A Study of Second-Phase Precipitates and Dispersoid Particles in 2024 Aluminum Alloy after Different Aging Treatments

Aluminum alloys such as AA2024 are popular in the automotive and aircraft industries. The application of artificial aging significantly improves their mechanical properties by precipitation hardening. However, commercial alloys very often contain different amounts of elements such as Si and Fe that make the evolution of the microstructure harder to control. Large intermetallic particles can influence the overall results of heat treatment and cause deterioration of material properties. The authors decided to examine changes in the microstructure of three commercial 2024 alloys with varying chemical compositions by applying three different types of aging treatments. The results show considerable differences in the amount, size and morphologies of the precipitates. Second-phase Al(2)Cu and Al(2)CuMg precipitates were identified in one of the alloys. Other interesting types of multiphase particles were discovered in alloys with higher Si contents. The results show that even small variations in the composition can lead to a completely different microstructure.