A Model for HAZ Hardness Profiles in AI-Li-X Alloys: Application to the AI-Li-Cu Alloy 2095

Abstract

In a previous paper (Ref. 1), details were presented of a theoretical model describing the evolution of the hardness profiles in the heat-affected zones (HAZ) of AI-Li-X weldments. The intent of the model was to qualitatively predict the general shape of such a profile, which indicates points of double inflection. In the present paper, experimental results are presented to validate the model. Panels of AI-Li-Cu Alloy 2095 in the peak aged (T8) condition were welded by the gas tungsten arc (GTA) process using AA 2319 filler metal. Conventional transmission electron microscopy (TEM) studies were conducted on specimens taken from specific points across the HAZ to estimate the relative ratios of T1 (AI2CuLi) and _8' (AI3Li) precipitates, as well as incoherent grain boundary phases. Electron probe microanalysis (EPMA) was used to determine the variation of concentrations of elements across the HAZ, while the hardness profile was determined using Vickers microhardness measurements. The hardness profile and the associated pattern of phases present agree well with the information predicted qualitatively by the previously described model.