碳含量对无压烧结碳化硅陶瓷的显微组织和力学性能的影响

Effect of Carbon Content on Microstructure and Properties of Pressureless-sintered Silicon Carbide

在碳化硼添加量为1wt%的条件下,考察不同碳含量对2000℃下制备的无压固相烧结碳化硅陶瓷的显微组织和力学性能的影响。实验结果表明:物相分析显示不同C含量的SiC陶瓷样品的XRD衍射图谱近似相同,其中主相均为SiC,检测到少量C,未检测到B_(4)C相。当C含量为3wt%时,SiC陶瓷样品的力学性能达到最佳,其相对密度、抗折强度、断裂韧性与维氏硬度分别为98.6%、452 MPa、4.5 MPa·m^(1/2)和30 GPa。继续增加碳含量,SiC晶粒存在局部异常长大现象,相应样品的力学性能也有所下降。

In the present study,using samples with 1wt%B_(4)C addition prepared by pressureless sintering at 2000℃,the effect of carbon content on the microstructure and mechanical properties of solid-state sintered silicon carbide ceramics was investigated.The experimental results were as follows:XRD patterns of all samples with different carbon content were almost same with each other.SiC as main phase and a trace amount of C were identified,B 4C phase was not detected.When carbon content was 3wt%,the sample showed the optimum mechanical properties of which the volume density,relative density,bending strength,fracture toughness and Vickers hardness were 98.6%,452 MPa,4.5 MPa·m^(1/2),30 GPa,respectively.With increasing carbon content,the grain size of silicon carbide gradually increased and some abnormal grain growth occurred which could decrease the mechanical properties of this material.