Heat treatment of 2024/3003 gradient composite and diffusion behavior of the alloying elements

A gradient composite 2024/3003, with external component of 3003 aluminum alloy and internal component 2024 aluminum alloy was prepared by double-stream-pouring continuous casting technique. Heat treatment of the composite material was investigated. Microstructures and alloying elements distribution were studied by means of scanning electron microscope (SEM), transmission electron microscope (TEM) and energy dispersive spectroscopy (EDS). The results show that the optimized heat treatment parameters for T6 state of the alloy are solution treatment at 768 K for 45 min, water quench and artificial age at 458 K for 12 h. There is a transition region between external component 3003 alloy and internal component 2024 alloy. During heat treatment, there are two kinds of diffusion behaviors, namely long distance and short distance diffusion in the transition region. At the solution treatment stage, dissolution of the intermetallic compound and homogenization of the microsegregation are the main process. The long distance diffusion is relatively weak because it strongly depends on the solution temperature and time. At the artificial aging stage, the short distance diffusion accompanied by precipitation reaction is the main process.