Microstructure and Three-Point Bending Fatigue Behavior of Al-Cu-Mg-Ag Alloys with Various Mg Contents

This paper presents an investigation on the influence of Mg content on the microstructures, tensile properties and three-point bending fatigue behavior of Al-Cu-Mg-Ag alloys. The results indicate that the alloy containing 0.70 wt.% Mg possesses lower tensile properties and higher fatigue performance compared to the one with 1.15 wt.% Mg. Increasing Mg content in Al-Cu-Mg-Ag alloys can enhance the nucleation and precipitation of Ω phase, as well as increase the volume fraction and number density of constituent particles. The investigation of the fatigue crack initiation and growth behavior of Al-Cu-Mg-Ag alloy using interrupted fatigue tests suggests that micro-cracks mainly nucleate on Al2Cu constituent particles and the fatigue life is mainly associated with the density of constituent particles.