可控降解医用镁基表面LSP/MAO功能化微结构重构及腐蚀疲劳行为评价

Biodegradable magnesium-based materials as novel human implants is one of a forefront topic in medical science due to outstanding biocompatibility, excellent mechanical properties, spontaneous degradation, and the density and elastic modulus close to bone tissue. Unfortunately, the degradation rate of magnesium-based materials is too quick in the physiological environment to keep mechanical integrity before the diseased or damaged bone tissue healed, which restricted their clinical application as implants. However, the researches about controlling degradation rate and improving anticorrosion-fatigue of the materials in the physiological environment have seldom been reported. The overall goal in this project is to investigate the degradation process and corrosion fatigue behavior for surface modified Mg alloys through experiment, and to develop a theoretical model predicting corrosion fatigue life. . The main tasks in this project are as follows. . I. Reconstruction of functionalized surface microstructure. Through laser shot peening (LSP) and micro arc oxidation (MAO) technologies a new composite called nano-bioactive ceramic layer covering magnesium is fabricated which has characteristics such as multiscale, multilayer and functionalization. The effect of preparation process on microstructure and properties of the new layer will be investigated. The formation mechanism of the LSP/MAO functional reconstruction layer will be clarified.. II. Controllable degradation of LSP/MAO functional reconstruction layer. The degradation behavior of the LSP/MAO functional reconstruction layer will be investigated by means of immersion tests and electrochemical impedance spectroscopy (EIS) in the simulated body fluid (SBF). The degradation mechanism of the LSP/MAO functional reconstruction layer will be confirmed through electrochemical theories and modern microstructure testing technology. A computer simulation model will be established for technique optimization and controllable degradation of the functional reconstruction layer through GA-BP Neural Network. . III. Corrosion fatigue of surface modified magnesium alloy. The corrosion fatigue behavior of the substrate and LSP/MAO modified samples will be investigated by means of fatigue tests in SBF. The mechanical -electrochemical interaction effect during the corrosion fatigue will be analyzed, and the failure mechanism of the LSP/MAO functional reconstruction layer will be investigated considering the couple of corrosion and load. It will be revealed why LAS/MAO functional reconstruction layer has anti-corrosion and anti-fatigue properties.. IV. Prediction model of corrosion fatigue life. Based on theories of cumulative fatigue damage and fracture mechanics, a modified corrosion fatigue model will be established considering the critical surface method and crack closure effect. . This project plays an important role in development and application of magnesium-based implant materials, and promotes researches of corrosion theory and corrosion fatigue fracture control in magnesium alloy. Therefore, the research in this project not only has an important academic value but also an application prospect in medical science.

可降解镁基材料作为新型人体植入物是医学研究的前沿。如何控制其降解速率及抗腐蚀疲劳方面的研究几乎是空白。本项目采用激光冲击喷丸和微弧氧化复合改性技术，在镁合金表面构建多尺度、多层次、功能化的纳米晶-生物活性陶瓷重构层。在模拟生理体液中进行浸泡、电化学及腐蚀疲劳试验。结合电化学理论及现代微观测试方法，调查LSP/MAO重构层的降解行为，阐明重构层的降解调控机理；采用GA-BP神经网络技术，建立重构层工艺优化/可控降解的计算机仿真模型。分析腐蚀疲劳过程中的力学-电化学效应，探讨LSP/MAO重构层在介质和载荷耦合作用下的失效机制；揭示重构层抗腐蚀和疲劳双重效应的原因。基于累计疲劳损伤理论和断裂力学理论，建立改性镁基材料的腐蚀疲劳寿命预测模型。该研究对新型医用可控降解镁基植入材料的制备和应用技术、镁合金防腐理论和腐蚀疲劳断裂控制的发展产生重要的推动作用。研究成果具有重要学术价值和医学应用前

采用镁基材料制作可降解植入器件，修复或替代受损硬组织具有巨大的优势和应用前景，但是，其在生理电解质环境下过快的降解速率限制了临床应用。如何控制镁基植入器件的降解速率及抗腐蚀疲劳方面的研究几乎是空白。本项目采用激光冲击喷丸（LSP）和微弧氧化（MAO）复合改性技术，在镁合金表面构建了多尺度、多层次、功能化的纳米晶-生物活性陶瓷重构层，赋予了镁基植入体生物活性、生物相容性、耐腐蚀和长疲劳寿命等人体环境所要求的综合服役性能。以典型镁合金ZK60、AZ80为研究对象，在材料表面分别制备了MAO和LSP单一改性层以及LSP/MAO复合改性层，在模拟生理体液中进行了短期和长期浸泡试验、电化学测试、应力腐蚀及腐蚀疲劳试验。结合电化学理论及微观结构分析，调查了LSP/MAO重构层的腐蚀和降解行为，阐明了重构层的降解可调控机理。通过电化学阻抗谱演化，分析了腐蚀过程中的力学-电化学效应，探明了不同改性层在介质和载荷耦合作用下的失效机制，揭示了LSP/MAO重构层抗腐蚀和疲劳双重效应的原因。提出了修正的能量基疲劳寿命预测模型，其对改性镁合金不同加载条件下腐蚀疲劳寿命的预测精度高于传统的模型。该研究对新型医用降解镁基植入材料的制备和应用技术、镁合金防腐理论和腐蚀疲劳断裂控制的发展产生重要的推动作用。研究成果具有重要学术价值和医学应用前景。