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摘要最近，一组被称为口香糖金属的体心立方结构的β-Ti合金Ti-23Nb-0.7Ta-2Zr-O展现出多种优异的力学性能组合及其作为外科人工移植材料的潜在应用前景。比如，超高强度，超低的弹性模量，类似超弹性的弹性变形，类似超塑性的冷变形能力，Invar及Elinvar性能等等。此外，该口香糖合金所含元素都是无毒性元素，且其具有与人体骨骼相近的杨氏模量及良好的生物相容性，使其成为理想的生物医用材料。9846
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在应用前，对于Ti-23Nb-0.7Ta-2Zr-O合金的各项力学性能的研究都是必不可少的。本论文主要以粗晶和纳米晶Ti-23Nb-0.7Ta-2Zr-O合金为研究对象，对比研究它们在动态冲击和等静态加载下的性能异同。本论文用电弧熔炼法制备粗晶Ti-23Nb-0.7Ta-2Zr-O合金，再运用等径角挤压大塑性变形的方法制备出纳米晶Ti-23Nb-0.7Ta-2Zr-O合金，然后用等静态加载和动态冲击的方法处理粗晶和纳米晶样品并对比它们的性能异同，最后，运用扫描电镜（SEM）和光学金相分析技术研究它们在变形过程中的微观结构演化规律。主要结论如下：
1. 综合各样品的真应力应变曲线可知，大塑性变形（ECAP）对口香糖金属Ti-23Nb-0.7Ta-2Zr-O的强度没有太大影响。
2. Extrude Ti样品在经受一定应变速率的动态冲击时，若加载方向与原Extrude方向垂直，样品易断裂失效。
3. ECAP Ti样品在经受一定应变速率的动态冲击时，若加载方向与原Extrude方向垂直，样品易断裂失效。
4. 从未经载实验的样品的side view可观察到长条状的变形带及变形带之间的大晶粒，在高应变速率的动态冲击实验中，载荷垂直施加在这样的结构上，当变形带变形程度不一致时，变形带与变形带之间错动形成裂纹。
关键词 口香糖金属 等径角挤压 动态冲击
毕业设计说明书（论文）外文摘要
Title Mechanical properties and microstructural evolution of Ti-23Nb-0.7Ta-2Zr-O alloys
Abstract
Recently, a group of bcc structured β-Ti alloy called gum metal, Ti-23Nb-0.7Ta-2Zr-O, was discovered to have the excellent combination of comprehensive mechanical properties and biocompatibility for orthopedic implants，such as ultrahigh strength, ultralow elastic modulus, superelastic-like elastic deformation, superplastic-like cold workability, Invar property and Elinvar property. In addition, the young’s modulus similar to human bones, nontoxic elements and biocompatibility made the gum metal Ti-23Nb-0.7Ta-2Zr-O to be the ideal biomaterial for implant applications.
It is necessary to investigate the mechanical properties of Ti-23Nb-0.7Ta-2Zr-O before applications. In this dissertation, we comparably investigated the mechanical properties of coarse-grained and nano-grained Ti-23Nb-0.7Ta-2Zr-O.The coarse-grained Ti-23Nb-0.7Ta-2Zr-O was fabricated by vacuum arc melting, and the nano-grained samples were prepared by equal-channel angular pressing(ECAP). Comparison of differences and commonness of their mechanical properties was made after they have been quasi-static compressed and dynamic tested. At last, the microstructural evolution was researched and discussed via optic microscopy and SEM during the process of deformation. The main conclusions are listed below:
1. Equal-channel angular pressing has no substantial effect on the strength of gum metal.
2. The Extrude Ti sample is vulnerable to failure to failure, if the load direction is perpendicular to the extrusion direction.
3. The ECAP Ti sample is vulnerable to failure, if the load direction is perpendicular to the original extrusion direction.
4. When the strip-like structure, as we can see from the side views of the samples which have not experienced the dynamic test, was loaded perpendicularly those hear bands did not deform simultaneously, therefore crevices emerged from the unmatched deformation.
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