13th International Conference on Fracture June 16–21, 2013, Beijing, China 4. Conclusions For all measured S-N curves, a plateau exists in the regime of 5×106-108 cyc, and then the fatigue strength gradually decreases between 108 and 109 cyc. Therefore, only fatigue strength corresponding to 109 cyc can be determined. Compared with other alloys, the alloy with Y content of 2 wt% has the highest fatigue strength and its value is 105 MPa. Additionally, for all alloys, the fatigue crack mostly initiates at the surface or subsurface in the super-long fatigue lifetime regime. Acknowledgements This work was supported by National Natural Science Foundation of China projects under Grant No. 51171192 and No. 51271183, a National Basic Research Program of China (973 Program) project under Grant No. 2012CB067425 and an Innovation Fund of Institute of Metal Research (IMR), Chinese Academy of Sciences (CAS). References: [1] H. Mayer, M. Papakyriacou, Influence of porosity on the fatigue limit of die cast magnesium and aluminium alloys. Int. J. Fatigue, 25 (2003) 245-256. [2] G. Eisenmeier, B. Holzwarth, H. Mughrabi, Cyclic deformation and fatigue behaviour of the magnesium alloy AZ91. Mater. Sci. Eng. A, 321 (2001) 578-582. [3] K. Tokaji, M. Kamakura, Fatigue behaviour and fracture mechanism of a rolled AZ31 magnesium alloy Int. J. Fatigue, 26 (2004) 1217-1224. [4] Z.B. Sajuri, Y. Miyashita, Y. Hosokai, Y.J. Mutoh, Effects of Mn content and texture on fatigue properties of as-cast and extruded AZ61 magnesium alloys. Int. J. Mech. Sci, 48 (2006) 198-209. [5] T.S. Shih, W.S. Liu, Y.J. Chen, Fatigue of as-extruded AZ61A magnesium alloy. Mater. Sci. Eng. A, 325 (2002) 152-162. [6] D.K. Xu, L. Liu, Y.B. Xu, E.H. Han, The crack initiation mechanism of the forged Mg-Zn-Y-Zr alloy in the super-long fatigue life regime. Scripta. Mater, 56 (2007) 1-4. [7] D.K. Xu, L. Liu, Y.B. Xu, E.H. Han, The micro-mechanism of fatigue crack propagation for a forged Mg-Zn-Y-Zr alloy in the gigacycle fatigue regime. J. Alloys. Comps, 454 (2008) 123-128. [8] F. Yang, S.M. Yin, S.X. Li, Z.F. Zhang, Crack initiation mechanism of extruded AZ31 magnesium alloy in the very high cycle fatigue regime. Mater. Sci. Eng. A, 491 (2008) 131-136. [9] Z.P. Luo, D.Y. Song, S.Q. Zhang, Stengthening effects of rare-earths on wrought Mg-Zn-Zr-RE alloys. J. Alloy. Compd, 230 (1995) 109-114. [10] Z.P. Luo, D.Y. Song, S.Q. Zhang, Effect of heat-treatment on the stability of the quasi-crystal in a Mg-Zn-Zr-Y alloy. Mater. Lett, 21 (1994) 85-88. [11] D.K. Xu, L. Liu, Y.B. Xu, E.H. Han, Effect of microstructure and texture on the mechanical properties of the as-extruded Mg-Zn-Y-Zr alloys. Mater. Sci. Eng. A, 443 (2007) 248-256. [12] D.K. Xu, L. Liu, Y.B. Xu, E.H. Han, The fatigue behavior of I-phase containing as-cast -6-
RkJQdWJsaXNoZXIy MjM0NDE=