Addressing the strength-ductility trade-off in a cast Al-Li-Cu alloy-Synergistic effect of Sc-alloying and optimized artificial ageing scheme

A dramatic improvement of strength and ductility of cast Al-2.5Li-1.5Cu-1Zn-0.5Mg-0.15 Zr alloy was obtained by the collaboration of Sc-alloying and optimized ageing scheme. Joint and independent influence of Sc-alloying and different ageing temperatures were investigated. The results revealed that a substantial increase was realized in the hardness of Sc-containing alloy, and the ageing response time was only influenced by ageing temperature. Coarse and heterogeneous delta' (Al3Li), wide delta'-precipitation free zones (delta'-PFZs), and a large amount of T1 (Al2CuLi) precipitates were observed in Sc-containing alloy aged at 175 degrees C, which resulted in superior yield strength and poor elongation. The Sc-containing alloy obtained an excellent combination of ductility (elongation = 8.2 %) and tensile strength (ultimate strength =565 MPa) suffered to 150 degrees C ageing for 64 h. The increase in the elongation was mainly due to the combined effect of grain refining, much finer delta', and extremely narrow delta'-PFZs (<10 nm), while the higher strength was mainly attributed to the formation of Al3(Sc, Zr, Li) composite particles and a large amount of S' (Al2CuMg) phase. However, the enhancement of the different ageing temperature (150 degrees C and 175 degrees C) on the mechanical properties of the alloys without Sc addition was not obvious. (c) 2022 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Automated summary

The combination of Sc-alloying and optimized ageing scheme resulted in a significant improvement in the strength and ductility of the cast aluminum alloy. The presence of Sc in the alloy contributed to increased hardness and superior mechanical properties, while different ageing temperatures influenced the alloy's response time.