Fabrication, mechanical properties and in vitro degradation behavior of newly developed Zn-Ag alloys for degradable implant applications
Fabrication, mechanical properties and in vitro degradation behavior of newly developed Zn-Ag alloys for degradable implant applications
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DOI：
10.1016/j.msec.2017.04.023
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发表时间：
2017-08-01
影响因子：
7.9
通讯作者：
Vedani, M.
中科院分区：
文献类型：
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作者：
Sikora-Jasinska, M.;Mostaed, E.;Vedani, M.
锌和锌基合金已被认为是用于骨科植入物和心血管支架的极具前景的可生物降解材料，因为它们具有经过验证的生物相容性，更重要的是，与镁合金相比，其腐蚀速率较低。然而，纯锌的机械性能较差。在这项研究中，Ag 被用作一种有前途的合金元素，以提高 Zn 基体的机械性能及其生物相容性和抗菌性能。据此，我们设计了三种Ag含量范围为2.5至7.0 wt%的Zn-Ag合金，并研究了Ag含量对合金机械和腐蚀行为的影响。该合金采用铸造工艺研制，在410℃下均质化6h和12h，然后在250℃下热挤压，挤压比为14:1。通过在汉克改良溶液中进行电化学和静态浸没测试来评估降解行为。微观结构分析表明，热挤压显着减小了合金的晶粒尺寸。 Zn-7.0%Ag合金具有相当等轴且相当细化的显微组织，平均晶粒尺寸为1.5μm。室温拉伸试验表明，增加Ag含量可以稳定提高拉伸强度，同时不会显着影响拉伸塑性。 Zn-7.0%Ag 表现出较高的屈服强度和极限抗拉强度，分别为 236 MPa 和 287 MPa，这是由于挤压过程中晶粒细化和沿晶界析出的细 AgZn3 颗粒的高体积分数所致。在所有这些合金中，Zn-7.0%Ag 在较宽的应变速率范围内（从 5 x 10(-4) s(-1) 到 1.0 x 10(-2) s(-1)）表现出超塑性，为快速和/或什至在较低温度下利用成形工艺提供了可能性。此外，挤压合金的降解速度比纯锌稍快。 X 射线衍射结果显示降解表面上存在 ZnO 和 Zn(OH)(2)。此外，扫描电子显微镜成像显示，由于 AgZn3 颗粒的体积分数较高，因此 Ag 含量较高的合金的微电偶腐蚀更加明显。 (C) 2017 Elsevier B.V. 保留所有权利。
Zn and Zn-based alloys have been recognized as highly promising biodegradable materials for orthopedic implants and cardiovascular stents, due to their proved biocompatibility and, more importantly, lower corrosion rates compared to Mg, alloys. However, pure Zn has poor mechanical properties. In this study, Ag is used as a promising alloying element to improve the mechanical properties of the Zn matrix as well as its biocompatibility and antibacterial properties. Accordingly, we design three Zn-Ag alloys with Ag content ranging from 2.5 to 7.0 wt% and investigate the influence of the Ag content on mechanical and corrosion behavior of the alloys. The alloys are developed by casting process and homogenized at 410 degrees C for 6 h and 12 h, followed by hot extrusion at 250 degrees C with extrusion ratio of 14:1. Degradation behavior is assessed by electrochemical and static immersion tests in Hank's modified solution. Microstructural analysis reveals that hot extrusion significantly reduces the grain size of the alloys. Zn-7.0%Ag alloy shows a reasonably equiaxed and considerably refined microstructure with mean grain size of 1.5 mu m. Tensile tests at room temperature suggest that increasing the Ag content steadily enhances the tensile strength, while it does not affect the tensile ductility significantly. Zn-7.0%Ag shows high yield strength and ultimate tensile strength of 236 MPa and 287 MPa, respectively, which is due to the grain refinement and high volume fraction of fine AgZn3 particles precipitating along the grain boundaries during the extrusion process. Among all these alloys, Zn-7.0%Ag displayed superplasticity over a wide range of strain rates (from 5 x 10(-4) s(-1) to 1.0 x 10(-2) s(-1)) providing the possibility of exploiting forming processes at rapid rates and/or even at lower temperatures. In addition, extruded alloys exhibit slightly faster degradation rate than pure Zn. X-ray diffraction results show the presence of ZnO and Zn(OH)(2) on the degraded surfaces. Moreover, scanning electron microscopy imaging reveals that micro-galvanic corrosion is more pronounced on the alloys with higher Ag content due to the higher volume fraction of AgZn3 particles. (C) 2017 Elsevier B.V. All rights reserved.