Enhancing the tensile strength and heat resistance induced by high-density Ω phases in an Al–Cu–Mg–Ag alloy

Abstract

For Al–Cu–Mg–Ag alloys, Ω phases play a crucial role in determining the mechanical property at room and elevated temperatures. In this work, an Al–5.5 wt.% Cu alloy with various Mg and Ag contents was prepared by casting and rolling. Combined with microstructure characterization and mechanical property test, the formation and stability of Ω phases and the change in tensile property of alloys due to the increase of Mg and Ag elements were discussed. The results demonstrated that Mg and Ag formed Mg–Ag clusters, which stimulated the precipitation of Ω phases in the Al–5.5 wt.% Cu–0.6 wt.% Mg–0.8 wt.% Ag alloy. As the Mg and Ag content increased to 1.0 wt.% and 1.2 wt.%, respectively, an improvement in stability of Ω phases and an increase in tensile property of the Al–5.5 wt.% Cu–1.0 wt.% Mg–1.2 wt.% Ag alloy were obtained. The tensile strength and elongation of the Al–5.5 wt.% Cu–1.0 wt.% Mg–1.2 wt.% Ag alloy was 533.1 MPa and 8.4%, respectively. In addition, the heat resistance and strengthening mechanisms induced by Ω phases were revealed. The generation of nano-sized Ω phases with a high density resulted in the significant second phase strengthening, thus acquiring the good tensile strength and heat resistant performance in the Al–Cu–Mg–Ag alloy.

Keywords

• Al–Cu–Mg–Ag alloy
• Mg–Ag cluster
• Nano-sized Ω phase
• Microstructure
• Heat resistance