A Study On Preparation,Microstructure And Mechanical Properties Of B₄C/SiC And B₄C/TiB₂ Ceramic Composites

Boron carbide ceramics have a wide range of applications such as military bulletproof,aerospace,wear-resistant and corrosion-resistant parts,etc.,with low density,high melting point,high hardness,high temperature resistance,corrosion resistance and good neutron absorption performance and other characteristics.But the difficulties of the sintering process and the related mechanical properties at room temperature have limited the further application of boron carbide ceramics.In this paper,boron carbide-based ceramic composites were prepared by two processes:atmospheric sintering and hot-pressing sintering.The thesis studied the preparation,microstructure,and mechanical properties of B4C/SiC and B4C/TiB2 ceramic composites in details.Material toughening and strengthening design,and the production and application of boron carbide composites have a certain theoretical guidance significance and application value.In this paper,B4C/SiC ceramic composites were first prepared by atmospheric sintering process.The sintering aids YAG,Ti and C and the sintering temperature on the structure and properties of the materials were studied.The results showed that a small amount of YAG was beneficial for the densification of B4C/SiC composites.When 5%YAG was added,the maximum relative density of the material was 95%,and the increase in YAG content or sintering temperature was not conducive to the densification of the material.Volatile oxides were generated for the reaction of YAG with B4C,leaving many pores on the substrate after sintering,which reduced the density and mechanical properties of the material;the addition of 3%Ti was beneficial for the densification of B4C/SiC composites,but When the sintering temperature was too high or Ti was added in a large amount,the molten Ti reacted in the matrix at a high temperature to form a special shell structure,and holes were formed in the matrix,so that the maximum flexural strength of the material was only 204 MPa;adding 3.5%C It can reduce the oxide layer on the surface of boron carbide and silicon carbide,reduce its surface energy,and promote sintering densification.The flexural strength and fracture toughness of the composite material reached 294 MPa and 4.5 MPa·m1/2 when sintered at 2050℃,respectively.Secondly,B4C/TiB2 ceramic composites were prepared by using B4C,TiO2 and TiC powders as the main raw materials under the hot-pressing sintering process of 1500℃ × 60 min(vacuum)+1900℃ × 60 min(vacuum).Effect of microstructure and properties of B4C/TiB2 ceramic composites.The results showed that TiO2 or TiC in the raw material can undergo in-situ chemical reaction with the boron carbide matrix to form TiB2 particles.The in-situ generated TiB2 particles have the effect of strengthening and toughening the B4C ceramic composites.Among them,the additive TiC was more effective than TiO2.This was because TiO2 introduces O,which was not good for sintering and densification.When the TiC content was 10%,the flexural strength and fracture toughness of B4C/TiB2 ceramic composites reached 589 MPa and 5.24 MPa·m1/2,respectively.