DSC and TEM Investigation of Precipitation Behavior in a Cold-Rolled Pre-Aged Al-Mg-Si-Cu Alloy

This study investigates the effect of cold rolling on precipitation behavior and mechanical properties in a pre-aged Al–Mg–Si–Cu alloy. Following pre-aging at 35 °C, samples were subjected to various cold-rolling reductions (0–80%) and subsequently aged at 160 °C. Hardness measurements reveal that increasing deformation significantly enhances peak hardness and accelerates aging kinetics, with the 80% cold-rolled sample reaching peak hardness within 6 h compared to 1 week for the undeformed condition. Differential scanning calorimetry (DSC) analysis shows that all precipitation peaks shift to lower temperatures with increasing level of deformation, accompanied by a reduction in activation energy and narrowing of the full width at half-maximum, indicating accelerated precipitation reactions. Transmission electron microscopy (TEM) observations demonstrate that cold rolling introduces a high density of dislocations, which act as preferential nucleation sites for precipitates. As a result, a refined and more uniform distribution of nanoscale precipitates is obtained, with increasing number density and decreasing size at higher deformation levels. The combined results indicate that deformation-induced dislocations play a critical role in modifying precipitation pathways, promoting rapid formation of metastable phases, and enhancing the overall strengthening response of the alloy.