| As one of the military strategic materials,boron carbide has the characteristics of low density and high hardness,and its excellent chemical inertia and high temperature stability make it expected to play an important role in the future structural applications.However,the low diffusion coefficient of boron carbide ceramics caused by strong covalent bonds makes it difficult to sintering and compact,and the mechanical properties of materials often decrease due to the growth of grains in the sintering process.The traditional sintering method did not greatly improve the mechanical properties of boron carbide.If the oscillatory forging technology is adopted,the plastic deformation and crystal boundary sliding process of the material under the oscillation force field can be greatly improved,which is expected to improve the material compensification and mechanical properties.This project combines oscillatory sintering technology with forging process,and adopts thermal oscillation forging method to conduct oscillatory high temperature forging of B4C ceramic materials,aiming to regulate the plastic deformation process and degree through oscillation load,and achieve a significant improvement in mechanical properties.Through the study of thermal pressure forging and oscillation forging of dense B4C ceramics under different conditions,to explore the influence of oscillating force field on the forging deformation process;Through the study of oscillatory forging sintering of porous B4C ceramic billet,to explore the influence of oscillatory forging sintering on the compaction and performance of B4C ceramics.Through the comparison of three methods of thermal forging,oscillation forging and oscillatory forging sintering,to explore the main mechanism of mechanical performance improvement of boron carbide ceramics.The following conclusions are obtained from the experiment:（1）As the thermal pressure forging and oscillation forging increase with the forging temperature,greater plastic deformation and strain rate are realized.The grain orientation tends to show the preferred orientation perpendicular to the top surface,resulting in stronger hardness and bending strength of the sample;（2）Under the same conditions,the oscillation forging sample performance is better than the thermal pressure forging,because the introduction of the oscillation pressure increases the plastic deformation and crystal boundary slip degree;（3）When forging the boron carbide sample through oscillation,the best forging effect can be achieved when the oscillation frequency is 5 Hz;（4）The sample prepared after oscillation forging sintering of porous boron carbide is stronger than the thermal pressure forging and oscillation forging in the mechanical properties of the material.The bending strength of the samples obtained after oscillatory forging sintering at 1900℃reached 955 MPa.Because there are pores in the porous body,it is more conducive to the diffusion and sliding of the crystal boundary,coupled with the introduction of oscillation pressure,which can promote the friction and rotation between the crystal boundary,making it in the optimal fit state and improving the mechanical properties of the material.Compared with the traditional preparation process,its bending strength is nearly doubled. |
