Cyclic deformation behavior of a high zinc-containing cast magnesium alloy

摘要

The objective of the present study was to evaluate strain-controlled low cycle fatigue behavior of a high zinc-containing Mg-10Zn-5Al (wt.%) cast magnesium alloy in relation to the microstructure characterized via EBSD and XRD. The addition of Zn with a Zn/Al ratio of similar to 2 suppressed the presence of beta-Mg17Al12 phase, and the as-cast alloy consisted mainly of primary alpha-Mg and eutectic-like tau-Mg-32(Al,Zn)(49) phase in a characteristic network form. The alloy exhibited superior tensile properties compared with several commercial cast alloys. Unlike extruded magnesium alloys, the alloy exhibited almost symmetrical stress-strain hysteresis loops due to the presence of tau-Mg-32(Al,Zn)(49) phase and nearly random textures. Although slight cyclic softening occurred at higher strain amplitudes, cyclic stabilization basically remained. This was also reflected by the nearly overlapped cyclic and monotonic stress-strain curves. The fatigue life predicted via strain energy based approach was in good agreement with the experimental value. Fatigue crack initiated from the near-surface imperfections, and crack propagation was characterized by fatigue striation-like features along with tear ridges.