Study On Microstructure And Mechanical Properties Of Titanium Matrix Composite Bar Fabricated By Hot-canning Extrusion

Titanium matrix composites have wide application for aerospace and military owing to their high specific strength,excellent wear resistance and corrosion resistance.Their fabrication techniques are usually based on hot isostatic pressing, reaction hot pressing and spark plasma sintering process.However, the defects of complicated preparation technology, expensive facilities and low efficiency severely limit their wider application. Further investigation was focused on the early stage of the hot extrusion process on Ti Bw/Ti-6Al-4V composites bars,high temperature short time pre-sintering and hot extrusion process is proposed.Further optimization for the fabrication techniques of Ti Bw/Ti-6Al-4V composites bars has been achieved.In addition, the effect of extrusion temperature and boron additions on microstructure and mechanical properties has been studied.In this study, Ti Bw/Ti-6Al-4V composites bars based on high temperature short time pre-sintering and hot extrusion process have been fabricated.The short-time presintering at 1200℃ accelerated the reaction,increased the density of material and the efficiency.The ductility at room temperature of material was increased markedly. When the extrusion temperature were 1050℃ and 1150℃,the ductility were 5.08% and 7.83%,respectively,reaching the desired goal.Further investigation was focused on the effect of extrusion temperature on the microstructure and performance of Ti Bw/Ti-6Al-4V composites,and the relationship between temperature and mechanical properties was also studied.The studied temperature was chosen at 950℃~1150℃,and the pre-sintering temperature and time were 1200℃ and 0.5h,respectively.The quantity of Ti B whiskers declined with the increasing extrusion temperature,and the aspect ratios of Ti B whiskers were increased markedly.The elongated α grain in matrix translated into α colonies and boundary α gradually,and the quantity of β grain was also increased. When the extrusion temperature reached to 950℃,the <1010> texture in matrix was remarkably,and the corresponding tensile strength was 1191.2Mpa.When the temperature was increased to 1050℃,the matrix showed <0001>and<1010>texture,the tensile strength was 1171.8Mpa. When the extrusion temperature reached to 1150℃, the corresponding tensile strength was 1156.3Mpa.Their ductility were 2.32%,5.08% and 7.83%,respectively.By comparison,it is found that boron assitions refined the α-Ti remarkably and the α lamella neighboring Ti B whiskers globularized markedly. When the temperature was increased to 950 ℃,the deformation occured in the(α+β) phase field.Boron additions advanced the β transus remarkably,bring a higher texture intension of <1010> for the initial α-Ti.