Effect of Be, Sr, Mn, Mg, Cr and Si Addition on Neutralization and Fragmentation of β-Al₅SiFe Phase in Al-(6–10) %Si Alloys

The aim of this work is to create a comprehensive database relating to mechanical properties (elastic limit, ultimate limit, and percentage elongation at the fracture) of Al-Si-Cu alloys (A319.2, B319.1, and A380). First of all, this involves specifying the effect of the iron content as well as evaluating the influence of the addition of modifying/neutralizing elements such as Sr, Be, Mn, Be + Sr, and Mn + Cr on the type 319 and 380 alloys having undergone T6 heat treatment. The second part, which relates to the eutectic alloy, studies the dissolution of the phase β-Al₅FeSi by evaluating the effect of the iron content, the influence of modification by Sr. The last step is to establish a link between the tensile properties obtained and the characteristics of the microstructures, i.e., the percentage of porosities and the length and thickness of the platelets/pads. In total, 68 different compositions were prepared with an average number of 6–8 test pieces/composition. Also, the mode of rupture was studied using the scanning electron microprobe. The results show that strontium (Sr), manganese (Mn), and beryllium (Be) make it possible to partially neutralize the harmful effects of iron. The Sr fragments the phase (β-Al₅FeSi then that Mn transforms the platelets into Chinese script). In addition, an Al₁₂Mn phase may precipitate within the α-Al (i.e., pre-dendritic phase). As for beryllium, it is effective in both refining the β-phase and transforming it into a new phase of type BeSiFe₂Al₈. A sum of 700 tensile bars were tested.