EFFECT OF T1 PRECIPITATE ON THE ANISOTROPY OF AL-LI ALLOY-2090

Abstract

A study has been made of the effect of T1 precipitate on the anisotropy of an Al-Li alloy 2090. The critical role of T, precipitates has been identified by comparing the behavior of the alloy with various microstructures. These include (1) T8E41 tempered specimen with T1, theta' and delta', (2) reverted specimen with T1, (3) re-solutionized specimen with very fine delta', and (4) under-aged specimen with fine delta' and theta'. It has been shown that the {110} [112] crystallographic texture developed during thermomechanical treatment has a direct effect on the anisotropy. It also has an indirect effect by causing an inhomogeneous distribution of nucleation sites for T1 among four {111} habit planes during stretching and accordingly inhomogeneous distribution of T1 precipitates among four possible {111} planes during aging. Such inhomogeneously distributed T1 precipitates in both T8E41 tempered and reverted specimens affect the variation of tensile properties, particularly elongation with specimen orientation.