Precipitates evolution and mechanical properties of high strength-ductility Al-4.9Mg-1.6Li-0.4Cu-0.3Zr-0.2Sc alloy

In this paper, the strength-ductility tradeoff was overcome in a designed Al-4.9Mg-1.6Li-0.4Cu-0.3Zr-0.2Sc (wt.%) alloy via tailoring the intragranular and intergranular precipitates. After ageing for 8-32h at 165°C, the fine Al3Li and Al3(Sc, Zr, Li) phases were formed intragranularly, which increased both the yield strength and strain hardening rate. Meanwhile, the banded distributed fine intergranular phases of Al2MgLi were formed, which reinforced grain boundaries by suppressing crack propagation, thus improving ductility of alloy. Based on these, the optimal comprehensive tensile properties of this alloy were obtained (Ultimate tensile strength = 538-577 MPa, Elongation = 14.0-18.9%), which are the highest values among the reported cast Al-Li alloy families at present.