Abstract

Severe plastic deformation (SPD) is a popular group of techniques applied to achieve the nanostructuring of the metallic biomaterials and improvement of their mechanical characteristics. One of the most commonly used SPD methods is the high-pressure torsion (HPT) technique which enables the obtainment of the microstructure with small grains and high strength. In the present study, the influence of the plastic deformation and surface modification treatment on the tensile and corrosion properties of the Ti–13Nb–13Zr (wt%) alloy is investigated. In that purpose, the coarse-grained (CG) Ti–13Nb–13Zr (TNZ) alloy was subjected to the HPT processing by applying a pressure of 4.1 GPa with a rotational speed of 0.2 rpm and 5 revolutions at room temperature to obtain the ultrafine-grained (UFG) microstructure. The alloy microstructure before and after HPT processing was analysed using the scanning electron microscopy (SEM) and the X-ray diffraction (XRD). The homogeneity of the UFG TNZ alloy was determined by microhardness testing and microscopic observations. The nanotubular oxide layer on the surface of the TNZ alloy, both in CG and UFG condition, was formed by electrochemical anodization in 1 M H₃PO₄ + NaF electrolyte for 90 min. SEM analysis was used to characterise the morphology of the anodized surfaces, while energy dispersive spectroscopy was applied to determine the chemical composition of the nanostructured layers formed at the alloy surfaces. Mechanical properties of the TNZ alloy, before and after HPT processing and electrochemical anodization, were determined by tensile testing. After tensile testing, the fractographic analysis was conducted to identify the fracture mechanisms. The potentiodynamic polarization technique was used to determine the corrosion resistance of the alloy before and after plastic deformation and surface modification treatment. The obtained results showed that the alloy is reasonably homogeneous after the HPT processing. The XRD analyses reviled the presence of α′ and β phases in the CG TNZ alloy microstructure, while the additional ω phase was detected in the microstructure of the UFG TNZ alloy. The HPT obtained alloy exhibits higher hardness and improved tensile properties than the alloy in the as-received CG condition, while the electrochemical anodization leads to a decrease of its mechanical properties. Both CG and UFG alloys show excellent corrosion stability in Ringer’s solution. Moreover, electrochemical anodization leads to a decrease or an increase of the corrosion resistance of these materials, depending on the morphology of the formed nanotubular surface layers. The results indicate that the anodized CG TNZ alloy is characterized by a lower modulus of elasticity and better corrosion resistance properties than the anodized UFG TNZ alloy.

Graphic Abstract

中文翻译：

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高压扭弯获得的阳极氧化超细晶粒Ti-13Nb-13Zr生物医学合金的拉伸和腐蚀性能

