原位钛基复合材料中TiB的生成热力学及动力学

采用自蔓延高温合成（SHS）、感应熔炼和熔模精铸相结合的方法，利用Ti—B—Al体系制备出了原位自生TiB增强的钛基复合材料。借助XRD、SEM和TEM分析了复合材料的物相和增强体的形态。结果表明：在复合材料中只存在TiB增强体和Ti，无TiAl3杂质相形成，TiB增强体呈柱状短纤维，这与其B27晶体结构有关，且增强体／基体界面清洁无杂质污染，并从热力学和动力学两方面论述了在Ti—B—Al体系中制备TiB增强体的生成机制：在Ti-B—Al体系中，Al首先受热熔化使得Ti和B相继溶解于Al液中；Ti与Al之间先行发生化学反应形成Ti—Al金属间化合物，放出的热量进一步引发了溶解于液相中的B和Ti产生高温自蔓延形成Ti—B化合物。以热力学理论分析，应最终形成TiB2，但实际上由于动力学影响，最终形成了TiB。

Thermodynamics and Dynamics of TiB Formation in In-Situ Titnaium Matrix Composite

By use of combined self-propagating high-temperature synthesis, induction melting with investment casting, in-situ TiB reinforced titanium matrix composite is fabricated in Ti-B-Al system. Phase identification and reinforcement morphologies are performed with XRD,SEM and TEM. The results show that there only exist TiB reinforcement and Ti phase, and there is no impurity of TiAl_3 phase in the composite. TiB is prism-like short-fibre, which relates to B_27 crystal lattice. The reinforcement/matrix interface is clean. The formation of TiB reinforcement in titanium matrix composite fabricated in Ti-B-Al system is discussed in aspects of both thermodynamics and dynamics: after Al melts in Ti-B-Al system, Ti and B dissolve into liquid Al one after another. Ti and Al react firstly and form Ti-Al intermetallic compound. The quantities of heat are so high that the SHS reaction form Ti-B compound between Ti and B dissolved in liquid Al. TiB_2 should be formed according to thermcynamics analysis, but final resultant of chemical reaction is TiB due to dynamics factor.