Evolution of eutectic structures in Al-Zn-Mg-Cu alloys during heat treatment
(1. Analysis and Measurement Center, Harbin Institute of Technology, Harbin 150001, China;
2. Northeast Light Alloy Co Ltd, Harbin 150060, China)
2. Northeast Light Alloy Co Ltd, Harbin 150060, China)
Abstract: The evolution of the eutectic structures in the alloys with different copper contents during heat treatment was studied by scanning electron microscopy(SEM), energy dispersive X-ray spectroscopy(EDS), and differential scanning calorimetry(DSC). The as cast microstructures involve α(Al), eutectic(α(Al) + Mg(Al, Cu, Zn)2) and Al7Cu2Fe. The Al2CuMg particles form during heat treatment. The volume of coarse phases decreases quickly in the initial 12 h during heat treatment. The volume of coarse phases change a little at 400 and 420 ℃. Copper content has a great influence on the evolution of the eutectic. The coarse phases dissolve slowly in alloy with higher copper content.
Key words: Al-Zn-Mg-Cu alloy; Al2CuMg phase; eutectic structure; heat treatment