Effect of trace Sc on high-temperature creep performance of spray-deposited Al-Zn-Mg-Cu alloy

In this work, the effect of trace Sc on the mechanical property and high-temperature creep performance of the spray-deposited Al-Zn-Mg-Cu alloy was systematically investigated. The experimental results showed that the microstructure of the deposited and extruded alloy was greatly refined by the addition of Sc. For the Sc-containing alloy, precipitates within grains and the width of precipitate free zone (PFZ) are similar with those of the Sc-free alloy, whereas the area fraction of the precipitates at the grain boundaries is dramatically decreased. Both the mechanical property and high-temperature creep performance can be simultaneously improved by the addition of Sc. After 0.2 wt% Sc was added, the ultimate tensile strength of 831 MPa and elongation of 10% can be obtained, while the steady-state creep rates reached 1.1 × 10⁻⁶/h and 1.8 × 10⁻⁵/h at 80 °C and 120 °C, respectively. Based on the microstructure observation, amount of fine and dispersed Al₃(Sc, Zr) secondary phase particles were generated by the addition of Sc. It indicated that the Sc microalloying can not only bring about additional strengthening effect, but also inhibited the dislocation migration and coarsening of precipitates at high temperature, leading to the enhanced mechanical and creep resistance performance.