超重力下燃烧合成TiC-TiB_2细晶复合陶瓷

Microstructure,Properties and Toughening of TiC-TiB_2 Fine-grained Composite Ceramics Prepared by Combustion Synthesis under High Gravity

采用超重力下燃烧合成工艺,以快速凝固方式制备出TiB2系列含量的TiC-TiB2细晶复合陶瓷。XRD、FESEM与EDS分析表明,随TiB2含量的增加,TiC-TiB2复合陶瓷基体从TiC微米球晶组织逐渐转化为TiB2小尺寸片晶组织,且对于TiB2含量为50%的TiC-TiB2复合陶瓷,可获得TiB2小尺寸片晶均匀镶嵌于TiC基体上的共晶组织。力学性能测试结果表明,TiB2的摩尔分数为50%的TiC-TiB2复合陶瓷因在凝固过程中发生共晶反应,陶瓷相对密度和硬度均达到最高值(分别为98.6%和18.4GPa),并且因TiB2小尺寸片晶在裂纹扩展时所诱发的裂纹偏转、桥接及片晶拔出增韧机制的协同作用,TiB2的含量为66.7%的TiC-TiB2复合陶瓷具有最高的断裂韧度(13.4MPa·m0.5)。

With the help of combustion synthesis under high gravity,TiC-TiB2 fine-grained composite ceramics with different TiB2 contents were prepared by rapid solidification method.Microstructure and mechanical properties of the prepared composite ceramics were investigated by XRD(X-ray diffraction),FESEM(field emission scanning electron microscope) and EDS(energy dispersive spectrometer) as well as tensile testing.The results reveal that,with increasing in TiB2 content,microstructure of the TiC-TiB2 composite ceramics is composed of those from fine TiC spherical grains to fine TiB2 platelet structure,whereas when TiB2 content reaches 50%(in atom fraction),ceramics consist of eutectic structure where small-sized TiB2 platelets are embedded in TiC matrix.Relative density and Vickers hardness of TiC-50TiB2 reach up to maximum value(as 98.6% and 18.4GPa,respectively) as a result of eutectic reaction during solidification,meanwhile,TiC-66.7TiB2 ceramics exhibit maximum fracture toughness of 13.4MPa·m1/2 as a result of the cooperative action of crack deflection,crack-bridging and pull-out toughening from fine TiB2 platelets.