Study On Hot Forming,Microstructure And Properties Of 5vol.%TiC_p/near ? Ti Composite Component

Particle reinforced titanium matrix composites have better high strength and high temperature properties than alloys,and extensive prospect for aerospace applications.However,the as cast titanium matrix composites prepared by traditional melt casting method have some disadvantages,high strength but poor plasticity at room temperature.The microstructure and mechanical properties of the composites can be improved by hot working.Silicon is widely used to improve the high temperature properties of titanium alloys and titanium matrix composites,but the mechanism of silicide precipitation and its effect on the mechanical properties of the matrix have not been systematically studied.In this paper,the microstructure of 5vol.%TiC_p/Ti composite was optimized by forging with decreasing temperature,and the precipitation behavior and microstructure evolution of silicide at different phase transition temperatures were studied by hot deformation process.The deformation process parameters of forging preparation before forming titanium matrix composite component were established,and the final punching process parameters of the component were determined by finite element numerical simulation.The component was prepared and its microstructure and mechanical properties were analyzed.5vol.%TiC_p/Ti composites were forged by multi-directional forging with the decreasing temperature,which can significantly change the morphology of matrix and the size and distribution of reinforcement.After forging,the structure consists of elongated strips?phase and equiaxed?with grain size of about 20?m.The grain diameter of TiC_p is about 23?m.After hot compression deformation in the phase region(1080-1120?),the equiaxed structure transforms into elongated lamellae?There is no obvious change in TiC_p.In addition,the silicides of(Ti,Zr)₆Si₃ were found in the deformed microstructure,which decreased with the increase of deformation temperature and the decrease of strain rate.In hot compression deformation,the deformation.The dynamic recovery of?phase and partial dynamic recrystallization were mainly taken place,and the increase of strain rate can promote the occurrence of dynamic recrystallization.Silicide and lamellar structure are formed during the subsequent rapid cooling process.When the as-forged 5vol.%TiC_p/Ti composites were deformed in(?+?)region(845-965?),the matrix alloy were transformed into equiaxed structure,lamellar structure and residual structure?phase.The size and shape of TiC_p have no obvious change.In addition,the silicides of(Ti,Zr)₆Si₃ is still existed in the microstructure after hot deformation in the two-phase region.With the decrease of temperature and the increase of strain rate or strain,the number of silicide was increased.TEM observation shows that a large number of dislocations exist at TiC_p and?/?interfaces during hot deformation,and the density of silicide is higher near the recrystallized?phase region after deformation,which hinders the movement of dislocations and the migration of recrystallized grain boundaries.In the two-phase region,dynamic recovery and partial dynamic recrystallization were mainly occurred.The trend of dynamic recrystallization increases with the increase of deformation temperature and the decrease of strain rate.The punching process of TiC_p/Ti composite ring was simulated by DEFORM-3D software.The damage value,maximum principal stress,equivalent strain,equivalent stress and deformation load were analyzed by changing the deformation process parameters.The increase of deformation rate and the decrease of deformation temperature will lead to the damage value and maximum principal stress of TiC_p/Ti composite in the punching process,the load increases and the deformation load decreases gradually.The microstructure of TiC_p/Ti composite ring is composed of strip?phase,equiaxed?phase,a small amount of residual?transformation structure,silicide and sheet TiC_p.The results show that the silicide and TiC_p are uniformly distributed at the grain boundary,which promotes the refinement of the matrix and the recrystallization process in the deformation process.The recrystallization process in the component punching process follows the continuous recrystallization mechanism.The results show that the room temperature tensile strength of TiC_p/Ti composite component is obviously improved,mainly due to fine grain strengthening and dislocation strengthening.The high temperature tensile strength and plasticity of TiC_p/Ti composite component decrease and increase with the increase of temperature,respectively.The main reason is that the increase of temperature accelerates the diffusion ability of atoms,the hindrance of TiC_p and silicide to matrix and dislocation is greatly weakened,and the movement of dislocation and grain boundary is active.