Study On Microstructure,Mechanical Properties And Hot Deformation Behavior Of In Situ Synthesized?TiC+Ti₅Si₃?/Ti Composites

Titanium matrix composites?TMCs?,combined with high specific strength,low density good specific modulus and resistance to oxidation,have considerable potential for improving properties and can be applied in aerospace systems.However,poor room-temperature ductility and hightemperature deformation resistance of TMCs limit their engineering and business application.In this paper,TMCs reinforced with different volume fractions of?TiC+Ti₅Si₃?were prepared by vacuum induction melting technology.The influence of reinforcement content,hot compressive deformation and heat treatment on microstructures and mechanical properties was investigated.The corresponding relationship between microstructure and properties was analyzed.In situ synthesized TiC and Ti₅Si₃ were products as reaction between Ti and SiCp.TiC and Ti₅Si₃ were prone to be segregated in primary ? grain which restrict the growth of ? grains by pinning the grain boundary.The grain size of composites decreased from 639?m to 61?m with the reinforcement content range from 0 to 15 vol.%.The strengths and hardness of composites with 0-5vol.% reinforcement were improvedwith the increased of reinforcements contend,the ductility changed in opposite way.The hot compression behavior of 2vol.%?TiC+Ti₅Si₃?/Ti was studied by the thermal physical simulation method.The flow stress and peak stress decreased with increasing deformation temperature and decreasing strain rate.The calculation of the composite deformation activation energy was 507.02KJ/mol and the constitutive equation was established.The processing map showed that the proper strain rate was in 0.001-0.01s-1 range when the composites were deformed near the ? transition temperature.The degree of ? phase globularization was increased with increasing of deformation temperature and decreasing strain rate.The main softening mechanism of the two-phase region was dynamic recrystallization,? phase bending and globularization.The main softening mechanism of the single-phase region was dynamic recovery.Based on the hot working map,2vol.%?TiC+Ti₅Si₃?/Ti composites ingot was deformed in a way of upsetting and from several directions.The as-forged composites were solid solution and aging treatment at different temperatures.Reinforcements were stable in the process of heat treatment,which can restrict the growth of grains under high temperature.The mechanical properties of composite by solution treatmentin two-phase region were better than those in single-phase region.The precipitation of secondary ? phase was the main reason for the increase in strengths of the composites after heat treatment.With temperature decreasing,secondary ? phase size decreased,which made the strength of composites improve.At 760 ? /50min/AC+520 ? /8h/AC,the comprehensive mechanical properties of composites was the best.The tensile strength was up to 1333 MPa,and the elongation rate was 6.6%.