On the crystalline and quasi-crystalline phase compounds in an Al–Li–Cu–Mg base alloy

The presence of the quasi-crystalline T2 (Al6CuLi3) as a major equilibrium phase in as-cast and heat treated Al–(2.2–2.5) wt% Li–1.2 wt% Cu–0.8 wt% Mg–0.12 wt% Zr alloys i.e. the widely studied compositions in the AA 8090 alloy having the composition range of Al–(2.2–2.7) wt% Li–(1.0–1.6) wt% Cu–(0.7–1.3) wt% Mg–(0.04–0.20) wt% Zr, is known. This article examines an AA 8090 alloy having varying Cu, Mg and Li concentrations to demonstrate that reduced Cu:Mg and Cu:Li ratios in the alloy composition tend to destabilize the quasi-crystalline T2 phase in favor of the Al–Li–Cu–Mg base C phase, having the tetragonal structure.