Examining the effect of intermediate aging temperature on intermetallics, microstructure evolution, and recrystallization in a thermomechanically processed Al-Cu-Mg alloy sheet

In this research, distinct thermomechanical processing routes, encompassing primary annealing, cold rolling, intermediate aging, and final heat treatment have been devised. The primary goal was to explore the critical impact of short intermediate aging temperature on the evolution of intermetallic particles, microstructure evolution, thermal stability, and recrystallization in Al-Cu-Mg alloy samples. The findings demonstrated that while each thermomechanical step exerted a significant influence on the microstructure and particles' evolution, interestingly, the composition of particles remained relatively unaffected by the processing steps. Throughout the experimental procedures, two major intermetallic compounds, namely Al7Cu2(Fe,Mn) and AlCuMnFeSi were consistently identified. It was observed that intermediate aging successfully suppressed recrystallization implying the higher thermal stability of the aged samples. Analysis of the changes in the volume fractions of particles, their size distribution pattern, and samples' hardness revealed an optimal aging temperature of 170 degrees C, i.e., at which the lowest volume fraction of particles (6.33 vol%) was obtained concurrently with the greatest hardness (thus the highest thermal stability), as well as the lowest recrystallized fraction, hence effectively establishing an equilibrium between activation energy of precipitation and thermally activated diffusion mechanisms.