COPRECIPITATION HARDENING IN Al-Li-Cu-Mg ALLOYS

Abstract
The structural features of the matrix precipitates families governing the strength of Al-Li-Cu-Mg(-Zr) alloys within a wide composition range are discussed. The specific effects of alloying and heat treating on matrix coprecipitation of δ', GPB zones, S', S, T' or θ', T1, and T2 and the dependence of the solid solution decomposition sequence on cold working between quenching and ageing are illustrated by transmission electron microscopy results. Conventional artificial ageing treatments and selective reversion heat treatments, performed on both laboratory and commercial alloys, allow to evaluate the intrinsic contributions of matrix precipitates on complex coprecipitation hardening in industrial alloys.