B_(4)C-SiC复合陶瓷的制备及其物理力学性能研究

Study on the Preparation of B_(4)C-SiC Composite Ceramics and Their Physical-Mechanical Properties

为提升B_(4)C基陶瓷的力学性能,利用热压烧结工艺在不同压力(30,35,40 MPa)下制备了B_(4)C-20%SiC(质量分数)复合陶瓷试样,并对其物理力学性能进行了研究。利用阿基米德排水法、压痕法、三点弯曲法、单边切口梁法测定复合陶瓷的密度、气孔率、维氏硬度、弯曲强度以及断裂韧性,同时利用扫描电子显微镜和X射线衍射仪分析并表征复合陶瓷的微观组织、物相组成、断口形貌等。研究结果表明,B_(4)C-SiC复合陶瓷主要由B_(4)C和SiC两相组成,其微观组织随着烧结压力的增大而变得更加致密;当烧结压力由30增至40 MPa时,B_(4)C-SiC复合陶瓷的密度由2.22增至2.64 g·cm^(-3),气孔率由1.47%降至1.02%,维氏硬度由17.0升至32.6 GPa,弯曲强度由312.7提升至447.6 MPa,断裂韧性由4.79增至7.21 MPa·m^(1/2)。当烧结压力达到40 MPa时,复合陶瓷断裂过程中,发生裂纹偏转,这种现象与致密的微观组织以及B_(4)C和SiC热膨胀系数不匹配有关。

To improve the mechanical properties of B_(4)C based ceramics,B_(4)C-20wt%SiC composite ceramics were prepared by hot-pressing sintering under different pressures(30,35 and 40 MPa),and the physical-mechanical properties of composite ceramics were studied.The Archimedes method,indentation method,three-point bending method and single edge notched beam(SENB)method were used to test the density,porosity,Vickers hardness,bending strength and fracture toughness of the composites.SEM and XRD methods were used to analyze the microstructure,phase composition and fractured morphologies of the B_(4)C-SiC composite ceramics.The results showed that the B_(4)C-SiC composite ceramics were mainly composed of B_(4)C phases and SiC phases,and their microstructure became denser with the increase of sintering pressure.When the sintering pressure increased from 30 to 40 MPa,the density of B_(4)C-SiC composite ceramics increased from 2.22 to 2.64 g·cm^(-3),the porosity decreased from 1.47%to 1.02%,the Vickers hardness increased from 17.0 to 32.6 GPa,the bending strength increased from 312.7 to 447.6 MPa,and the fracture toughness increased from 4.79 to 7.21 MPa·m^(1/2).When the sintering pressure was 40 MPa,the crack deflection phenomenon was significantly observed on the fracture morphology of the composite,and the reason for this phenomenon may be related to the dense microstructure and the thermal expansion coefficient mismatch between B_(4)C and SiC phases.