摘要

严重塑性变形（SPD）是一组受欢迎的技术，可用于实现金属生物材料的纳米结构和改善其机械特性。最常用的SPD方法之一是高压扭转（HPT）技术，该技术可实现具有小晶粒和高强度的显微组织。在本研究中，研究了塑性变形和表面改性处理对Ti-13Nb-13Zr（wt％）合金的拉伸和腐蚀性能的影响。为此，通过在室温下施加4.1 GPa的压力，0.2 rpm的转速和5转的转数，对粗晶粒（CG）Ti-13Nb-13Zr（TNZ）合金进行HPT处理，以获得超细粉（UFG）晶粒组织。使用扫描电子显微镜（SEM）和X射线衍射（XRD）分析HPT加工前后的合金显微组织。UFG TNZ合金的均质性是通过显微硬度测试和显微镜观察确定的。通过在1 MH下进行电化学阳极氧化，在CG和UFG条件下，在TNZ合金表面上形成了纳米管氧化物层₃ PO ₄ + NaF电解质90分钟。SEM分析用于表征阳极氧化表面的形貌，而能量分散光谱则用于确定在合金表面形成的纳米结构层的化学组成。通过拉伸测试确定了HPT加工和电化学阳极氧化前后的TNZ合金的机械性能。拉伸测试后，进行了形貌分析，以确定断裂机理。电位动力学极化技术用于确定合金在塑性变形和表面改性处理之前和之后的耐腐蚀性。所得结果表明，HPT处理后的合金相当均匀。XRD分析表明，在CG TNZ合金的微观结构中存在α'和β相，而在UFG TNZ合金的微观结构中检测到了额外的ω相。所获得的HPT合金比在CG条件下的合金具有更高的硬度和改善的拉伸性能，而电化学阳极氧化导致其机械性能下降。CG和UFG合金在林格氏溶液中均具有出色的腐蚀稳定性。此外，取决于形成的纳米管表面层的形态，电化学阳极氧化导致这些材料的抗腐蚀性降低或增加。结果表明，与阳极氧化的UFG TNZ合金相比，阳极氧化的CG TNZ合金具有较低的弹性模量和更好的耐腐蚀性。而在UFG TNZ合金的显微组织中检测到额外的ω相。所获得的HPT合金比在CG条件下的合金具有更高的硬度和改善的拉伸性能，而电化学阳极氧化导致其机械性能下降。CG和UFG合金在林格氏溶液中均具有出色的腐蚀稳定性。此外，取决于形成的纳米管表面层的形态，电化学阳极氧化导致这些材料的抗腐蚀性降低或增加。结果表明，与阳极氧化的UFG TNZ合金相比，阳极氧化的CG TNZ合金具有较低的弹性模量和更好的耐腐蚀性。而在UFG TNZ合金的显微组织中检测到额外的ω相。所获得的HPT合金比在CG条件下的合金具有更高的硬度和改善的拉伸性能，而电化学阳极氧化导致其机械性能下降。CG和UFG合金在林格氏溶液中均具有出色的腐蚀稳定性。此外，取决于形成的纳米管表面层的形态，电化学阳极氧化导致这些材料的抗腐蚀性降低或增加。结果表明，与阳极氧化的UFG TNZ合金相比，阳极氧化的CG TNZ合金具有较低的弹性模量和更好的耐腐蚀性。所获得的HPT合金比在CG条件下的合金具有更高的硬度和改善的拉伸性能，而电化学阳极氧化导致其机械性能下降。CG和UFG合金在林格氏溶液中均具有出色的腐蚀稳定性。此外，取决于形成的纳米管表面层的形态，电化学阳极氧化导致这些材料的抗腐蚀性降低或增加。结果表明，与阳极氧化的UFG TNZ合金相比，阳极氧化的CG TNZ合金具有较低的弹性模量和更好的耐腐蚀性。所获得的HPT合金比在CG条件下的合金具有更高的硬度和改善的拉伸性能，而电化学阳极氧化导致其机械性能下降。CG和UFG合金在林格氏溶液中均具有出色的腐蚀稳定性。此外，取决于形成的纳米管表面层的形态，电化学阳极氧化导致这些材料的抗腐蚀性降低或增加。结果表明，与阳极氧化的UFG TNZ合金相比，阳极氧化的CG TNZ合金具有较低的弹性模量和更好的耐腐蚀性。CG和UFG合金在林格氏溶液中均具有出色的腐蚀稳定性。此外，取决于形成的纳米管表面层的形态，电化学阳极氧化导致这些材料的抗腐蚀性降低或增加。结果表明，与阳极氧化的UFG TNZ合金相比，阳极氧化的CG TNZ合金具有较低的弹性模量和更好的耐腐蚀性。CG和UFG合金在林格氏溶液中均具有出色的腐蚀稳定性。此外，取决于形成的纳米管表面层的形态，电化学阳极氧化导致这些材料的抗腐蚀性降低或增加。结果表明，与UFG TNZ阳极氧化相比，阳极氧化CG TNZ合金具有较低的弹性模量和更好的耐腐蚀性。

图形摘要