A Method to Predict the Precipitation Hardening Response of a Particle Strengthened Aluminum-Lithium Alloy

Abstract

Aluminum-Lithium alloys offer some attractive benefits over conventional aluminum alloys for aerospace structural applications. The benefits for the aerospace community include a weight-saving improvement as well as an increase strength and elastic modulus. The addition of lithium to aluminum increases the strength through heat treatment by a precipitation hardening process. This document describes an approach or method for predicting the precipitation hardening response for aluminum-lithium alloys using a given minimum number of experimental tests. The overall approach is based on the dislocation mechanics, particle coarsening, thermodynamics, and particle strengthening mechanisms applicable to precipitation hardened alloys. The method eliminates the need to know or determine several of the microstructural constants required for predicting the precipitation hardening response of a particle strengthened alloy. Thus, using the aluminum-lithium demonstration alloy, a minimum number of four tensile tests was utilized to predict the variation in strength with aging time, aging temperature, and composition, for the underaged, peak-aged, and overaged conditions.