Impact of Cu/Mg ratio on thermal stability of hot extrusion of Al-4.6 pct Cu-Mg-Ag alloys

This work explores how the Cu/Mg ratio affects the thermal stability of the extrusion of Al-4.6 pct Cu-Mg-Ag alloys at aerodynamic heating temperatures of up to 155 degrees C for 1000 hours. The Cu/Mg ratio was modified by adding various amounts of elemental Mg. The alloy microstructures, which determine thermal stability, were analyzed with an optical microscope, an electrical conductivity meter, a differential scanning calorimeter (DSC), and a transmission electron microscope. Experimental results indicate that reducing the Cu/Mg ratio of the alloy by the further addition of Mg causes Omega to become the primary strengthening phase after aging treatment, increasing the hardness and the thermal stability, although the theta' phase is suppressed. The S phase does not affect the thermal stability of the alloy, because it is present in only a low quantity. Results of this study also demonstrate that the hot-extruded low Cu/Mg alloy satisfies the requirement of the material thermal stability of commercial supersonic aerial applications.