A Model for Predicting the Precipitation Strengthening Response of Precipitation Hardened Alloys Strengthened by Ordered Precipitates

Abstract

A model was developed for predicting the precipitation hardening response of a particle strengthened alloy determined from the microstructure, composition, and heat treatment. The precipitates in the microstructure which impede dislocation motion and control the precipitation strengthening response as a function of the aging practice were used as the basis for determining the strength depending on the actual size distribution of particles. The particle size and distribution were determined from the microstructure via the heat treatment and composition. Consequently a micromechanical model was determined for predicting the variation in yield strength with aging time, temperature, and composition. The overall micromechanical model which was determined from the particle coarsening kinetics, dislocation mechanics, thermodynamics, resolved shear strength, as well as the particle strengthening mechanisms based on the dislocation particle shearing and dislocation particle looping interaction mechanisms was used to predict the strength of the demonstration alloy based on the microstructure. The demonstration alloy selected as the vehicle to model the precipitation strengthening response was a particle strengthened aluminum-lithium-zirconium alloy. Using this demonstration alloy, the overall model predicted from the microstructure the variation in strength with aging time, aging temperature, and composition, in the underaged, peak-aged, and overaged heat-treatments. The predicted aging curves were in good agreement with the experimental results for different aging practices.