【作者】 毛丽贺；

【导师】 王玉林；

【作者基本信息】 天津大学 ， 材料学， 2009， 博士

【摘要】 医用镁合金作为可吸收的植入材料具有巨大的发展潜力。本课题通过从生物学和冶金学两方面考察相关元素的作用,优选出了钙和锌作为合金元素,并在查阅大量文献的基础上,对镁钙锌合金的成分进行了设计,熔炼出了两种相同钙含量、不同锌含量的镁钙锌合金,即Mg-1.0 wt.%Ca-0.3 wt.%Zn和Mg-1.0 wt.%Ca-1.0 wt.%Zn。随后对其进行热处理和离子注入表面改性,并对合金元素强化机制及合金在模拟体液（SBF）中的腐蚀行为进行了研究。通过和纯镁、镁铝锌合金（AZ91）的性能对比,评价了镁钙锌合金作为硬组织植入物的优势和特点。实验结果表明,Ca和Zn能够细化镁合金的组织,在合金中形成二元相Mg₂Ca和三元相Mg₆Ca₂Zn₃,合金经过人工时效后,Mg₆Ca₂Zn₃相弥散析出。合金的压缩和弯曲性能测试结果表明,随锌含量的增加,合金的弯曲模量、抗弯强度、弯曲断裂挠度增大,压缩模量、抗压强度、压缩屈服点等略有降低。应用高能真空金属离子注入技术将Ti离子和Zr离子在110 keV的能量下,分别以5×1016 ions/cm²、1.0×10¹⁷ ions/cm²、1.5×10¹⁷ ions/cm²三种不同剂量注入到纯镁、镁钙锌合金和AZ91合金的表面。EDS和XPS分析结果表明,离子注入后,合金表面的元素含量随着注入剂量的增加而增大,注入的Ti离子在合金表面形成了TiO₂层。离子注入前后表面纳米压痕测试的结果还证实,离子的注入使合金表面硬度和模量均有一定程度的提高。三电极体系测试结果表明,未经离子注入的镁钙锌合金的极化阻力远高于纯镁,但低于AZ91;Zr离子注入后合金的极化阻力均高于Ti离子注入的合金。镁钙锌和AZ91合金在SBF中的浸泡实验结果表明,经过相同时间的浸泡,AZ91的质量损失速率较低,其次为锌含量为1.0 wt.%的镁钙锌合金;离子注入后合金的腐蚀速率均显著降低,其中锌含量为1.0 wt.%的镁钙锌合金的腐蚀速率最低,其耐腐蚀性优于AZ91。镁钙锌合金与AZ91表面均有羟基磷灰石生成,具有较好的生物活性。锌含量为1.0 wt.%的镁钙锌合金经离子注入后在SBF中表现最稳定,同时具有合适的弯曲和压缩力学性能,是性能最佳的合金。这种合金经离子注入后,其体内植入物制品表面积最高可达240 cm²,能够满足一般体内植入物的表面积要求。更多还原

【Abstract】 Biocompatible magnesium alloys offer great potential as absorbable implant materials. In this study, biocompatable Ca and Zn elements were selected as the alloying element by investigating the effect of certain elements on biology and metallurgy. On the basis of numerous reading of literatures, the alloys with same component of Ca and different component of Zn were designed and prepared. Then heat treatment and surface modification by implanting Ti and Zr ions were carried out on the alloys. The mechanical properties and corrosion resistance of alloys in SBF were investigated. The superiority and characteristic of Mg-Ca-Zn alloys were estimated by comparing with pure Mg and AZ91 magnesium alloy.The results showed that Ca and Zn can refine the magnesium alloy and formed Binary phase Mg₂Ca and ternary phase Mg₆Ca₂Zn₃ in the microstructure of the alloys. After artificial aging, the Mg₆Ca₂Zn₃ precipitates inside of the grain. The bending and compression test showed that the bending modulus, bending intensity, rupture flexibility were improved as the Ca content increasing. At the same time, compression modulus, compression intensity and yield point decreased.Under the 110 keV energy, the Ti ions and Zr ions were implanted into the pure magnesium, Mg-Ca-Zn and AZ91 alloys surface respectively at the dose of 5×1016 ions/cm², 1.0×10¹⁷ ions/cm², 1.5×10¹⁷ the ions/cm² by Metal Vapour Vacuum Arc （MEVVA） ion implantation device. EDS and the XPS analysis results indicated that the alloy surface element content increased with the implantation dose grows after ion implantation. The TiO2 layer has been formed in the alloy surface implanted Ti. The superficial nanometer indentation test result also confirmed that the ion implantation caused the alloy surface hardness and the modulus enhanced at a certain degree.Three electrode system tests indicated that the polarization resistance of the Mg-Ca-Zn alloy by ion implantation was far higher than the pure magnesium, but lower than AZ91; the polarization resistance of the alloys implanted Zr was higher than implanted Ti.The results that Mg-Ca-Zn alloy and the AZ91 immersed in SBF for 72 h finally indicated that in the same time, among the four alloys unimplantation, the AZ91 corrosion rate was the lowest, next for alloyⅡwith Zn content of 1.0 wt.%. The corrosion rate of alloys was reduced by ion implantation. The corrosion rate of alloyⅡwas the lowest and its corrosion resistance had surpassed AZ91. The resulted alloy immersed in SBF indicated that anti-corrosive performance of the alloy was enhanced by ion implantation. Ion implantation can speed up the solution alkalize, thus slowed down the corrosion of the alloys.The alloyⅡwith Zn content of 1.0 wt.% behaved stably in SBF after ion implantation. Simultaneously, it had appropriate bending and compression mechanical performance. The max surface area of in vivo implant of this alloy after ion implantation was possible to reach 240 cm2, which can satisfy the request of implants in vivo.更多还原