具有SiC纤维增强孔壁和桥联结构层状多孔钛合金的构建及复合强化机制

Lamellar porous titanium alloys with high porosity are becoming one of the candidates of bone implant biomaterials. Lamellar pores in titanium alloys is not only favored to reduce the “stress shielding” effect associated with mismatch of modulus, but also helpful to improve the biocompatibility due to the similarity with pore structure of natural bones. However, the low strength under quasi-static and dynamic compression has limited the application of lamellar porous titanium alloys with high porosity. Based on the interaction among alloy powders, short fibers and ice front, herein we fabricate SiC fiber/Ti6Al4V alloys lamellar porous materials with fiber reinforced pore wall and fiber translamella structure through by directionally freeze casting and vacuum sintering. The effects of fiber content, aspect ratio, freeze velocity and sintering temperature on the lamellar structure, translamella density and interfacial characteristics will be studied. The formation and controlling mechanism of fiber reinforced pore wall and translamella structure will be investigated by analyzing the rejection and engulfment of short fibers by the ice front. The project will study the quasi-static and dynamic compressive properties of SiC fiber/Ti6Al4V alloys lamellar porous materials. Finally, the combined strengthening mechanism of fiber reinforced pore wall and translamella structure will be clarified. The results of this project are beneficial to provide new idea and technique for designing of porous materials with high porosity. Moreover, they can develop the theoretical and application system of porous metals fabricated by freeze casting.

高孔隙率层状多孔钛合金作为骨植入材料理想的候选材料之一，具有与自然骨相似的孔结构和较好的生物相容性，能减小由于模量不匹配导致的“应力屏蔽”效应，但也存在准静态和动态压缩强度低的问题。本项目拟基于冷冻干燥技术中固-液界面与合金粉末和短纤维的交互作用，设计并构建具有“纤维增强孔壁结构”和“纤维桥联结构”复合强化方式的SiC纤维/Ti6Al4V合金层状多孔材料，研究短纤维含量、长径比、冷冻速率和烧结温度等对层状结构、纤维桥联密度和界面特征的影响，探究冰晶生长过程中短纤维被固-液界面排出或吞噬的热-动力学规律，阐明纤维增强孔壁和桥联结构的形成和控制机理，研究层状多孔材料的准静态和动态压缩力学性能，分析压缩变形方式和断裂机制，揭示纤维增强孔壁和桥联结构对层状多孔材料力学性能的复合强化机制，为优化设计新型兼具高孔隙率和高强度的层状多孔材料提供新的思路和技术，同时拓展冷冻干燥技术的理论和应用体系。

层状多孔钛合金具有与骨相似的孔结构和较好的生物相容性，能减小由于模量不匹配导致的“应力屏蔽”效应，是骨植入材料理想的候选材料之一。针对高孔隙率层状多孔钛合金强化方式单一和强度低的问题，本项目基于冷冻干燥技术中固-液界面与合金粉末和短纤维的交互作用，设计并构建了具有“纤维增强孔壁结构”和“纤维桥联结构”复合强化方式的SiC纤维/Ti6Al4V合金层状多孔材料，研究了纤维含量、长径比和冷冻温度等对层状结构、界面特征、纤维增强孔壁和桥联结构的影响，探究了冰晶生长过程中短纤维被固-液界面排出或吞噬的热-动力学规律，阐明了纤维增强孔壁和桥联结构的形成和控制机理，研究了层状多孔材料的压缩力学性能，分析了变形方式和断裂机制，揭示了纤维增强孔壁和桥联结构对层状多孔材料力学性能的复合强化机制。研究了Ti6Al4V合金粉末固含量、冷冻温度对多孔材料层状孔结构的影响规律。结果表明，随着Ti6Al4V合金粉末固含量的增加，多孔材料的孔隙率降低，结构波长有所升高。对于同一固含量的多孔材料，沿冷冻方向孔结构呈梯度分布，越远离冷源，结构波长越大。随着冷冻温度的降低，多孔Ti6Al4V合金的孔隙率和结构波长随之降低。探究了冷冻过程中，纤维与固-液界面前沿的相互作用规律。由于纤维的各向异性，纤维在固-液界面前沿受到陶瓷浆料的粘滞力增大，纤维与固-液界面的夹角越小，粘滞力越大。纤维易于被固-液界面“吞噬”形成纤维桥联结构。随着SiC纤维的添加，多孔材料的桥联密度提高，孔隙率升高，结构波长增加。无机SiC纤维的引入显著提高了多孔材料的抗压强度及模量，但过量的SiC纤维会导致第二相生成的增多，从而降低多孔材料的力学性能。项目的研究成果可以为优化设计新型兼具高孔隙率和高强度的层状多孔材料提供新的思路和技术，同时可以拓展冷冻干燥技术的理论和应用体系。项目研究过程中，以第一作者或通讯作者发表了SCI论文10篇，申请或授权了国家发明专利5项，培养了硕士研究生4名，1项专利实现了成果转化。