基于界面结构优化实现钛/β-钛合金多层复合材料强韧化的机制研究

Titanium has been extensively used in biomedical applications due to its high ductility, high corrosion resistance and good biocompatibility. However, as the heavy-load implants, pure Ti usually does not have matching modulus and strength with human bones. This proposal combines β-Ti alloy (Ti-15Mo) which has high strength and low modulus with pure Ti to fabricate the coarse-grained Ti/fine-grained β-Ti alloy laminated composite through spark plasma sintering, hot/cold rolling, and partial recrystallization annealing. It is expected that the composite with good interfacial structure could have excellent mechanical properties (high strength, high ductility, and low modulus). In this proposal, the effect of process parameters of sintering, rolling and annealing on the diffusion behavior at the Ti/ β-Ti alloy interface will be firstly studied. Then we will elucidate the relationship between processes and the interfacial structure to control the interfacial structure and investigate the influence of interfacial structure on the room-temperature tensile behavior and crack growth behavior. The strengthening and toughening mechanisms of laminated composite will be revealed theoretically by molecular dynamics simulation and experimentally by in-situ EBSD. The results of this project can serve as theoretical basis for fabrication, strengthening, and toughening of biomedical Ti/β-Ti laminated composite and reference to the understanding of the strengthening and toughening mechanisms of other metal/metal laminated composite.

纯钛具有优异的韧性、耐蚀性和生物相容性，被广泛应用于生物医用领域。然而，纯钛作为骨植入体时，存在强度及弹性模量与自然骨不能匹配的问题。本项目提出将高强度、低模量的β-钛合金(Ti-15Mo)与纯钛进行层状复合，采用放电等离子烧结、热／冷轧制及部分再结晶退火相结合的方法实现各金属层的致密化与界面结构的调控，最终制备出高强高韧低模量的粗晶钛／细晶β-钛合金多层复合材料。首先研究制备工艺对纯钛层与β-钛合金层界面扩散行为的影响规律，阐明制备工艺与界面结构之间的相关性；进而研究界面结构对材料室温拉伸行为与裂纹扩展行为的影响，运用分子动力学模拟与原位EBSD相结合的方法揭示界面层的增强增韧机制；最终建立制备工艺-界面结构-材料强韧化之间的关系模型。本项目研究结果可以为生物医用钛／β-钛合金多层复合材料的制备及强韧化提供理论支撑，并对金属基复合材料的强韧化研究具有重要的参考价值。

纯钛具有优异的韧性、耐蚀性和生物相容性，被广泛应用于生物医用领域。然而，纯钛作为骨植入体时，存在强度及弹性模量与自然骨不能匹配的问题。项目采用粉末冶金技术实现了高强度、低模量的β-钛合金与纯钛的层状复合，并通过热轧、冷轧、热处理等手段对复合材料组元层与界面结构进行有效调控，获得了高强高韧低模量的钛/β-钛合金多层复合材料。基于此，项目以Ti/Ti-15Mo层状复合材料为例，探明了Ti/β-Ti合金层状复合材料烧结过程中的致密化机制，获得了较优选的钛基层状复合材料的烧结温度区间。揭示了热力耦合作用下界面结构的演化规律，阐明了高强高硬连续扩散界面层对钛基层状复合材料塑性变形行为与裂纹扩展行为的影响机制。此外，项目依据β钛合金相转变温度的不同，开发两种高强韧低模量钛基层状复合材料的粉末冶金制备工艺。本项目形成的技术原型与研发的产品适用于生物医用骨科植入领域，可进一步促进高性能钛材的实用化进程。