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

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 degrees C for 10 hours owing to the precipitation of Al-3(Sc, Zr, Yb) dispersed inclusions (L1(2) 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 degrees C for 1 hour: yield stress of 356 MPa, ultimate tensile strength of 443 MPa, and elongation of 10.5%.