restricting its escape from the molten zone. • Ti addition promotes precipitation of Al 3 Ti and (Al, Si) 3 Ti phases at higher temperatures, providing more nucleation sites. • Al 3 Ti/(Al, Si) 3 Ti phases enhance corrosion resistance due to their similar electrochemical potential to the Al matrix. To overcome the trade-off between mechanical properties and corrosion resistance in laser-welded Al-Mg-Si-Cu alloy welds, this study investigates the effect of titanium content on the porosity, grain size, precipitated phases, mechanical properties, and corrosion behavior of laser-welded welds. The precipitation of Al 3 Ti/(Al, Si) 3 Ti in the weld acts as the heterogeneous nucleation sites, thereby significantly refining the grain structure, which improves the corrosion resistance. These Al-Ti phases also have a positive effect on the corrosion resistance of the weld, as the potential difference between them and the matrix is not significant. The increase in weld strength can be mainly attributed to grain refinement. An excessively high Ti content deteriorates the mechanical properties by increasing hydrogen solubility in the weld, thereby impeding hydrogen’s escape from the molten zone. Overall, the welds achieve the best combination of mechanical properties and corrosion resistance when the Ti content is 0.60 wt%.