Effect of Sc and Zr Additions on Dispersoid Microstructure and Mechanical Properties of Hot-Rolled AA5083

Abstract

5xxx aluminum alloys are traditionally considered non-heat-treatable. With the addition of Sc/Zr and multistep heat treatment, two kinds of dispersoids (AlMn and Al3(Sc,Zr)) were formed. The effect of Sc additions (0.08–0.43 wt.%) on dispersoid formation and mechanical properties of hot-rolled sheets was investigated. The results showed that tensile properties initially increased with increasing Sc addition. The yield strength (YS) and ultimate tensile strength (UTS) of the alloy with 0.16 wt.% Sc reached 295 and 411 MPa, respectively, showing improvements of 28% in YS and 8% in UTS compared to the base alloy. However, with a further increase of Sc, the tensile properties declined owing to the formation of a line/fan-shaped microstructure associated with discontinuous Al3(Sc,Zr) precipitation during solidification. The evolution of Al3(Sc,Zr) and AlMn dispersoids during heat treatment and hot rolling was characterized using scanning and transmission electron microscopies. Their influence on the mechanical properties of hot-rolled AA5083 alloys was discussed.KeywordsAluminum 5083 alloySc and Zr additionDispersoidsMechanical properties