Age hardening and the potential for superplasticity in a fine-grained Al-Mg-Li-Zr alloy

Experiments were conducted to determine the age-hardening characteristics and the mechanical properties of an Al-5.5% Mg-2.2% Li-0.12% Zr alloy processed by equal-channel angular (ECA) pressing to give a very fine grain size of approx1.2 mu m. The results show that peak aging occurs more rapidly when the grain size is very fine, and this effect is interpreted in terms of the higher volume of precipitate-free zones in the fine-grained material. Mechanical testing demonstrates that the ECA-pressed material exhibits high strength and good ductility at room temperature compared to convential Al alloys containing Li. Elongations of up to approx550% may be achieved at an elevated temperature of 603K in the ECA-pressed condition, thereby confirming that, in this condition, the alloy may be a suitable candidate material for use in superplastic forming operations.