Research On The Microstructure And Properties Of Particle-Reinforced High-Temperature-Resistant Titanium Matrix Composites Prepared By Spark Plasma Sintering Process

High temperature resistant titanium alloys and composites have significant application in aerospace engines and other fields.In this dissertation,spark plasma sintering（SPS）was used to prepare matrix alloy Ti750,5vol.%SiCp+1vol.%B₄C+Ti750 composite,5vol.%SiC_p+5vol.%SiC_w+Ti750 composite,5vol.%SiCp+0.15vol.%GPLs+Ti750 composite and 5vol.%SiCp+Ti750 composite by ex-situ reinforcement of SiCp,SiCw,B₄C,and GPLs with the matrix alloy Ti750（new high temperature resistant titanium alloy）,and by in-situ reinforcement of TiC by the reactions of SiC+Ti→TiC+Si between SiCp and the matrix alloy Ti750.The effects of the mixed power,the reinforcements（ex-situ and in-situ）,solid-solution process,solid solution and aging process,and preparation process on the microstructure and properties of the materials were studied.The results are as follows:（1）Upon addition of reinforcements,the powders are significantly refined and contain acicular and granular particles.Among the five powder formulations,reinforcements with 5vol.% SiCp shows better refining effect with few agglomeration of particles.（2）The microstructures and phases composition of the ex-situ prepared composites contain SiC and B₄C particles homogeneously distributed in theα-Ti matrix.The in-situ synthesized composite block however,mainly contains TiC,SiC,and Ti₅Si₃ reinforced phases in the Tirich matrix.The TiC in-situ reinforced Ti750 matrix composite had the best microhardness value among all the materials.Its microhardness was as high as 1164.1 HV.（3）The effect of solid solution and solution aging process on the microstructure and properties of composites prepared by SPS process were studied.The results from both heat treatments show that the phase composition of the matrix and composite materials did not change,and the samples are still mainly composed ofα-Ti and SiC in the ex situ reinforced samples andα-Ti,TiC,SiC,and Ti₅Si₃ in the in-situ composite.The solid solution and aging process do not change the phase composition of the composite but enhances them.Under the solid solution process of 1010℃/3h/AC,the enhanced phase content is the highest and the strengthening effect is the best.The microhardnesses of the TiC in-situ reinforced Ti750 composite material after solid-solution at 1010℃/3h/AC and solution aging at 1010℃/3h/AC+750℃/8h/AC has the highest in both treatments with 1277.1 HV and 1171.5 HV,respectively.（4）The high temperature oxidation resistance of composites after solution and aging treatment was studied.The results show that the oxidation products of the composites oxidized at 800℃ for 100h are similar and they are mainly composed of TiO₂,Al₂O₃ and SiO₂.The average oxidation rate k⁺value of the composites are less than 1g·m^-2·h^-1,which is within the oxidation resistance level.With the addition of particulate reinforcements,the oxidation resistance was improved.The minimum oxidization weight gain was obtained in the TiC in-situ reinforced Ti750 matrix composite with a value of 3.0 mg.cm^-2.The oxide film is flat and dense.Cracking and pores are well combined with the matrix,and the oxidation resistance of this material is the best.（5）The hot corrosion resistance of composites after solution and aging treatment was studied.The results show that with the addition of particulate reinforcement,the corrosion resistance of the material decreases and the corrosion weight gain of the materials decreases.The corrosion gain of the composite prepared by adding 5vol.%SiCp has the least weight gain among the composites with 5.1 mg.cm^-2,which are 36.17%of the base alloy,indicating that the added SiCp can improve the hot corrosion resistance of the material.The corrosion products of the materials are similar under the same temperature,and are mainly composed of TiO₂,Al₂O₃,SiO₂,Na₂TiO₃,and Al₂TiO₅.In summary,this dissertation creatively used SPS processes to prepare particle-reinforced titanium-based composites by ex-situ reinforcement of SiCp,SiCw,B₄C,and GPLs with the matrix Ti750 alloy（new high temperature resistant titanium alloy）,and by in-situ reinforcedment of TiC by reactions between SiCp and the matrix Ti750 alloy,which provides a reference for the design and preparation of titanium matrix composites.The in-situ TiC reinforced Ti750 composite has the best properties,and solution aging treatment it at 1010℃/3h/AC+750℃/8h/AC enhances these properties significantly.