Creation of super elastic and plastic-functional titanium materials with low elastic modulus for biomedical applications by controlling nanostructure

钛合金作为一种具有与骨相似模量的高生物相容性材料而备受关注。因此，有许多钛合金。目前已开发用于生物医学应用。特别是以低杨氏模量和高可加工性为目标，采用DV-Xα簇法设计的β型Ti-29Nb-13Ta-4.6Zr合金，是一种无毒、无过敏的生物医用钛合金。据报道，该合金具有生物材料所需的优异性能。近年来，有报道称Ti-Nb-Ta-Zr系合金在拉伸载荷下的应力-应变曲线行为与TiNi合金等超弹性合金的应力-应变曲线行为基本一致，具有很高的表现出超弹性的可能性，并已投入实际应用。然而，合金元素对Ti-Nb-Ta-Zr体系各项性能影响的报道较少，包括Ti-29Nb-13Ta-4.6Zr合金在内的合金数量较少。因此，本文从纳米/微观结构的角度研究了制备条件、热处理条件和合金元素对Ti-Nb-Ta-Zr系合金力学性能和拉伸变形行为的影响。粉末冶金法制备后的Ti-XNb-10Ta-5Zr合金的杨氏模量随铌含量的增加而减小。而含有15质量%、20质量%和25质量% Nb的共相Ti-XNb-10Ta-5Zr合金的杨氏模量呈现相反的趋势。Ti-25Nb-10Ta-5Zr合金的伸长率最高，这是因为多种变形机制同时起作用。在质量分数为20%和25质量分数Nb的Ti-XNb-10Ta-5Zr合金中，在拉伸加载-卸载过程中，亚稳co相发生应力诱导向马氏体相转变并发生逆转。这些类型的Ti-Nb-Ta-Zr系合金有望获得形状记忆效应和超弹性性能。Ti-30Nb-10Ta-5Zr合金的弹性变形行为不符合胡克定律。在这种情况下，最大弹性应变在2.9%左右。通过冷拔和热处理等热机械加工制备的直径分别为0.3和1.0 mm的Ti-29Nb-13Ta-4.6Zr合金丝在拉伸载荷下也表现出独特的双梯度弹性行为。两者的最大弹性应变分别为2.8和2.9%左右，比固溶处理的Ti-29Nb-13Ta-4.6Zr合金热锻棒材的弹性应变高2倍左右。因此，它有望应用于牙科和外科钢丝。本研究为设计具有低杨氏模量、形状记忆效应和超弹性等功能的新型医用钛合金提供了重要的指导。少

Titanium alloys have been getting an attention as high biocompatible material with a modulus similar to that of bone. Thus, a number of titanium alloys. have been currently developed for biomedical applications. Especially, the beta-type Ti-29Nb-13Ta-4.6Zr alloy, which has been designed by DV-Xα cluster method targeting a low Young's modulus and high workability, is a titanium alloy composed of non-toxic and allergy-free elements for biomedical applications. It has been reported that this alloy possesses excellent properties that are required for biomaterials. Recently, it has been reported that there is a high possibility for Ti-Nb-Ta-Zr system alloy to exhibit super elasticity because the behavior of stress-strain curve at tensile loading is nearly equal to that of super elastic alloys such as TiNi alloy, which has been already put into practical applications. However, the numbers of the reports on the effects of alloying elements on the various properties of the Ti-Nb-Ta-Zr system a … More lloys including the Ti-29Nb-13Ta-4.6Zr alloy are few. Therefore, the effects of conditions of fabrication and thermo-mechanical treatments, and alloying elements on the mechanical properties and tensile deformation behaviors of the Ti-Nb-Ta-Zr system alloys are investigated with relating to nano/micro-structures in this study.Young's moduli of the Ti-XNb-10Ta-5Zr alloys subjected to swaging after fabrication using power metallurgy method decrease with an increase in the Nb content. However, the Young's moduli of the Ti-XNb-10Ta-5Zr alloys with 15 mass%, 20 mass%, and 25 mass% Nb, which have co phase, exhibit a reverse trend. The Ti-25Nb-10Ta-5Zr alloy exhibits the greatest elongation among the other Ti-XNb-10Ta-5Zr alloys because multi deformation mechanisms act simultaneously. Stress-induced transformation of metastable co phase to martensite phase, and its reversion are recognized in the Ti-XNb-10Ta-5Zr alloys with 20 mass% and 25 mass% Nb at tensile loading-unloading. The shape memory effect and the super elastic property are expected to be achieved in these types of the Ti-Nb-Ta-Zr system alloys. The elastic deformation behavior of the Ti-30Nb-10Ta-5Zr alloy disobeys Hooke's law. In this case, the maximum elastic strain is around 2.9%.The Ti-29Nb-13Ta-4.6Zr alloy wires with diameters of 0.3 and 1.0 mm fabricated by thermo-mechanical processing including cold-drawing and heat treatment also show an unique elastic behavior with two gradients under tensile loading. Their maximum elastic strains are around 2.8 and 2.9%, respectively, which are around twice higher than that of the hot forged bar of the Ti-29Nb-13Ta-4.6Zr alloy subjected to a solution treatment. Therefore, it is highly expected to be applied to dental and surgical wires. From these results, in this study, an important guideline can be obtained for designing new titanium alloys for medical applications, which have the functionalities such as low Young's modulus, shape memory effect and super elasticity. Less