Effects of thermal exposure on the mechanical properties and microstructure stability of an Al-Cu-Mg-Ag alloy

Mechanical properties and microstructural evolution of an Al-Cu-Mg-Ag alloy during thermal exposure at elevated temperature were characterized by means of tensile tests, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observation. The tensile test results suggested that tensile strength (sigma(b)) and yield strength (sigma(s)) reduced with both increasing exposure time and temperature. When exposed at 150 degrees C, the Al-Cu-Mg-Ag alloy exhibits good structural stability due to the splendid thermal stability of the Omega phase. SEM results showed that the specimen was fractured in a combined manner of intergranular and transgranular fracture. TEM results suggested the reduction of mechanical properties of samples was attributed to the coarsening of Omega phase and the precipitation of theta phase during thermal exposure.