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

The presence of the quasi-crystalline T-2 (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 T-2 phase in favor of the Al-Li-Cu-Mg base C phase, having the tetragonal structure. (C) 2004 Published by Elsevier B.V.