A Multi-Mechanistic Model for Precipitation Strengthening in Al-Cu-Mg Alloys during Non-Isothermal Heat Treatments

Abstract

A multi-mechanistic model for microstructure development and strengthening during nonisothermal treatment of precipitation strengthened Al-Cu-Mg based alloys is derived. The formation kinetics of the precipitates is modelled using the Kampmann and Wagner numerical model that accounts for complete transformation from the nucleation to the coarsening stages. The increase in critical resolved shear strength of the grains due to the precipitates is based on two mechanisms i.e. the modulus strengthening mechanism for the shearable Cu:Mg co-clusters and the Orowan strengthening mechanism for the non-shearable S phase precipitates. The contributions due to solute and dislocation strengthening are also included in the strength calculations. The model is verified by comparing the predicted results with differential scanning calorimetery and hardness data on 2024 aluminium alloys. The microstructural development and strength/hardness predictions of the model are in reasonable agreement with the experimental data and the differences are discussed in terms of requirements for further model development.