SLM成形金属骨骼修复体材料与结构双梯度过渡层基础研究

The metal bone implants have major advantages of good mechanical properties and processability. However, the prominent problems of low binding force of implant-bone-interface and weak osseointegation characteristic because of material difference will be met during clinical applications. This proposal proposes to form a double-gradient transition layer with a specific thickness, along with the features of Ti/HA composition and scaffold gradients on the end of metal implant connected with bone, by using selective laser melting (SLM) method. It changes the composition mutation interface of current coating techniques to the component gradually transition, which endows high binding strength due to the metal-ceramic metallurgical bonding of gradient layer, and improves the osseointegation characteristic because of the scaffold structure and bioactive HA composition.In this proposal we mainly research some fundamental issues for realizing the creative idea described above: to study metallurgical mechanism and fundamental process of SLM Ti/HA composite material; to reveal the coupling influence law of material-structure-performance of SLM double-gradient transition layer, and its modelling descriptions; to characterize the biomechanical property of double-gradient transition layer and to analyse its failure mechanism. The research is promising likely to get some original achievements including metallurgical mechanism of SLM composite materials, fundamental process and mechanical characteristic of selective laser melting gradient materials and scaffold structure. It will establish theory and technology foundation for the practicality of this creative idea, having important theoretical significance and engineering value.

金属骨骼修复体具有力学性能优异和易加工的突出优势，但由于材料相异性，修复中面临接触界面结合力低和骨整合能力差的突出问题。课题提出利用选区激光熔化（SLM）技术，将金属修复体与骨骼接触端成形为具有一定厚度的Ti/HA复合材料成分渐变且具有梯度多孔的双梯度过渡层。将现有涂层工艺的成分突变界面变为成分逐渐过渡模式，依靠过渡层中的金瓷冶金结合实现较高的修复结合强度，并利用多孔结构和生物活性HA成分增强骨整合能力。课题主要解决实现该创新思路的若干基础问题，重点研究SLM成形Ti/HA复合材料冶金机理及工艺基础，揭示SLM双梯度过渡层材料-结构-性能耦合影响规律及模型化表达，研究双梯度过渡层的生物力学性能与失效机制。研究有望在复合材料SLM冶金机理、梯度材料及多孔结构SLM工艺基础与力学特性方面获得原创性成果，为该创新思想的实用化奠定理论与技术基础，具有重要的理论意义与工程价值。

项目研究了激光选区熔化（SLM）增材制造原位制备Ti/HA材料与结构双梯度的新型过渡层，克服了金属基体与陶瓷涂层的材料突变、界面结合力低以及固体金属骨整合能力差的突出问题。阐明了SLM过程中Ti/HA复合材料的相成分演变规律，揭示了不同配比HA下Ti/HA复合材料的微观组织演变机理，制备的Ti/HA复合材料强度和模量分别达289 MPa和29 GPa，能匹配骨植入要求；建立了基于单元拓扑阵列的多孔结构优化方法，揭示了多类型单元拓扑下应力集中的现象及原因；原位制备了体积分数从5%变化至20%的梯度多孔结构，其支柱尺寸范围可从483 μm增加到905 μm，体积分数从7.97%增加至19.99%，建立了孔隙率与模量、强度之间的数学模型；成功制备了HA配比从0 wt. %到5 wt. %的Ti/HA准连续成分功能梯度材料，表征并评价了梯度材料的界面及形成机制，阐述了孔隙形成和裂纹形成机理；针对上述研究内容，在多材料SLM机构和工艺方面申请了发明专利7项，授权6项；在Acta Materialia、Scripta Materialia、Biomacromolecules等期刊上发表SCI论文27篇，荷兰学者在【Acta Biomaterialia, 65(2018):292】上引用了我们提出的不同单元拓扑多孔结构的性能影响，澳大利亚学者在【Acta Materialia, 126(2017):25】上引用了我们提出的基板预热能减小SLM零件开裂现象的观点，英国学者在【Mater. Sci. Eng. A, 667(2016):139】上引用我们提出的经过固溶热处理和时效处理SLM零件会产生析出相的观点，日本学者在【J. Mech. Behav. Biomed. Mater., 59(2016):446】上评价“Wei等的研究表明零件断裂起源于熔池边界，裂纹沿熔池边界扩展”，认同这影响了零件的各向异性；参加国际会议8次，作大会主题或邀请报告3次；成果“金属基复合材料的机构装备与成形一体化技术”获2016年湖北省科学技术发明一等奖（排2）。研究为金属骨植入体的材料和结构设计与制备提供了新思路，丰富了金属骨植入体个性化制造的理论基础。