SiC晶须对反应合成多孔TiB_2-TiC复合材料的影响

以Ti、B_4C和SiC晶须(SiC_w)为原料,采用自蔓延高温合成法制备了多孔TiB__2-TiC复合材料。讨论了SiC_w含量对TiB__2-TiC复合材料物相、组织形貌、孔隙率和抗压强度的影响。结果表明:不添加SiC_w时,复合材料中主要物相为贫硼相TiB和Ti_3B_4以及TiC和少量TiB__2;在5Ti+B_4C体系中加入SiC_w后,贫硼相TiB和Ti_3B_4逐渐减少直至消失,而出现富硼相TiB__2和TiC的含量增加。随着SiC_w含量的增加,复合材料的孔隙率逐渐增加,由38.46%增加至5_2.78%。当SiC_w含量小于1.0时,随着SiC_w含量的增加,多孔TiB_2-TiC复合材料的抗压强度明显增加,当SiC_w含量为1.0时,复合材料的抗压强度达到最大值56.04MPa。Ti与SiC_w反应会生成TiC、Ti_3SiC_2和TiSi_2等物相,消耗一定量的Ti,使得与B4C反应的Ti量减少,从而促进富硼相TiB_2形成和TiC的增多。并且在SiC_w表面形成颗粒状TiC或者层片状Ti_3SiC_2,增加SiC_w与TiB_2-TiC基体之间的结合,更有利于发挥SiC_w的强化作用。

Effects of SiC whiskers on TiB2-TiC porous composites by reaction synthesis

Porous TiB₂-TiC composites were produced by self-propagating high-temperature synthesis method, with Ti, B₄C and SiC whiskers(SiC_w) as raw materials. The effects of SiC_w content on phases, microstructures, porosity and compressive strength of TiB₂-TiC composites were studied. The results show that the composites are mainly composed of poor boron phases TiB and Ti₃B₄, TiC and a little TiB₂ when there is no SiC_w added. After adding SiC_w into 5Ti+B₄C system, the poor boron phases TiB and Ti₃B₄ decrease and even disappear, while the content of rich boron phase TiB₂ and TiC increase. With the increasing of SiC_w content, the porosity of composites gradually increases from 38.46% to 52.78%. When the content of SiC_w is less than 1.0, the compressive strength of porous TiB₂-TiC composites improves significantly with the increasing of SiC_w content and reaches to the maximum value of 56.04 MPa when the content of SiC_w is 1.0. A part of Ti is consumed by reacting with SiC_w to form TiC, Ti₃SiC₂ and TiSi₂ phases, so less Ti is remaining to react with B₄C. This promotes the formation of rich boron phase TiB₂ and TiC. Moreover some of the granular TiC or lamellar Ti₃SiC₂ grow around the surface of SiC_w, which is beneficial to improve the bonding strength of SiC_w and TiB₂-TiC matrix, and the effect of SiC_w reinforcement.