Unveiling the role of Sn in Cu-Zr Alloys: Influence on microstructure evolution and property tuning

This study comprehensively investigated the influence of Sn addition on the microstructure and properties of Cu-Zr alloys via transmission electron microscopy (TEM), atom probe tomography (APT), along with density functional theory (DFT) calculations. The results indicate that Sn addition reduces the solubility of Zr in the solid-state matrix during solidification, increasing the formation of Zr-rich eutectic particles and refining the grains of the as-cast 0.3Sn-doped alloy. During isochronal aging, the influence of Sn on Zr-rich precipitates varies with temperature. At lower temperatures (300–350 °C), Sn promotes the precipitation of Zr-rich precipitates while at higher temperatures (400–450 °C), Sn accelerates the growth of Zr-rich precipitates. DFT simulations show that Sn atoms preferentially segregate to the Cu side of the Cu/precipitate interfaces, facilitating the formation of core-shell structured precipitates without effectively impeding precipitate growth. Regarding electric conductivity, the difference between the 0.3Sn-doped and Sn-free alloys initially decreases and then increases with rising aging temperature. This is closely related to the change in the total segregation amount of Sn atoms on Zr-rich precipitates, which is associated with the size and numerical density of these precipitates. These findings offer novel insights for the composition design and processing parameter optimization of high-performance Cu alloys with core-shell structured precipitates.