The effect of copper addition on the structure and strength of an Al-Li alloy

In this study the effect of copper addition on the structure, precipitation kinetics and hardness in the Al-Li and Al-Li-Cu alloys aged at 200 degrees C was investigated. The structures of precipitates were studied using X-ray-small-angle-scattering (XSAS) and transmission electron microscopy (TEM) methods. The changes in the structure parameter (Rg) of both alioys was calculated using two methods, the Guinier approximation and correlation function gamma(r). By use of a plot of r gamma(r) the distribution law of the T-1 disc thickness was obtained and the coexisting spherical particles of delta' were estimated. Two types of delta' precipitates of approximately 2 nm size and above 8 nm and the T-1 precipitates of thickness between 3 and 4 nm were observed. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.