Effect of Trace Addition of Sn on the Precipitation Hardening in Al-Si-Cu Eutectic Alloy

The work is devoted to studying the effect of a Sn trace addition on the precipitation hardening after aging of the eutectic Al-7 wt.% Si-7 wt.% Cu alloy. The addition of Sn and Si has a catalytic effect on the precipitation hardening and provides for a significantly higher hardness as compared with the binary Al-Cu alloy. The addition of 0.2 wt.% Sn leads to the formation of a substantially finer precipitation structure compared with the ternary alloy. As a result, the yield strength of the Sn containing alloy is up to 30% higher after uniaxial tensile tests. The finer precipitation structure of the quaternary alloy can be attributed to the higher stabilizing effect of Sn due to its partitioning in the and phases. The measured solubility of Sn (about 0.10 at.%) is close to the reported solubility of Si in theta'.