Effects of Gd and Y additions on microstructure and properties of Al–Zn–Mg–Cu–Zr alloys

Three kinds of alloys Al–Zn–Mg–Cu–Zr, A1–Zn–Mg–Cu–Zr–Gd and A1–Zn–Mg–Cu–Zr–Gd–Y were prepared by cast metallurgy. The effects of Gd and Y additions on the microstructure and properties of Al–Zr–Mg–Cu–Zr alloys were investigated by optical microscopy (OM), tensile test, scanning electron microscopy (SEM), electronic probe microanalysis (EPMA) and transmission electronic microscopy (TEM). The results show that the combined additions of Gd and Y to the A1–Zn–Mg–Cu–Zr alloys effectively retard the mergence and growth of the sub-grain during the recovery process, significantly inhibit the recrystallization of Al matrix. σb, σ0.2 and δ are improved with increasing Gd and Y content, and the improving amplitudes reach 11.49%, 14.61%, 63.11% respectively and have better relative intracrystalline solubility.