The effect of sc addition on microstructure and mechanical properties of as-cast Zr-containing Al-Cu alloys

Abstract

In this paper, the effect of Sc alloying on the microstructure and mechanical properties of as-cast Zr-containing Al-Cu alloys is investigated by microstructure characterization, thermal analysis and first-principles calculations, and the related mechanisms is discussed. The results show that when the Sc content is 0.3%, the grains and Al 2 Cu eutectic structure in the alloy can achieve the best refining effect. The strength and plasticity of the alloy are synergistically improved, and its ultimate tensile strength, yield strength and elongation are 211.3 MPa, 310.6 MPa and 6.3%, which are 43.5%, 35.1% and 50.0% larger than that of the base alloy (without Sc addition), respectively. When the Sc content is increased to 0.4%, the grain refinement is limited. This is because Al 3 (Sc,Zr) is coagulated, and the Al/Al 3 Sc interfacial energy is higher under Sc-rich conditions and the nucleation ability is poor. According to the calculation results of interfacial energy, the order of heteronucleation ability of α-Al is Al 3 (Sc,Zr)> Al 3 Zr> Al 3 Sc. And it is accompanied by a decrease in mechanical properties, which is because cracks are easily formed at the connection between the coarse W phase and the matrix, and stress concentration is easily caused during the deformation process. Furthermore, the solidification paths of alloys with different Sc contents are predicted by thermal calculation. When the Sc content is 0.3%, the alloy will generate metastable Al 3 (Sc,Zr) and stable Al 3 Sc during solidification. And the distribution of petal-like dispersoids is observed as linear clusters and blocky clusters in the experiment. • The microstructural refinement mechanism induced by Sc alloying is consummated based on experiments and first-principles calculations. • The evolution process of the precipitates in Al-Cu alloys with different Sc contents is elucidated by thermal analysis. • Microalloying is an effective method to increase the strength and ductility of as-cast high-Cu-content Al-Cu alloys.