Study On Microstructure And Properties Of In Situ Preparation TiB/Ti Matrix Composites

Pure Ti and its alloys have attracted extensive attention of many scientific researchers for their advantages of light weight and high strength,and are widely used in aerospace and other fields.However,when the working environment temperature of pure Ti and its alloys reaches 300～650℃,their high temperature properties are significantly reduced,which seriously restricts the using temperature range of pure Ti and its alloys.In order to improve this disadvantage and increase the service temperature of pure Ti and its alloys,the addition of reinforcing phase to prepare TMCs is now a common means to improve the high-temperature properties of titanium alloy materials.In this paper,a Ti-TiB₂composite powder with TiB₂particles uniformly adhering to the surface of pure Ti powder was prepared by combining the"200r/min+5:1+5h"ball milling parameters with the"forward and reverse+up and down"ball milling process.Then,the microstructure and mechanical properties of TiB/Ti matrix composites prepared by in-situ reaction at different SPS processes（1000℃,1100℃and 1200℃,60MPa,15min）were studied.After comprehensive consideration,the optimum SPS process was obtained:sintering temperature 1100℃,sintering pressure 60 MPa,holding time 15 min.The law of densification process of Ti-3wt%TiB₂composite powder during SPS cold pressing and SPS process was analyzed by MSC.Marc finite element software and compared with the relative density of TiB/Ti matrix composites prepared in situ at different SPS temperatures.The results show that the relative density distribution of the powder green body simulated by SPS 60MPa cold pressing was uneven,the minimum relative density value was 77.61%,and the maximum relative density value was 81.85%.The simulation results of the relative density of the samples prepared in situ by different SPS processes increased with the increase of SPS temperature.Compared with the experimental datas,the differences were only 0.28%,0.18%and 0.18%,and the coincidence was very good,indicating that the accuracy of the finite element simulation results was high.The microhardness,tensile strength at room temperature and tensile strength at 300℃of the TiB/Ti matrix composites prepared with different amounts of TiB₂reinforced particles were tested.The results showed that the average microhardness of the samples prepared by the composites increased with the increase of the amount of TiB₂reinforced particles,and the average microhardness of TMC-10 was the largest,reaching 316.478HV,which was 102.175%higher than that of pure Ti.However,the tensile strength of sintered samples showed a trend of increasing first and then decreasing.When the addition of TiB₂reinforced particles was 5 wt.%,the tensile strength of TMC-5 at room temperature and300℃were the best,which were 760.972MPa and 367.493MPa respectively.