Three-dimensional processing maps and microstructural evolution of a CNT-reinforced Al-Cu-Mg nanocomposite

The determination of the optimum processing window of a material at elevated temperatures is essential for metal forming. Such an “ideal” processing window could be characterized by the workability parameters of power dissipation efficiency, Ziegler's instability criteria, and the presence of favorable microstructures. The purpose of the present study is to develop three-dimensional (3D) processing maps of a 2.0 wt% carbon nanotube (CNT) reinforced 2024Al nanocomposite and to manifest continuous changes of power dissipation efficiency and flow instability domains involving key processing parameters of temperature, strain rate, and strain via isothermal compressive tests. The optimal hot working parameters of the 2024Al base alloy and the 2.0 wt% CNT/2024Al nanocomposite were identified to be at higher temperatures and lower strain rates, with a moderately smaller processing window for the nanocomposite due to the strengthening effect of CNTs and microstructural complexities. Instability occurred at higher strain rates and lower temperatures for both base alloy and nanocomposite. In the stable domain dynamic recrystallization was observed to occur, and the fraction of recrystallized grains increased with increasing deformation temperature, along with the presence of more random textures.