Effects of AlMn dispersoids and Al3(Sc,Zr) precipitates on the microstructure and ambient/elevated-temperature mechanical properties of hot-rolled AA5083 alloys

Abstract

With the addition of Sc and Zr to AA5083 alloy, two populations of strengthening particles (submicron-sized AlMn dispersoids and nanosized Al3(Sc,Zr) precipitates) precipitate during three-step heat treatment. Here, their influence on the microstructure and mechanical properties of hot-rolled sheets at ambient and elevated temperatures was investigated. The results show that the low-temperature (25–200 °C) tensile properties of the rolled sheets were significantly improved by increasing the Sc and Zr contents. The yield strength (YS) and ultimate tensile strength (UTS) of the alloy with 0.16 wt% Sc and 0.17 wt% Zr at ambient temperature reached 295 and 411 MPa, respectively, showing improvements of 30% in YS and 11.8% in UTS compared to the base alloy. However, the YS of the Sc/Zr-containing alloys at high temperature (300–400 °C) were lower than that of the base alloy. The mechanical properties of both the base and Sc/Zr-containing alloys were thermally stable during long-term thermal exposure at 300 °C for 500 h, demonstrating the great potential of this alloy for various elevated-temperature applications. The characteristics of the AlMn dispersoids and Al3(Sc,Zr) precipitates after the heat treatment and hot rolling were examined and quantified using transmission electron microscopy. Their combined contributions toward the YS at 25 and 300 °C were analyzed with the aid of constitutive strengthening equations and compared with experimentally measured values.