Simultaneous enhancement of strength and ductility in Al-Zn-Cu casting alloy with trace Mg addition designed by first principle calculation

Abstract

The Al alloy containing 17 wt% Zn exhibits enhanced strength through Zn precipitation after casting without the need for further aging treatment. DFT (Density Functional Theory) calculations revealed that the addition of Cu and Mg elements to Al-Zn alloy has the potential to stabilize the Zn phase in the Al matrix and reduce the interface energy between the Zn precipitate and Al matrix. Based on these findings, 0.5 wt% Cu and 0.1 wt% Mg were added to the Al-17 wt% Zn alloy. The trace element level of 0.1 wt% Mg addition led to a significant increase in both yield and tensile strength, from 132 to 278 and from 248 to 310 MPa, respectively, compared to the Al-17 wt% Zn alloy with 0.5 wt% Cu. Furthermore, their ductility surpassed 11 %. The trace amount of Mg greatly increased yield and tensile strength, while Cu enhanced the ductility in the Al-Zn alloy after casting without any aging treatment