近网络结构Ti2AlNp/TiAl基复合材料的制备与高温摩擦磨损特性研究

Ti2AlNp/TiAl composite is regarded as promising candidate materials with the excellent combination of plasticity and ductility, because Ti2AlN combines the properties of metals and ceramics. It is especially significant to investigate the properties of high temperature friction and wear of TiAl based composites used as heat resistance structural materials.However, there is no report on Ti2AlNp/TiAl composite with network reinforcement distribution and the systematic study and deep analysis on its high temperature tribological properties is scarce up to present.In the present application, the fabrication and synthesis mechanism of Ti2AlNp/TiAl composite with a novel near network reinforcement distribution are studied,and its phases, interfaces and microstructures of evolution as well as their evolution during the process of high temperature friction and wear are investigated; The effects of the oxidation state of surface and the parameters of frictional wear tests at high temperature on the property of wear resistance are studies, and their simulation models are established by using artificial neural network (ANN) to predict the friction and wear properties. The multiple-scale investigations on the friction and wear behavior and mechanism of Ti2AlNp/TiAl composite from macroscopic, mesoscopic, microstructure till to atomic and electric scale are carried out to reveal the mechanism of high temperature friction and wear of Ti2AlNp/TiAl composite. This research work can provide the theoretical and experimental basis for this kind of materials to be applicated at high temperature, moraover, it can enrich the theory of high-temperature tribology for TiAl matrix composites. In summary, the present research has important theoretical significance and practical value.

Ti2AlN具有金属和陶瓷的特性，Ti2AlNp/TiAl基复合材料有望具备较好的塑韧性。用作耐热结构件的TiAl基复合材料，其高温摩擦磨损性能是至关重要的。目前尚未见网络状分布Ti2AlNp/TiAl基复合材料的报道和对其高温摩擦学特性与机理的系统研究。本申请拟研究一种新型近网络状分布Ti2AlNp/TiAl基复合材料的制备与合成机理，研究该材料的相、界面、显微组织结构及其在高温摩擦磨损过程中的演化规律，研究高温下表面氧化状态和摩擦磨损条件对耐磨性的影响，建立组织结构参数、摩擦磨损参数与摩擦磨损性能的人工神经网络模型，实现摩擦磨损性能的预报，对复合材料的摩擦磨损行为和机制进行从宏观、介观、微观组织结构直至原子电子的多尺度研究，揭示复合材料高温下的摩擦磨损机制。此项研究可为该类复合材料的高温应用提供理论和实验依据，丰富TiAl基复合材料的高温摩擦学理论。本工作具有重要的理论意义和实用价值。

本项目研究了近网络结构Ti2AlN/TiAl复合材料的制备与组织结构演变，从宏观、微观至原子电子尺度对复合材料的摩擦磨损行为和机制进行了研究。采用渗氮的Ti(N)复合粉体和Al粉进行真空热压烧结，成功制备出颗粒状Ti2AlN增强相呈近网络结构分布在片层状TiAl相和Ti3Al相周围的TiAl基复合材料。复合材料的高温三点弯曲强度较全片层Ti-47Al合金有较大提高。复合材料中Ti2AlN颗粒多数呈近椭圆形和多边形，与基体TiAl相的界面多为Ti2AlN(10-13)/TiAl(111)非共格界面，第一性原理计算得到其界面粘附功为2.44 J/m2，界面键合是非均匀的，存在较强和较弱的原子作用区域；少数近六边形和短片状Ti2AlN相与基体相的界面主要是Ti22AlN(0001)/TiAl(111)共格界面，计算得到其界面粘附功较高，为2.99 J/m2，界面键合由Ti-Al共价键以及Ti-Ti金属键组成。与TiAl合金相比，在宽温域磨损条件下，15vol%Ti2AlN/TiAl复合材料具有更低的摩擦系数和磨损率。在高温条件下，复合材料磨损表面形成具有保护性的氧化物釉质层，对其高温摩擦磨损性能的提高起决定性作用。在恒定载荷和转速条件下，室温和600℃时，复合材料的磨损机制以犁削磨损为主；700℃时的磨损机制为犁削磨损和粘着磨损的混合磨损机制；800℃时以粘着磨损机制为主。转速恒定，随着载荷的增加，促进了复合材料磨损表面釉质层的形成，未引起磨损机制的变化。载荷恒定，随着转速的增加，复合材料的高温摩擦系数逐渐降低；但磨损机制未发生变化。经900℃预氧化的复合材料，在室温及600℃条件下，与未预氧化复合材料相比，表现出稳定的摩擦系数和较低的磨损率。预氧化层的存在增加了磨损过程中氧化物磨屑的数量，有利于复合材料磨损表面釉质层的形成。基于第二近邻修正型嵌入势函数，建立了能够准确描述Ti2AlN/TiAl复合材料原子间相互作用的Ti-Al-N三元势能函数。基于此势函数模型，采用分子动力学方法从原子尺度揭示了复合材料摩擦磨损机制。研究发现，Ti2AlN颗粒的引入改善TiAl基复合材料的摩擦磨损性能，主要归因于Ti2AlN颗粒对复合材料的硬化作用和对位错运动的阻碍作用。复合材料中Ti2AlN/TiAl的界面类型、位错形态和位错密度，对材料摩擦磨损行为有较大影响。