Influence of Yb on the Phase Composition and Mechanical Properties of Low-Scandium Al–Mg–Mn–Zr–Sc and Al–Mg–Cr–Zr–Sc Alloys

Abstract

The microstructure, phase composition, and mechanical properties of new low-scandium Al–6.0Mg–0.2Mn–0.05Sc–0.25Zr–0.3Yb and Al–6.0Mg–0.2Cr–0.05Sc–0.25Zr–0.3Yb alloys have been studied. Ytterbium leads to the formation of a quaternary phase (Al, Mg, Yb, Si) of crystallization origin in the Al–6.0Mg–0.2Mn–0.05Sc–0.25Zr–0.3Yb alloy. Phases have been detected in the Al–6.0Mg–0.2Cr–0.05Sc–0.25Zr–0.3Yb ingot, (Al, Fe, Si), (Al, Mg, Yb, Si), and (Al, Fe, Yb). The greatest strengthening has been achieved in ingots after annealing at 440°C for 10 hours owing to the precipitation of Al3(Sc, Zr, Yb) dispersed inclusions (L12 phase). The optimal combination of strength characteristics and plasticity have been reached in the rolled sheet made of Al–6.0Mg–0.2Cr–0.05Sc–0.25Zr–0.3Yb alloy by annealing at 200°C for 1 hour: yield stress of 356 MPa, ultimate tensile strength of 443 MPa, and elongation of 10.5%.