Ti_2AlNb-Ag-TiB复合材料宽温域润滑性能与力学性能协同调控机制研究

The Ti_2AlNb matrix composites which are one of the most important high-temperature structural materials have been receiving much attention as candidate materials in aero-engines applications. The poor continuous lubricating, the mismatch of the lubricating properties and mechanical behavior of the Ti_2AlNb matrix composites at wide temperature range are two main key fundamental technological problems for its application in the motion pair of aero-engines. For this technology, clarifying the coordinately control mechanism of lubricating properties and mechanical behaviors is the key to successful application of the Ti_2AlNb matrix composites. However, investigations on revealing the behaviors and underlying mechanisms of the relevant processes conducted by researchers are still inadequate. Towards solving these problems, this project is to study the self-lubricating properties of the Ti_2AlNb-Ag-TiB composites at wide temperature range. The inherent relationships between the characteristics of the surface lubrication film and the tribological performance will be made clear at the formation conditions and inter-acting mechanism of the frictional layer. The self-lubricating mechanisms of the composites in different temperature regimes are to be revealed. The corresponding self-lubricating theoretical models are also established. In addition, the researches on effect different contents of the lubricating phase, reinforced phase, and inter-acting on mechanical properties of the composites are conducted, the corresponding relationship between performance and structural behavior is also established. The ultimate goal is to achieve harmonization and integration of excellent tribological properties and high mechanical performances. Thereby, this project establishes the theoretical foundation for the engineering application of the Ti_2AlNb matrix self-lubricating composites.

Ti_2AlNb基复合材料是航空发动机重要的高温结构材料之一，然而该材料的宽温域连续润滑性差以及润滑性能与力学性能不匹配问题是限制该材料在航空发动机高温运动副中应用的两个关键基础问题，而明晰润滑性能与力学性能的协同调控机制是该材料成功应用的关键，但目前对此研究尚不充分。鉴于此，本项目以Ti_2AlNb-Ag-TiB复合材料为研究对象，首先，探讨其宽温域下的自润滑特性，重点从摩擦层梯度结构的形成条件和作用机制阐明摩擦表面润滑膜的特征及其与摩擦学性能之间的关联，并揭示复合材料不同温域的自润滑机理，建立相应的自润滑理论模型；此外，还研究不同含量的润滑相、增强相及其协同作用对复合材料力学性能的影响规律和其作用机制，并建立相应的构性关系，进而实现优异摩擦学性能和较高力学性能的协调统一，为Ti_2AlNb基复合材料的工程化应用奠定理论基础。

TiAl系金属间化合物与传统钛合金相比，具有更高的比强度、良好的抗氧化性和更好的抗高温蠕变性能，成为钛合金的研究热点，但塑性差限制了其广泛应用。TiAl合金中添加Nb元素可以在不降低材料综合性能前提下，可以改善合金可加工性，提高塑性，尤其是对蠕变性能具有较大提高。目前，Ti2AlNb基合金做为航空航天发动机高温部件使用时，存在耐磨性不足、强度低、高温持久性差等问题，发展Ti2AlNb基复合材料可以充分提高Ti2AlNb基合金的应用潜力，拓展其未来在航空航天等领域更进一步应用。本项目从Ti2AlNb基合金出发，探究了机械合金化及粉末冶金对Ti2AlNb基合金显微组织与力学性能的影响规律，在此基础上，通过添加软金属Ag改善合金的耐磨性能，为了不降低合金的力学性能，在获得最优Ti2AlNb/Ag基复合材料的基础上，通过添加TiB提升复合材料的力学性能，通过调节增强相与润滑相的比例，最终实现该合金宽温域自润滑性能与力学性能的协调统一。