(TiB+TiC)/TC4 Composite Material Hot-press Reaction Sintering And Service Performance Research

Titanium matrix composites?TMCs?reinforced with ceramic particles have received considerable attention due to their high specific strength and specific stiffness,good corrosion and high temperature resistances.So,they have been widely applied in many fields,such as sporting goods,automotive,aerospace,advanced military and so on.However,the physical and mechanical properties of the composites are directly affected by the volume fraction and size of reinforcement,the distribution of reinforcement in the matrix,the interfacial bonding between the reinforcement and matrix.Therefore,optimizing the preparation process,such as sintering procedure,synthesis system and nominal volume fraction of the reinforcement,can contribute to obtain high performance composites.In these experiments,the 10 and 15 vol.%?TiB+TiC?/TC4composites were in situ synthesized from Ti-B₄C-C and Ti-TiB₂-TiC systems by reactive hot-pressed sintering at three temperatures?1200,1250 and 1300°C?.The effects of sintering temperature,synthesis system and nominal volume fraction of reinforcement on the phase composition,microstructures,mechanical properties?involving elastic modulus,Vickers hardness,bending strength and wear property?of the?TiB+TiC?/TC4 composites and the related influence rules and mechanisms of high temperature oxidation resistance were investigated.The experimental results or conclusions are as follows:The?TiB+TiC?/TC4 composites are mainly composed of TiB_w,TiC_p and Ti.The TiB_w and TiC_p are needle-like and near-equiaxed,respectively,and uniformly distributed in the TC4 matrix.With the same nominal volume fraction of reinforcement,the content of TiB+TiC reinforcement climbs with the sintering temperature increasing.Surprisedly,the number of pore increases markedly while synthesizing by the Ti-B₄C-C system at 1300oC,which can be attributed to the rapid nucleation and growth of TiB.All the density values of?TiB+TiC?/TC4 composites derived from the two systems are over96%.The elastic modulus and Vickers hardness values of the composites from the two systems increase in vary degrees with increasing the sintering temperature and the nominal volume fraction of reinforcement.In particular,all the elastic modulus and Vickers hardness values of the composites from the Ti-TiB₂-TiC system are higher than those from the Ti-B₄C-C system no matter what sintering temperature and nominal volume fraction of reinforcement,as a result that he maximum elastic modulus and Vickers hardness of 178.7 GPa and⁸00 HV can be obtained.Moreover,all the bending strength values of composites from the two systems increase firstly and then decrease with the sintering temperature increasing from 1200 to 1300oC.The bending strength values of composites from the Ti-TiB₂-TiC system are higher than those from the Ti-B₄C-C system while employing the same sintering temperatures and nominal volume fractions of reinforcement,and the maximum bending strength values of 1113 MPa can be obtained from Ti-TiB₂-TiC systems while sintering at 1250oC.By analyzing the friction coefficient,wear rate and SEM morphologies of wear surfaces of the?TiB+TiC?/TC4 composites,the?TiB+TiC?/TC4 composites from the Ti-B₄C-C system present better abrasion resistance than those from the Ti-TiB₂-TiC system no matter what sintering temperature and nominal volume fraction of reinforcement,which can be attributed to a certain graphite remained in the composites from the Ti-B₄C-C system.The?TiB+TiC?/TC4 composites were oxidized at 600oC,700oC and 800oC for 320 h,respectively.After that,the oxidation films on the?TiB+TiC?/TC4 composites are mainly composed of TiO₂,Al₂O₃ and V₂O₃.Moreover,the oxidation kinetics curves of the?TiB+TiC?/TC4 composites accord with the linear parabolic mixing rule,showing nearly parabola.According to the oxidation kinetics curves,the surface and sectional microstructures of oxide layer,the finer oxide film grains and thinner oxidation layer particles can be observed on the 15vol.%?TiB+TiC?/TC4 composites synthesized by the Ti-TiB₂-TiC system at 1250°C,resulting in less oxidation weight gain,indicating better oxidation resistance.