Influence of 0.5% Ag Addition on Low-Cycle Fatigue Behavior of Hot-Extruded Al-5Cu-0.8Mg-0.15Zr-0.2Sc Alloy Subjected to Peak-Aging Treatment

The total strain amplitude controlled low-cycle fatigue tests were performed at room temperature and 200 °C to clarify the influence of 0.5% Ag addition on the low-cycle fatigue behavior of an Al-5Cu-0.8Mg-0.15Zr-0.2Sc (in wt.%) alloy subjected to the peak-aging treatment after hot extrusion and solid solution treatment. The experimental results demonstrate that during low-cycle fatigue deformation, peak-aged Al-5Cu-0.8Mg-0.15Zr-0.2Sc(-0.5Ag) alloys exhibit cyclic hardening, cyclic stability, or cyclic hardening followed by cyclic stability, depending on the Ag addition, imposed total strain amplitude, and testing temperature. The addition of 0.5% Ag greatly increases the low-cycle fatigue life of peak-aged Al-5Cu-0.8Mg-0.15Zr-0.2Sc alloy, where the maximum rising amplitude is about 126.7% at ambient temperature and approximately 90.1% at 200 °C. Furthermore, it has been discovered that the addition of 0.5% Ag has no effect on the beginning and spreading modes of low-cycle fatigue fractures. For the peak-aged Al-5Cu-0.8Mg-0.15Zr-0.2Sc(-0.5Ag) alloys subjected to low-cycle fatigue deformation at different total strain amplitudes and testing temperatures used in this investigation, fatigue cracks initiate trans granularly at the free surface of the fatigue specimen and propagate in a trans granular mode.