Study On Sintering And Mechanical Properties Of TiB₂-based Composite Ceramics

With the rapid development of military science and technology,various weapons with strong lethality emerge in an endless stream,and the threats to combat personnel,weapons and equipment are becoming more and more serious.The development of high-hardness,high-strength,high-toughness,and low-density protective materials is not only an indispensable survival foundation in modern warfare,but also an important military guarantee for the country’s long-term stability.TiB₂ ceramics have many excellent properties such as high hardness,high wear resistance and high compressive strength,which are widely used in harsh environments such as high temperature,high pressure,and easy corrosion.Its ceramic matrix composite material has become one of the important development directions in the field of armor protection materials in recent years.As the research of TiB₂-based ceramics,researchers are mostly focuse on the static mechanical properties.While,there are relatively few studies on the dynamic mechanical properties of TiB₂-based ceramics,especially the crushing behavior under impact loading.As a TiB₂-based ceramic for special purposes such as armor protection,improving its strength and toughness through experiments,and studying its dynamic mechanical properties can provide basic data for the field of armor protection,which has important military value and guiding significance for improving armor protection.In this paper,TiB₂-B₄C and TiB₂-B₄C-Si C_W ceramics were prepared by hot pressing and SPS through using TiB₂ powder as matrix,adding B₄C powder and Si C_Was reinforcing phase.The effects of B₄C and Si C_W content on the microstructure and mechanical properties of TiB₂-based ceramics were investigated.Combined with the relevant application background of TiB₂-based ceramics,the dynamic mechanical properties based on anti-penetration performance and SHPB test were investigated.The relevant conclusions are as follows:（1）The TiB₂-B₄C ceramics prepared by hot pressing sintering can effectively refine the grains,promote the densification of the microstructure and improve the mechanical properties due to the addition of B₄C.When the addition amount of B₄C reaches 20 wt.%,TiB₂-B₄C ceramics have relatively prior comprehensive properties,the Vickers hardness,fracture toughness and bending strength are 27.63±1.73 GPa,4.77±0.06 MPa·m^1/2,612.5±28.78 MPa,respectively.Si C_W can further refine the microstructure,improve the mechanical properties of TiB₂-B₄C-Si C_W ceramic composites,and improve the stability of composite performance.When the addition amount of Si C whiskers is 6 wt.%,the relative density,Vickers hardness,bending strength and fracture toughness of TiB₂-B₄C-Si C_Wceramic composites are 99.96%,19.79±0.73 GPa,724±60.54 MPa,6.7±0.34 MPa·m^1/2,respectively.（2）SPS can quickly prepare TiB₂-B₄C and TiB₂-B₄C-Si C_W ceramics.As the second phase,B₄C can significantly improve the sintering performance,promote densification effectively,and inhibit the abnormal growth of grains at the same time.When the addition amount of B₄C is 10 wt.%,TiB₂-B₄C ceramics have relatively good comprehensive properties,the Vickers hardness,fracture toughness and bending strength are 24.65±0.66GPa,3.16 MPa·m^1/2,730.65±74.11 MPa,respectively.Its Vickers hardness and fracture toughness values are lower,but the flexural strength values are higher than the composites sintered by HP.Si C_W can react with oxides on the surface of TiB₂ powder to improve sintering performance and increase the density of ceramics,and a very small amount of Ti C will be generated in this process.At the same time,during the cooling process,the micro-cracks generated because the thermal expansion coefficients of various substances are not match.Microcracks propagate forward through crack deflection and crack branching,etc.In this process,the crack propagation path will be extended and more energy will be consumed,thereby improving the fracture toughness of TiB₂-B₄C-Si C_W ceramic composites.The addition of Si C_Walso further improves the mechanical stability of the ceramics.When the addition amount of Si C whiskers reaches 6 wt.%,the overall performance of TiB₂-B₄C-Si C_W ceramic composites is the best,and its relative density,Vickers hardness,bending strength and fracture toughness are 99.7%,20.32±0.87 GPa,618.42±61.03 MPa,7.11±0.4 MPa·m^1/2,respectively.（3）In the anti-penetration performance experiment,the analysis shows that the penetration resistance of TiB₂-20wt.%B₄C ceramics and single-phase TiB₂ceramics is better than that of single-phase B₄C ceramics.（4）In the SHPB test,the waveforms of different shapes will correspond to different degrees of failure of the specimen,and the"broken"and"crushed"of the specimen correspond to the"single peak"and"double peak"of the waveform diagram of the specimen respectively;The failure degree of specimens increases with the increase of rod impact velocity.