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ABSTRACT: Magnesium alloys are promising candidate materials for cardiovascular stents due to their good biocompatibility and degradation properties in the human body. However, in vivo tests also show that improvement in their mechanical properties and corrosion resistance is necessary before wide application. In this study, cyclic extrusion compression (CEC) was used to enhance the mechanical properties and corrosion resistance of Mg-Zn-Y-Nd alloy. The results show that the grain size was greatly refined to 1 μm after CEC treatment. The second phase distributed along the grain boundaries with grid shape and nano-sized particles uniformly distributed in grains. The elongation (δ), ultimate tensile strength (UTS) and yield strength (YS) of the CEC treatment samples were 30.2%, 303 MPa and 185 MPa respectively. The CEC treated samples showed homogeneous corrosion because of the grain refinement and the homogeneous distribution of nano-sized second phase. The corrosion current density of the alloy decreased from 2.8×10(-4) A/cm(2) to 6.6×10(-5) A/cm(2) after CEC treatment. Therefore, improved mechanical properties, uniform corrosion and reduced corrosion rate could be achieved by CEC.
Journal of the mechanical behavior of biomedical materials. 04/2012; 8:1-7.
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ABSTRACT: In present paper, an in vivo study was carried out on uncoated and calcium-deficient hydroxyapatite (Ca-def HA) coated Mg-Zn-Ca alloy to investigate the effect of Ca-def HA coating on the degradation behavior and bone response of magnesium substrate. Magnesium alloy rods were implanted into rabbit femora and evaluated during 24 weeks implantation. The characterization of both implants indicates that in vivo degradation of the Ca-def HA coating and magnesium substrate occurs almost simultaneously, and in vivo valid life of the coating is about 8 weeks, after that the degradation rate of the coated implants increases obviously. The main reasons for the Ca-def HA coating degradation can be attributed to its reaction with body fluid and the substitution of Mg(2+) ions in Ca-def HA. Histopathological examinations show that the Ca-def HA coating has good osteoconductivity and is in favor of the formation of more new bone on the surface of magnesium alloy. So the Ca-def HA coating could not only slow down in vivo degradation of magnesium alloy but also improve its bone response.
Colloids and surfaces. B, Biointerfaces 07/2011; 88(1):254-9. · 2.60 Impact Factor
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Shaokang Guan,
Junhua Hu,
Liguo Wang, Shijie Zhu,
Huanxin Wang,
Jun Wang,
Wen Li,
Zhenwei Ren,
Shuai Chen,
Erchao Meng,
Junheng Gao,
Shusen Hou,
Bin Wang,
Binbin Che
01/2011; , ISBN: 978-953-307-972-1
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ABSTRACT: Magnesium alloy stent has been employed in animal and clinical experiment in recent years. It has been verified to be biocompatible and degradable due to corrosion after being implanted into blood vessel. Mg-Y-Gd-Nd alloy is usually used to construct an absorbable magnesium alloy stent. However, the corrosion resistant of as cast Mg-Y-Gd-Nd alloy is poor relatively and the control of corrosion rate is difficult. Aiming at the requirement of endovascular stent in clinic, a new biomedical Mg-Zn-Y-Nd alloy with low Zn and Y content (Zn/Y atom ratio 6) was designed, which exists quasicrystals to improve its corrosion resistance. Additionally, sub-rapid solidification processing was applied for preparation of corrosion-resisting Mg-Zn-Y-Nd and Mg-Y-Gd-Nd alloys. Compared with the as cast sample, the corrosion behavior of alloys in dynamic simulated body fluid (SBF) (the speed of body fluid: 16 ml/800 ml min(-1)) was investigated. The results show that as sub-rapid solidification Mg-Zn-Y-Nd alloy has the better corrosion resistance in dynamic SBF due to grain refinement and fine dispersion distribution of the quasicrystals and intermetallic compounds in alpha-Mg matrix. In the as cast sample, both Mg-Zn-Y-Nd and Mg-Y-Gd-Nd alloys exhibit poor corrosion resistance. Mg-Zn-Y-Nd alloy by sub-rapid solidification processing provides excellent corrosion resistance in dynamic SBF, which open a new window for biomedical materials design, especially for vascular stent application.
Journal of Materials Science Materials in Medicine 03/2010; 21(7):2001-8. · 2.32 Impact Factor
