Effect of Sc and Zr addition on structures and mechanical properties of rapidly solidified 7090 based alloys

Abstract

Effect of minor addition of Sc + Zr has been studied on the structures and mechanical properties of rapidly solidified Al-9%Zn-2.5%Mg-1%Cu based alloys containing transition metals (Co, Fe, Fe + Ni, Mn). The amount of Sc and Zr addition was 0.2 mass% each. Rapid solidification was performed by gas atomizing and splat quenching onto a water cooled Cu single roll. Consolidation of the flakes was done by cold pressing, vacuum degassing and hot extrusion. Uniform distribution of Al3 (Sc, Zr) particles was observed by TEM in the as-extruded P/M materials with Sc + Zr addition. Hardness became higher for the as-extruded P/M materials with Sc + Zr addition than those without addition even after annealing at higher temperatures. Uniform distribution of Al3 (Sc, Zr) and η′ particles were observed in the T6 treated P/M materials. The size of η′ particle is smaller than Al3 (Sc, Zr) particle. The T6 treated P/M materials with Sc + Zr addition showed higher hardness than the as extruded materials. However, T6 treated alloys with Sc + Zr addition did not always show higher tensile strength and fatigue strength than those without addition.