[论文解读] Microstructure, mechanical properties, corrosion resistance and cytocompatibility of WE43 Mg alloy scaffolds fabricated by laser powder bed fusion for biomedical applications

M. Li, Felix Benn+7 more|arXiv (Cornell University)|Oct 8, 2020

Magnesium Alloys: Properties and Applications参考文献 42被引用 8

一句话总结

本研究探讨了通过激光粉末床熔融（LPBF）技术制备开放多孔WE43镁合金支架用于生物医学植入物，结果表明，杆径和后续热处理显著影响其显微组织、力学性能及耐腐蚀性。未经处理和固溶处理的支架腐蚀速率最低（2–3 mm/年），经等离子电解氧化（PEO）处理后进一步降低至约0.1 mm/年，且PEO涂层支架因生物相容性改善而实现了持续的细胞增殖。

ABSTRACT

Open-porous scaffolds of WE43 Mg alloy with a body-center cubic cell pattern were manufactured by laser powder bed fusion with different strut diameters. The geometry of the unit cells was adequately reproduced during additive manufacturing and the porosity within the struts was minimized. The microstructure of the scaffolds was modified by means of thermal solution and ageing heat treatments and was analysed in detail by means of X-ray microtomography, optical, scanning and transmission electron microscopy. Moreover, the corrosion rates and the mechanical properties of the scaffolds were measured as a function of the strut diameter and metallurgical condition. The microstructure of the as-printed scaffolds contained a mixture of Y-rich oxide particles and Rare Earth-rich intermetallic precipitates. The latter could be modified by heat treatments. The lowest corrosion rates of 2-3 mm/year were found in the as-printed and solution treated scaffolds and they could be reduced to ~0.1 mm/year by surface treatments using plasma electrolytic oxidation. The mechanical properties of the scaffolds improved with the strut diameter: the yield strength increased from 8 to 40 MPa and the elastic modulus improved from 0.2 to 0.8 GPa when the strut diameter increased from 275 μm to 800 μm. Nevertheless, the strength of the scaffolds without plasma electrolytic oxidation treatment decreased rapidly when immersed in simulated body fluid. In vitro biocompatibility tests showed surface treatments by plasma electrolytic oxidation were necessary to ensure cell proliferation in scaffolds with high surface-to-volume ratio.

研究动机与目标

• 通过激光粉末床熔融技术开发WE43镁合金支架，用于承重生物医学植入物。
• 研究杆径和热处理对显微组织与力学行为的影响。
• 在模拟体液中评估耐腐蚀性，并通过表面处理进行优化。
• 评估体外细胞相容性，并确定表面改性对细胞增殖的必要性。

提出的方法

• 采用WE43镁合金粉末，通过激光粉末床熔融技术制备具有体心立方晶胞的开放多孔支架。
• 通过改变杆径（275 µm至800 µm）研究尺寸依赖的力学与耐腐蚀响应。
• 采用固溶和时效热处理以调控显微组织和析出相。
• 利用X射线显微断层扫描、光学显微镜、扫描电镜和透射电镜分析显微组织与孔隙率。
• 在不同条件下（包括PEO表面处理）测量模拟体液（SBF）中的腐蚀速率。
• 在有无PEO涂层的支架上评估体外细胞相容性，以评估细胞增殖情况。

实验结果

研究问题

• RQ1 杆径如何影响LPBF制备的WE43镁合金支架的屈服强度和弹性模量？
• RQ2 固溶和时效热处理对未经处理的WE43镁合金支架显微组织和耐腐蚀性有何影响？
• RQ3 等离子电解氧化（PEO）处理能否显著降低WE43镁合金支架的腐蚀速率？
• RQ4 PEO涂层是否能实现高比表面积WE43镁合金支架上的持续细胞增殖？
• RQ5 热处理WE43镁合金支架中显微组织演变与力学性能之间的关系是什么？

主要发现

• 随着杆径从275 µm增加到800 µm，屈服强度由8 MPa提高至40 MPa，弹性模量由0.2 GPa提高至0.8 GPa。
• 未经处理的支架显微组织包含富含Y的氧化物颗粒和富含稀土元素的金属间化合物析出相，这些相在热处理后发生改变。
• 未经处理和固溶处理的支架腐蚀速率在2–3 mm/年之间，经等离子电解氧化（PEO）处理后降低至约0.1 mm/年。
• 未经PEO处理的支架在模拟体液中浸泡后表现出快速的强度退化，表明其在生理环境中的稳定性较差。
• PEO涂层支架支持持续的细胞增殖，证实对于高比表面积支架而言，表面处理对实现生物相容性至关重要。
• X射线显微断层扫描证实杆内孔隙率极低，表明LPBF制备的支架具有优异的几何保真度。