Effect of Doping with Refractory Rare-Earth Metals on the Structure and Properties of Al-5Zn-3Mg Alloys Produced by Powder Metallurgy And Casting Methods

Abstract

The effect of doping with transition refractory metals on the structure and properties of the Al–Zn–Mg alloys produced by different methods is studied. It is ascertained that the strength of especially cast alloys is increased by scandium and zirconium doping due to the modifying action of scandium that arrests recrystallization and precipitation of a fine-grained phase coherent with the Al₃(Sc_1–xZr_x) matrix; the strength of alloys obtained by powder metallurgy (PM) methods increases to a smaller extent, in which the ultra-high cooling rate of melt atomized by high-pressure water plays the basic role in forming the fine-grained structure. The strength of powder metallurgy alloys based on water-atomized powders is substantially higher than that of similar alloys produced by the conventional casting method (standard commercial cast alloys and alloys produced by granular technology). The advantages of PM alloys over cast alloys are especially prominent in the absence of scandium doping. The highest strength of the PM alloys with scandium (σ_в = 651 MPa and σ_0,2 = = 596 MPa) is shown by Al–5Zn–3Mg–0.5Mn–0.7Zr–0.3Sc. Among the PM alloys without scandium, the highest strength is shown by Al–5Zn–3Mg–0.85Zr–0.22Cr–0.17Ni–0.15Ti alloy (σ_в = 618 MPa and σ_0,2 = 553 MPa).