Research On Low Cycle Fatigue Behavior Of Hot-Extruded Al-6.0%Zn-2.0%Mg-1.5%Cu-xY Alloys

In the aerospace and transportation and other fields, Al-Zn-Mg-Cu aluminum alloyget more and more people’s attention with excellent performance. Mainly due to thetoughness of such alloys, high strength and excellent properties such as hardness and iswidely used in these areas. Through a series of experiments on the thermal treatment incase of different extruded Al-6.0%Zn-2.0%Mg-1.5%Cu-xY alloys explore, analyze thealloy microstructure, mechanical properties and fatigue properties, in order to provide atheoretical basis for further study of Al-Zn-Mg-Cu aluminum alloy.The microstructural results can show that0.25%Y can increase the grains of theAl-6.0%Zn-2.0%Mg-1.5%Cu alloy. After T6treatment, the grains of the extrudedAl-6.0%Zn-2.0%Mg-1.5%Cu alloy growth quickly, while Al-6.0%Zn-m2.0%Mg-1.5%Cu-0.25%Y alloys keep the same size. Tensile tests results show the Al-6.0%Zn-2.0%Mg-1.5%Cu alloy ultimate tensile and yield strengths significantly increase withadding Y after T6treatment. The low-cyclic fatigue test results show cyclic stress responsebehavior of the hot-extruded Al-6.0%Zn-2.0%Mg-1.5%Cu-xY alloys with differentprocessing states exhibits cyclic strain hardening. After heat treatment, the behavior of thealloy exhibits cyclic stability during low applied total strain amplitudes.The addition ofrare earth element Y can enhance the cyclic deformation resistance of as-extrudedAl-6.0%Zn-2.0%Mg-1.5%Cu alloy at higher imposed total strain amplitudes, increase thecyclic deformation resistance of the alloy with T6states at higher applied total strainamplitudes. T6treatment can enhance the cyclic deformation resistance of the hot-extrudedAl-6.0%Zn-2.0%Mg-1.5%Cu alloy at higher imposed total strain amplitudes and increasethe cyclic deformation resistance of the hot-extruded Al-6.0%Zn-2.0%Mg-1.5%Cu-0.25%Y alloy at all imposed total strain amplitudes. The addition of rare earth element Y canprolong the low-cycle fatigue lives of the hot-extruded Al-6.0%Zn-2.0%Mg-1.5%Cu alloywith as-extruded state and T6state. T6treatment can enhance the fatigue lives of the hot-extruded Al-6.0%Zn-2.0%Mg-1.5%Cu-xY alloys at all applied total strain amplitudes.The results of the fracture surfaces show that the fatigue cracks initiate mode at the freesurface of fatigue specimens in a transgranular, and the hot-extrudedAl-6.0%Zn-2.0%Mg-1.5%Cu-xY alloys propagate transgranularly.