Quantifying the effects of Sc and Ag on the microstructure and mechanical properties of Al–Cu alloys

It is well known that the addition of Sc and Ag to Al alloys can promote the nucleation of α-Al grains and θ′-Al₂Cu precipitates. In this study, the effects of Sc and Ag on grain size and precipitates, as well as the contribution of grain refinement and precipitation strengthening to yield strength of Al–Cu alloys were quantitatively characterized. The addition of Sc refines the grain size and θ′ precipitate, resulting in the yield strength, ultimate tensile strength and elongation of Al–Cu alloy increasing to 314.2 MPa, 410.6 MPa and 6.31%, respectively. The addition of Ag increases the number density and volume fraction of Ω precipitate, resulting in the contribution of Ω precipitate to the yield strength increasing to 204.8 MPa, and the yield strength, ultimate tensile strength and elongation of Al–Cu alloy reaching 430.0 MPa, 449.9 MPa and 3.60%, respectively. The elastic modulus of AlCuMnMgTiAg alloy is increased to 73 GPa.