title: Fatigue behaviors of HP-Mg, Mg-Ca and Mg-Zn-Ca biodegradable metals in air and simulated body fluid.
abstract: The dynamic loading in human body, along with the corrosive body fluid, presents a great challenge for the practical use of biodegradable magnesium implants. In this study, a high purity magnesium (99.99wt.%) and two typical promising biodegradable magnesium alloys (binary Mg-1Ca and ternary Mg-2Zn-0.2Ca) were chosen as the experimental materials. Their dynamic mechanical performances were comparatively evaluated by carrying out fatigue tests in air and in simulated body fluid (SBF). The fatigue strengths of HP-Mg, Mg-1Ca and Mg-2Zn-0.2Ca were all around 90MPa in air, however, they decreased to 52MPa, 70MPa and 68MPa in SBF at 4×10(6)cycles, respectively. The fatigue cracks initiated from the microstructural defects when tested in air, but nucleated from surface corrosion pits when tested in SBF. Cyclic loading significantly increased the corrosion rates of all the experimental materials compared to that in static SBF. Moreover, based on our findings, the fatigue failure processes and interactions between material, corrosion and cyclic loading were systematically discussed.
  
  
  
  Fatigue strength and life are vital parameters to the design of metallic implant devices. For the corrosion fatigue of biomedical magnesium alloys, we reported the corrosion fatigue behavior of AZ91D and WE43 in SBF (Acta Biomaterialia, 6 (2010) 4605-4613), and till now there is no other reports to our knowledge. We spent 3years to finish the fatigue testing and get S-N curves for three more magnesium biomaterials, and our significant finding is that the fatigue strengths of HP-Mg, Mg-1Ca and Mg-2Zn-0.2Ca are all around 90MPa in air but 52MPa, 70MPa and 68MPa in SBF at 4×10(6)cycles, which will provide the first-hand data for the future magnesium implants design.
authors.affiliation: Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871, China.
authors.forename: Dong
authors.initials: D
authors.lastname: Bian
authors.affiliation: Center for Biomedical Materials and Tissue Engineering, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China.
authors.forename: Weirui
authors.initials: W
authors.lastname: Zhou
authors.affiliation: Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871, China.
authors.forename: Nan
authors.initials: N
authors.lastname: Li
authors.affiliation: Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871, China; Center for Biomedical Materials and Tissue Engineering, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China. Electronic address: yfzheng@pku.edu.cn.
authors.forename: Yufeng
authors.initials: Y
authors.lastname: Zheng
authors.affiliation: State Key Laboratory for Turbulence and Complex System, College of Engineering, Peking University, Beijing 100871, China. Electronic address: sunzhl@pku.edu.cn.
authors.forename: Zhili
authors.initials: Z
authors.lastname: Sun
mesh_terms: D000388:Air; D000497:Alloys / Q000737:chemistry*; D001672:Biocompatible Materials / Q000737:chemistry*; D001826:Body Fluids / Q000737:chemistry*; D003343:Corrosion; D006801:Humans; D008422:Materials Testing; D008670:Metals / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D013314:Stress, Mechanical; D013718:Tensile Strength; D014961:X-Ray Diffraction
chemical_list: D000497:Alloys; D001672:Biocompatible Materials; D008670:Metals
keywords: Biomedical magnesium alloy; Corrosion fatigue; Fatigue; Simulated body fluid