Effect of the Zr and Er Content on the Structure and Properties of the Al-5Si-1.3Cu-0.5Mg Alloy

The effect of zirconium and erbium additives on the structure and mechanical properties of the cast alloy Al-5Si-1.3Cu-0.5Mg after the quenching and aging of an ingot and of a deformed sheet has been studied. An increase in the zirconium and erbium content from 0.15 to 0.2 wt % each leads to a substantial modification effect comparable to that via modification with the master alloy AlTi5B1. The grain size decreases from 200 to 80 mu m in this case, while it reaches 750 mu m in the alloy free of additives. The studied alloys are of a much higher ultimate compression yield stress at both room temperature (290-295 MPa) and 200 degrees C (230-235 MPa) due to the smaller grain size and higher number of phases of crystallization origin. In this case, the formation of the erbium-containing phase, which is insoluble in the process of homogenization before quenching, slightly decreases the copper content in the solid solution. An increase in the zirconium and erbium content elevates the recrystallization-onset temperature and, at the same time, has no significant effect on the properties of deformed alloys after their quenching and aging: the yield strength is 271-285 MPa, the ultimate strength is 337-378 MPa, and the relative elongation is 6.7-17.5%.