原位生成TiB<sub>2</sub>颗粒增韧B<sub>4</sub>C陶瓷的研究

原位生成TiB₂颗粒增韧B₄C陶瓷的研究

摘要: 通过TiC与B₄C的化学反应,在B₄C基体内原位生成TiB₂颗粒,获得的TiB₂颗粒粒径一般在3μm以下。其中加入20vol%TiC(对应的TiB₂为35vol%)的复相陶瓷的断裂韧性值KIC达6.3MPa·m^1/2,比单体B₄C提高75%,加入10vol%TiC(对应的TiB₂为14vol%)的复相陶瓷的抗弯强度达到最大值620MPa,比单体B₄C提高40%。由B₄C和TiB₂颗粒之间热膨胀系数不匹配产生残余应力而引起的裂纹偏转和微裂纹增韧是主要的增韧机理,反应生成的碳对材料的强度和显微硬度有不良影响。

Abstract: Fine TiB₂ particles are produced in situ-B₄C through reaction of B₄C + 2TiC=2TiB₂+3C and B₄C-based composites are prepared by hot-press process at 2050℃. The composite derived from B₄C-20vol% TiC has a peak KIC value of 6.3MPa·m^1/2,which is higher than that of monolithic B₄C by 75%. The material resulting from B₄C-10vol%TiC enjoys a maximal bending strenght of 620MPa,which is 40% higher than that of monolithic B₄C. The crack denection and microcrack toughening caused by the residual stress resulting from the difference in thermal expansion coefficient between B₄C and TiB₂ are the main toughening mechanisms. The carbon derived from the reaction is one reason for the decrease in bending strength and Vickers hardness.