Microstructure and Mechanical Properties of the Extruded Al-Cu-Mn-Sc-Zr Alloy during Single-Stage and Two-Stage Aging

The evolution of microstructure and mechanical properties of hot extruded Al-5.5Cu-Mn-Sc-Zr and Al-6.5Cu-Mn-Sc-Zr alloys during solution and different aging treatments was investigated. The typical fibrous structure and elongated grains along the extrusion direction were observed in the two alloys. After solution and aging treatments, the proportion of large-size grains in the alloys increases slightly. The yield strength, ultimate tensile strength and elongation of the Al-5.5Cu-Mn-Sc-Zr alloy aged at 175 °C for 24 h are 400.8, 472.4 MPa and 13.9%, respectively. However, the growth and coarsening of the θ′ phase result in the decrease of strength of the Al-6.5Cu-Mn-Sc-Zr alloy. After 120 °C/6 h + 190 °C/3 h two-stage aging, the strength of the two alloys is equivalent to that of single-stage peak aging, while the time required is shortened. The two-stage aging has good application value in reducing aging time.