Non-thermally treated Al-Mg based alloy is looked forward to as potential material for automotive body parts due to its ductility. In a previous report, the authors demonstrated that adding less than 0.5%Si together with Sr, Ti and B to Al-4.5%Mg-1.0%Mn based alloy was effective for obtaining alloy with low hot tearing susceptibility and fracture elongation over 10%. In this study, 0.12%, 0.19% or 0.36% of Si was added to the base alloy while the amount of Sr, Ti, and B was fixed to 0.020±0.005%, 0.08%, and 0.016% respectively. For each alloy composition, an automotive rear suspension part called lower link arm was produced by high pressure die casting. The susceptibility was evaluated by measuring the length of hot tearing in the lower link. Tensile test pieces were cut off from the bottom of the lower link. As a result, it was found that susceptibility could be suppressed for each Si content compared to the base alloy. Fracture elongation was about 15% when the Si content was 0.12% or 0.19%. When the addition amount of Si was 0.36%, fracture elongation was about 10%.
