Highly interdependent dual precipitation and its effect on mechanical properties of Al-Cu-Sc alloys

Dual precipitation in a microalloyed Al-2.4 wt% Cu-0.1 wt% Sc alloy was investigated in comparison with single precipitation in binary Al-2.4 wt% Cu and Al-0.1 wt% Sc alloys, respectively. Although Al3Sc nanoparticles are more readily produced at higher aging temperatures in the binary Al-Sc alloys, the Al3Sc precipitation in the Cuadded ternary alloy was completely suppressed at 723 K while unexpectedly promoted at 573 K-aging. Meanwhile, a significant Sc-dependence of theta ' precipitation was also evidenced in the 573 K-aged Al-Cu-Sc alloy that the thickness of theta ' precipitates kept almost unchanged even to prolonged time, resulting in a high aspect ratio of >200 for the theta ' precipitates. The complex precipitation behaviors are rationalized in terms of strong interactions between the Sc and Cu solutes, which could be tailored to optimize the Al3Sc + theta ' dual precipitation and hence to improve mechanical properties. Moreover, the Sc atoms fully stabilized in Al solid solution by Cu solute at 723 K was discussed, and the high strength in Al-Cu-Sc alloy with dual precipitation was evaluated by quantifying the strengthen contribution from different strengthening mechanism.

Automated summary

The study compared single and dual precipitation phenomena in different alloys, finding that Al3Sc precipitation was completely suppressed at 723K in the Al-2.4 wt% Cu-0.1 wt% Sc alloy, but unexpectedly promoted at 573K. Moreover, significant Sc-dependence of theta' precipitation was observed in the Al-Cu-Sc alloy at 573K, with a high aspect ratio of >200 for the theta' precipitates.