Effect of impurities of Fe and Si on the structure and strengthening upon annealing of the Al-0.2% Zr-0.1% Sc alloys with and without Y additive

The effect of impurities of Fe and Si on the microstructure and kinetics of the change in the hardness during annealing of the cast Al-0.2% Zr-0.1% Sc and Al-0.2% Zr-0.1% Sc-0.2% Y alloys has been studied. It has been found that the presence of the impurities of Fe and Si in the Al-0.2% Zr-0.1% Sc alloy leads to a partial binding of scandium into the (Al, Fe, Si, Sc) and (Al, Fe, Sc) phases of crystallization origin and to the corresponding depletion of the aluminum solid solution of Sc. It has been shown that as a result, the strengthening is significantly decreases upon annealing. The addition of 0.2% Y into the Al-0.2% Zr-0.1% Sc alloy with impurities of Fe and Si leads to the formation of the Al3Y and (Al, Y, Fe, Si) phases, whereas Sc is completely dissolved in the aluminum solid solution. It has been shown that the addition of Y leads to an increase in the thermal stability of the alloys during annealing at temperatures of 250, 300, and 370A degrees C and eliminates the negative effect of impurities of Fe and Si.