Hot Compression Behavior And Forging Process Of TiB_w Reinforced Near ? High Temperature Titanium Matrix Composite

The in situ titanium matrix composites have good high specific strength,specific modulus and excellent heat resistance,It has broad application prospects in aerospace,automobile industry and other fields.Therefore,it is necessary to study the microstructure and mechanical properties of in-situ titanium matrix composites.This paper takes advantage of the reaction in-situ of Ti and TiB₂under the high temperature,prepard 3%TiB_wreinforcing Ti-6Al-4Sn-10Zr-1Mo-1Nb-1W-0.3Si matrix composites through the vacuum induction melting method,studies the hot compression deformation of composite matarils,reveals the influence rule of hot deformation process to the microscopic structure,the thermal deformation process parameters were optimized,as well as illustrates the influences of different forging process to the microscopic structure and mechanical property of composite materials.It applies the hot compression simulation experiment to analyze TiB_w/near?titanium matrix composites,the sensitivity of materials to deformation temperature and strain rate is high,and the stress will be gradually reduced along with the temperature rise of hot deformation and reduction of strain rate.The thermal activation energies for TiB_w/near?titanium matrix composites in the two-phase region and single-phase regionr respectively are:758.55KJ/mol,220.51KJ/mol.It constructs the constitutive equations for TiB_w/near?titanium matrix composites in different phase regions;draws the hot machining map under 0.8true strain,and carries out the advantages and disadvantages analysis for hot deformation machining of different deformation parameter according to the hot machining map,as well as concludes that the most appropriate hot deformation region for the composite materials is:880??950?,0.01s^-1?0.1s^-1.It systematically researches the microstructure evolution of TiB_w/near?titanium matrix composites under the different hot compression deformation parameters.In the two phase region,As the deformation temperature increases,and the nodulizing process is expedited along with the rise of deformation temperature,and the more the temperature close to the phase transformation point,the lower the content of spheroidization?;Along with the increase of strain rate,the lamellar structure is easy to be extended and deformed,and the more uneven the matrix structure is.In the single-phase region,the high temperature causes the?grains to grow.The softening mechanism of TiB_w/near?-titanium matrix composites was explored.The softening mechanism in the two-phase region is mainly the dynamic recrystallization,the specific manifestation is the spheroidization of the layer?,and the mechanism is the grain boundary separation.The softening mechanism of the single-phase region is mainly based on?incomplete dynamic recrystallization and dynamic recovery.Baed on the above analysis,it applies TiBw/near?titanium matrix composites button ingot casting to perform the one-way forging and one pass multi-direction forging under the different deformaiton process parameters.In the one-way forging,the smaller the strain rate is and the larger the deformation will be,the content of isometric?-phase will be higher and the recrystallization will be more sufficient.After the multi-direction forging,the crystalline grain will be refined,the reinforcing phase is evenly distributed.Using a large ingot to carry out different multi-directional forging,which successfully produced the TiBw/near?titanium matrix composites with small grain size and even size distribution,as well as the grain size and size distribution will be gradually reduced alogn with the increase of deformation passes.Under the room temperature,the strength of extension and percentage of elongation are increased along with the increase of deformation passes.The room temperature strength of extension after four passes multi-direction forging is 1373MPa and the percentage of elongation reaches 2.13%,which has a significant improvement compared with the cogging-down forging.If the temperature is 650?,along with the increase of deformation passes,the increase amplitude for strength of extension of materials is larger than the reduction amplitude for percentage of elongation,and the high temperature comprehensive performance will be enhanced,the strength of extension after four-phase multi-direction forging is strength of extension and the percentage of elongation reaches 28%of the maximum value.The research to forging process of TiBw/near?titanium matrix composites provides the effective reference for the hot machining deformation of various titanium matrix composites.