Influence of Cu and Ni addition on metallurgical, mechanical, and corrosion behavior of TIG welded Al-Mg-Si alloy

Al-Mg-Si alloys are widely used in the automotive and aerospace industries due to their favorable properties. However, improving their mechanical behavior and corrosion resistance while maintaining weldability remains a challenge. This study investigated the effects of Cu and Ni coatings on the microstructure, mechanical properties, and corrosion behavior of TIG-welded Al-Mg-Si joints. AlSi5 filler rods were electroplated with Cu and Ni coatings of varying thicknesses before welding. The welded joints were characterized using optical microscopy, SEM, microhardness testing, tensile testing, impact testing, and electrochemical corrosion testing. Cu content in the welds increased from 0.11 wt% (uncoated) to 0.92 wt% (thickest Cu coating), while a hybrid coating achieved 0.51 wt% Cu + 0.48 wt% Ni. The 0.69 wt% Cu sample exhibited the highest overall hardness, with up to 89.5 ± 1.9 HV in the upper weld zone, a 36.9 % increase compared to the uncoated sample. Tensile strength increased by 35.4 % for the 0.69 wt% Cu sample, reaching 295.5 ± 5.3 MPa, while impact toughness improved by 28.6 %. Corrosion resistance also improved with Cu content up to 0.69 wt%, with the corrosion rate decreasing by 44.9 % compared to the uncoated sample. Cu and Ni coatings significantly enhanced the microstructure, mechanical properties, and corrosion resistance of TIG-welded Al-Mg-Si joints.