Microstructural Characteristics and Mechanical Properties of Al-5Cu-0.4Mg-0.1Zr (-0.4Ag) Alloys Processed by...

The Al-Cu-Mg-Ag alloys have excellent specific strength, good heat resistance and have a wide range of applications in the aerospace and automotive industries. However, industrial production of such alloys is a great challenge owing to the addition of Ag, which limits their widespread application. In this work, the industrial continuous cast and continuous extrusion (Conform) processes were employed to prepare Al-5Cu-0.4Mg-0.1Zr (-0.4Ag) alloys, and the effects of Ag addition on the microstructural characteristics and mechanical properties during processing and heat treatment were investigated. The results indicated that Ag addition significantly refined grain size, increased high-angle grain boundary fraction and grain orientation difference in as-cast Al-5Cu-0.4Mg-0.1Zr (-0.4Ag) alloys, and suppressed excessive grain coarsening during homogenizing annealing. During Conform, Ag further refined grain size, increased subgrain number and enhanced grain orientation difference in extruded alloys. For the aging heat treatment, the T6 process demonstrated superior strengthening effects compared to the T5 process. Following T6 treatment, Ag promoted efficient and uniform precipitation of the Ω (Al₂CuMgAg) phase and then significantly enhanced peak hardness (160 HV) and tensile strength (511.46 ± 2.06 MPa). Additionally, Ag accelerated second-phase dissolution throughout the entire process and produced finer, denser ductile dimples on tensile fracture surfaces to gain good strength-ductility balance.