Quantifying the effects of Sn on θ′-Al₂Cu precipitation kinetics in Al–Cu alloys

In this study, the effects of 0.14 wt-% Sn on accelerating the precipitation kinetics during heat treatment are quantified. By calculating the activation energy of θ′ phase, it was found that the combined additions of Cu and Sn can reduce the energy barrier and increase the number density of the θ′ phase in the peak aged state, and thus improving yield strength and ultimate tensile strength from 239 and 318 to 445 and 457 MPa, respectively. Based on the quantitative analysis of the θ′ phase, it was found that with the combined additions of Cu and Sn, the average length of the θ′ phase increased from 18.11 to 25.82 nm, and the number density increased from 2.17 × 10²¹ to 4.62 × 10²¹ m⁻³.