Effect of Sc and Zr on Al₆(Mn,Fe) Phase in Al–Mg–Mn Alloys

Abstract

The effects of Sc and Zr on the shape, size, and number density of Al₆(Mn,Fe) phase in Al–5Mg–0.7Mn alloys were investigated by this article. The results showed that Sc and Zr can form strengthening particles of Al₃Sc and Al₃(Sc,Zr), which have the effect of refining grains and modifying the morphology and distribution of Al₆(Mn,Fe) phase. The OM, SEM, and TEM images indicate that with the formation of primary Al₃Sc and Al₃(Sc,Zr), the shape of Al₆(Mn,Fe) became more regular, size of Al₆(Mn,Fe) became smaller, and the number density of Al₆(Mn,Fe) increased when compared with base alloy. Zr could motivate the precipitation of primary Al₃(Sc,Zr) and Al–5Mg–0.7Mn–0.2Sc–0.2Zr had better refining effect than Al–5Mg–0.7Mn–0.4Sc. The grain refinement and finely dispersed Al₆(Mn,Fe) phase can improve the mechanical properties such as yield strength and ultimate tensile strength and the corrosion resistance by the results of intergranular corrosion (IGC) also improved.

Fig. 7 OM of the IGC depth and SEM of the IGC surfaces: (a) S0Z0, (b) S2Z0, (c) S4Z0, (d) S2Z2.