Second Phase Dissolution and Grain Characteristics of As-Cast Al-Cu-Li Alloys with Different Mg Contents during Homogenization

Abstract

Homogenization treatment is usually indispensable to obtain a good microstructure pattern and brilliant final performance of Al-Cu-Li alloys. In the present study, the effect of different Mg contents on the microstructure of Al-Cu-Li alloys during homogenization was investigated utilizing optical microscopy (OM), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and differential scanning calorimetry (DSC) analysis. The results indicated that the higher Mg content changed the type of grain boundary phase in the as-cast alloy. The eutectic phases in the low Mg alloy were dominated by Cu-rich phases while the high Mg alloy also had many Ag-containing Al2CuMg phases. The difference in Mg contents did not affect the grain morphology, while the high Mg content in the Cu-rich phase caused a decrease in its melting point. Suitable homogenization treatments for the low and high Mg alloys are 520 °C/12 h and 495 °C/24h + 505 °C/48 h, respectively. This provides a reference for studies related to the effect of composition evolution on the dissolution of the second phase during the homogenization treatment.