牙种植体用成分梯度β钛合金中微观塑性行为的协同变形机制

Medical beta titanium alloy is the preferred new type of artificial dental implant materials. The focus of research and development is to improve its biomechanical compatibility. The preparation of a gradient material with continuously varying composition is a new way to optimize the combination of strong plasticity and to simulate the natural gradient structure and function of the tooth. The interaction and transmission mechanism of various plastic deformation in gradient β-titanium alloy are the key factors affecting their overall performance. However, there is no clear understanding at present. In this project, binary Ti-Nb β-titanium alloy with different gradient composition was prepared by three-dimensional (3D) printing technology. The composition, phase and microstructure of the Ti-Nb β titanium alloy before and after deformation will be measured by synchrotron radiation X-ray diffraction analysis /X-ray fluorescence analysis(XRD / XRF) and high-throughput metallurgy techniques. In-situ Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) will be applied to study the microstructure evolution, defect behavior and deformation coordination mechanism at different scales, including nucleation of stress-induced phase transformation and mechanical twins, density and configuration evolution of dislocations, and the initiation and propagation of cracks. Based on macroscopic and microscopic mechanical properties, synergistic mechanism of "Twinning induced plasticity"(TWIP) and "Transformation induced plasticity" (TRIP) in different local regions of gradient β-titanium alloy will be studied in detail. The purpose of this project is to clarify the relationship among the distribution of composition and microstructure, deformation mechanism and mechanical properties of gradient β-titanium alloy, and to provide a scientific basis for the design and development of new dental implants.

Ti-Nb系β钛合金是首选的新型牙种植体材料，根据使役需求将其制备为成分和性能连续变化的梯度材料，不仅可以改善其生物力学相容性，而且更符合牙齿的天然梯度结构和功能。梯度材料中各层次间多种微观塑性行为的相互作用和传递机制是影响力学性能的关键因素，但目前缺乏清晰的认识。本项目通过增材制造技术制备出不同成分梯度的二元Ti-Nbβ钛合金；利用同步辐射X射线衍射/荧光光谱技术、共聚焦激光扫描显微镜等测定其变形前后的成分、相和组织分布；利用原位扫描和透射电镜多尺度的研究其在加载过程中的微结构演化和缺陷行为，具体涵盖应力诱发相变和机械孪晶的形核生长、位错的密度和组态演变、裂纹的萌生和扩展等；结合宏观和微观力学性能，阐明成分梯度β钛合金中“孪生诱发塑性”和“相变诱发塑性”的协同响应机制。本项目旨在揭示β钛合金中成分梯度、微观塑性行为、力学性能之间的关联关系，为新型牙种植体材料的设计开发提供科学依据。

项目通过增材制造直接激光沉积（DLD）技术制备出成分梯度二元Ti-Nb系β钛合金、TC4/TNTZO层状材料、以及Ti/TNTZO层状材料，采用原位电镜等表征手段，对变形过程中的微结构演化、位错运动、机械孪生和应力诱发相变进行表征，揭示成分梯度、组织分布和力学性能之间的关联关系，阐明变形过程中各成分层次之间微观塑性行为的相互协调和传递机制。取得主要结果如下：.通过DLD技术制备的成分梯度β钛合金力学性能优异。电镜原位拉伸分析表明，在变形初期，位错滑移被触发，晶界等明显应力集中的区域产生了应力诱发的αʺ马氏体相变和ω相变，同时出现了{332}<113>孪晶；随着变形量的增加，出现了孪晶板条粗化、穿晶界生长等现象；部分晶粒出现晶界变形、孪晶界扭曲等现象。合金中{332}<113>孪晶形成后互相交割起到了细化晶粒的作用，表现出较好的TWIP效应；αʺ马氏体相的形成对变形过程中的局部应力集中起到了松弛作用，表现出较好的TRIP效应；部分区域中出现的应力诱发ω相，进一步提高了合金的强度。在TWIP/TRIP协调变形与应力诱导ω相的双重耦合作用下，成分梯度合金表现出良好的强塑性结合。.通过DLD技术制备了高致密、无缺陷的TC4/TNTZO和Ti/TNTZO层状材料，界面表现出良好的冶金结合。两种层状材料在TNTZO层的胞状亚晶界处出现了大量细小针状α"马氏体。TC4层和Ti层由于合金元素含量的增加，组织明显细化。元素的扩散导致界面处出现了一定厚度的过渡层，存在大量晶界α相和针状马氏体。两种层状材料都具有较高的强度和较低的模量，变形过程中软/硬界面处累积的几何必须位错导致背应力强化，使得层状材料的强度较高，但界面处出现的针状马氏体导致TC4/TNTZO和Ti/TNTZO层状材料的塑性降低。.综上所述，DLD技术制备的成分梯度钛合金具有优异的力学性能和独特的微观塑性行为，可以为新型牙种植体材料的设计开发提供科学依据。以上研究结果发表SCI学术期刊论文15篇，授权4项专利，包括3篇JAC，3篇MC，JMST ,MSEA，金属学报等。

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