Influence Of Ecap On Fatigue Behavior Of Mg-Zn-Zr-Gd Alloy

Equal channel angle pressing (ECAP) technology can substantially refine the grains by severe plastic deformation of pure shearing under the prerequisite condition of unchanging the cross section of materials, and has received more and more attention. As one of the lightest engineering structural materials, the magnesium alloys exhibit wide application prospect in industrial production. Therefore, the microstructures and low-cycle fatigue behavior of ECAPed Mg-5%Zn-0.6%Zr-3%Gd alloy were researched. And the morphologies of fatigue fracture surfaces were observed with scanning electron microscope, and the fatigue fracture mechanisms of ECAPed Mg-5%Zn-0.6%Zr -3%Gd alloy were determined.The results reveal that the ECAP can largely refine the microstructures. The average grain size of Mg-5%Zn-0.6%Zr-3%Gd alloy is about 2μm after one pass of ECAP, and is about 0.5μm after two passes of ECAP. In addition, the results show that the ECAPed Mg-5%Zn-0.6%Zr-3%Gd alloy with different passes and routes (A,BC,C)exhibits the cyclic strain hardening, cyclic stability and cyclic strain softening during fatigue deformation. In general, the ECAPed Mg-5%Zn- 0.6%Zr-3%Gd alloy after two passes with route A shows the longest fatigue lives at most applied total strain amplitudes. Moreover, the relation between elastic and plastic strain amplitudes with reversal cycles to failure of the ECAPed Mg-5%Zn-0.6%Zr-3%Gd alloy with different passes and routes exhibits a monotonic linear behavior, and can be described by the Basquin and Coffin-Manson equations, respectively. And under the fatigue loading condition with total strain control mode, the fatigue cracks initiate transgranularly on the surface of the fatigue specimens and propagate in a transgranular mode for the ECAPed Mg-5%Zn-0.6%Zr- 3%Gd with different passes and routes.