Modelling of the Precipitated Phases and Properties of Al-Zn-Mg-Cu Alloys

The effects of Zn and Mg variations on the precipitated phases and the properties of Al-Zn-Mg-Cu alloys are investigated in this study. The quantities of stable and metastable phases have been calculated under various Zn and Mg contents by using software package JmatPro. The results show that the amount of the main hardening η (MgZn2) phase and η′ phase increase with higher Zn and Mg contents. T (AlCuMgZn) phase and metastable counterpart significantly increase with the reduction of Zn contents or the increase of Mg contents. S (Al2CuMg) phase reduces gradually with the increase of Mg content, while S phase varies only slightly with the Zn content. The precipitation of GP zones is promoted by the increase of Zn or Mg content. The physical and mechanical properties of the alloys have been modelled in such way that increasing Zn or Mg content could reduce electrical conductivity and thermal conductivity, while the mechanical properties improve with increasing Zn content and varies markedly as Mg content changes from 2.7 to 2.9 wt.%.