【作者】 代威；

【导师】 傅正义；

【作者基本信息】 武汉理工大学 ， 材料学， 2004， 硕士

【摘要】 自蔓延高温合成快速加压技术（SHS／QP）是一种节能高效的新型材料制备技术，它充分利用了SHS过程的优点，将其与动态快速加压过程有机地结合起来，一次完成材料的合成与密实化过程。其特点是成本低，制备时间短，各种工艺参数可自由调节，整个过程自动控制，设备简单，产品尺寸可较大并具有特殊的性能。 SHS／QP技术制备陶瓷及陶瓷基复合材料耗时短（＜5min），产物密度接近理论密度，用传统的扩散烧结机理很难解释，预示着不同的烧结机理。本文用SHS／QP工艺制备TiB₂陶瓷材料和TiB₂—Al₂O₃复相陶瓷，通过分析不同工艺条件对产物微观结构及残余应力的影响，提出了新的陶瓷材料SHS／QP超快速烧结机理。 单相陶瓷材料SHS／QP超快速烧结机理：SHS反应后热量来不及散失，试样处于半固态。经过一定延迟时间对其施加一定的准等静压，陶瓷晶粒在高温高压下发生塑性变形及流动，杂质气体被排出，晶粒间通过扩散作用形成烧结颈部，最终得到密实化的烧结产物。材料烧结致密化主要由晶粒的粒子重排和塑性重排机制所控制；晶粒在高温下的扩散蠕变对晶粒间烧结颈部的连接有贡献，但受烧结时间的限制，对材料的烧结致密化贡献十分有限。 复相陶瓷体系SHS／QP超快速烧结机理：SHS反应完成后，产物处于高温下的液一固混合态，材料烧结致密化主要由液相存在条件下晶粒的粒子重排和塑性重排机制所控制，主要通过各晶粒沿着有液相存在的晶界的相对滑动、转动和自身塑性变形方式来进行：液相的存在加快了颗粒重排和塑性重排的进程，同时液相填充孔隙和晶粒问的空隙，进一步提高了材料的致密化程度；固相的晶粒间扩散受到液相的限制，使得固相晶粒尺寸较小，扩散作用受烧结时间的限制，对材料的烧结致密化贡献十分有限。更多还原

【Abstract】 Self-propagating High-temperature Synthesis/Quick Pressing or SHS/QP is a new processing technique with high efficiency and low cost. In the process, following the SHS reaction, when the sample is still in a red hot and soft state, a quick and high hydraulic force is applied on the sample, so that dense product can be obtained.The relative density of ceramic composites fabricate by SHS/QP in few minutes was nearly theoretical, which is hard to explain by traditional diffuse sintering theory and indicates a new sintering mechanism. In this paper, the TiB2 ceramic and TiB2-AI2O3 composites were processed by SHS/QP, and the microstructure and residual stress of the products under different relevant parameters were studied. A new mechanism of superfast sintering of ceramic composites by SHS/QP was firstly represented.The mechanism of sinter single-phase ceramic by SHS/QP is: after SHS the product is in a state of semi-solid because of the extra high combustion temperature. Once the reaction completes, and at a pre-established time delay, a quick and high hydraulic force is applied on the sample. The re-arrangement and plastic deformation of the grains under high temperature and pressure lead to the densification of the product. The gas impurities are excluded and finally the dense ceramic is obtained. The diffuse of the grains strengthens the neck of sintering. However, it has few contributions to the densification of materials due to the time limit.The mechanism of sinter diphase ceramic by SHS/QP is: after SHS the product is liquid-solid mixture because of the extra high combustion temperature. Once the reaction completes, and at a pre-established time delay, a quick and high hydraulic force is applied on the sample, which cause the re-arrangement by the gliding, turning of the grains following the channel of liquid and then the plastic deformation. At the same time thegrowth and diffuse of the solid grains are proceeding but limited by the extinction of liquid phase. The extinction of liquid phase accelerates the re-arrangement of the grains and enhances the densification by filling the clearance between solid grains. Since the time when the product is in high temperature is very short, the contribution of the diffuse is very limited to the densification of diphase composites, which is controlled by the re-arrangement and plastic deformation of the grains under high temperature and pressure.更多还原