石墨烯增强钛基复合材料组织性能调控及强韧化机制研究

Taking advantage of the high Young's modulus, breaking strength, ultrahigh heat conductivity coefficient and electronic mobility of grapheme and the microwave rapid heating, a new type of high tenacity, high heat conductivity and high temperature resistance of graphene reinforced titanium matrix composites will be prepared by high vacuum microwave sintering, in which the copper plating grapheme is uniformly distributed over the titanium alloys matrix through the electrostatic self-assembly combined of ultrasonic-assisted stirring method. The interfacial reaction, interface bonding behavior and stress characteristics between the reinforcements and the matrix will be analyzed through the investigation of interfacial morphologies, microstructure and phase, which also comprehends the improvement of the interfacial compatibility mechanism using the graphene copper plating and evenly dispersed method. Electronic state of titanium atoms in the interface between titanium and grapheme will be calculated by Density Functional Theory, in which the diffusion mechanism will be explored, the grain growth kinetic index and the growth activate parameters will be confirmed and the grain growth model also will be established. The stress field and strain field of the grapheme reinforced titanium matrix composites will be studied by finite element modeling. At the same time, combination of the dislocation movement and stress transfer process for grapheme, the densifying and strengthening and toughening mechanism of grapheme reinforcement combined of microwave sintering for the titanium matrix composites can be revealed. In this project, the interface compatibility theory of the grapheme and titanium matrix will be perfected, and the strengthening and toughening mechanism of the grapheme reinforced titanium matrix composites with microwave sintering will be enriched.

利用石墨烯高的杨氏模量、断裂强度，超高导热系数和电子迁移率以及微波快速加热等优点，通过一种静电自组装结合超声辅助搅拌的方法将镀铜石墨烯在钛合金基体中均匀分散，经高真空微波烧结制备出一种新型高强韧性、高热导和耐高温的石墨烯增强钛基复合材料。通过石墨烯与基体界面形貌、组织与结构等特征分析增强相与基体界面反应、界面结合行为与应力特征，理解石墨烯镀铜和均匀分散对改善石墨烯与钛基体的的界面相容性机制。通过密度泛函理论计算研究来钛原子和石墨烯界面中钛原子的电子状态，探索其扩散机制，确定晶粒生长动力学指数和生长激活能参数，建立晶粒生长模型，并采用有限元模拟来研究石墨烯/钛基复合材料的应力场和应变场，同时结合石墨烯对位错运动以及应力的转移过程，理清石墨烯增强和微波烧结协同致密化、强韧化钛基复合材料的机理。本项目完善了石墨烯与钛基体界面相容性理论基础，丰富了微波烧结协同石墨烯增强钛基复合材料的强韧化机制。

将高杨氏模量，高断裂强度，超高导热系数和电子迁移率及高温性能良好的石墨烯引入钛合金基体中，不仅可以改善钛合金硬度低、耐磨性差、使用温度较低的特性，而且能进一步提高钛合金比强度、比模量和高温蠕变性能、疲劳性能、耐磨性和抗氧化性等。本项目先通过对石墨烯进行表面镀铜来增加石墨烯与基体的相容性和润湿性，其次采用一种静电自组装结合超声辅助搅拌的方法将石墨烯在 TC4 基体中均匀分散，复合粉体压制后通过微波、热压和等离子烧结来提高其致密度，并结合石墨烯镀铜来抑制石墨烯与 Ti 的反应，控制 TiC 相含量，以充分发挥石墨烯的强化作用。三种烧结的镀铜石墨烯钛基复合材料的抗压强度均比基体有较大提高，热压烧结和等离子烧结制备的铜石墨烯钛基复合材料抗压强度比微波烧结均有较大提高，其中热压烧结提高效果最为显著。使用第一原理对Ti/g石墨烯, Ti/CVG, 和 Ti/石墨的分离功和界面能系统研究表明，Ti/CVG接口具有比Ti/石墨烯和 Ti/石墨分离功更大，界面能更低，表明钛和有缺陷的石墨烯之间界面反应比原始的Ti/石墨烯界面更强。研究结果也揭示了Ti/石墨烯分离功与界面能的关系非常接近于Ti/石墨对应的值，表明石墨层的范德华力比界面的Ti-C化学键弱得多。（GNPs-Cu）/Ti6Al4V复合材料强化机制是的GNPs，Ti2Cu和少量TiC强化。Cu与基体之间良好的润湿性保证了GNPs与基体能产生良好的界面结合，且降低GNPs与基体中Ti的反应程度，使得GNPs得以很好保留，因此石墨烯的强化是主要强化机制。烧结过程中流动的 Cu与基体生成的Ti2Cu相弥散分布在基体中阻碍位错的运动，产生第二相强化。烧结过程中反应生成的少量TiC颗粒限制了基体晶粒的长大，防止了位错运动。石墨烯增强钛基复合材料等温压缩实验表明建立的本构模型能很好地预测复合材料的流变行为；加工图上有少量不稳定区，表明该材料具有良好的热加工性。复合材料在变形过程中动态回复起主要作用，同时伴随着少量的动态再结晶。随着氧化温度的增加，GNPs-Cu/Ti6Al4V复合材料的氧化规律由抛物线型转变为直线型，石墨烯含量增加，GNPs-Cu/Ti6Al4V复合材料的抗氧化性能也越好。本研究为石墨烯钛基复合材料在航空航天、化学和汽车工业等领域应用奠定良好基础。