| Titanium matrix composites have great potentiality and wide application due to their lightweight, excellent wear resistance and high temperature durability. However, the defects of complicated preparation technology, high production costs and difficult plastic deformation severely limit its wider application. Therefore, exploring a preparation technology with high efficiency and low cost for titanium matrix composites is of great significance to promote the development of titanium matrix composites. In this study,2.6wt.%TiB2/Ti-6Al-4V composite powders were used as the starting materials to study low-energy milling process. Further investigation was focused on the effect of the pre-sintering and hot extrusion process (extrusion ratio of10.56:1) on the performance of titanium matrix composites bars with Φ12×220mm, In addition, the heat treatment of solution and aging as well as relationships between microstructure and mechanical properties was also studied.The milling processing results showed that: the roundness of Ti-6Al-4V matrix particles was better with the lower milling speed, the fine TiB2powders adhered onto the surface of the large Ti-6Al-4V more firmly with the longer time. Combined with the SEM and XRD analysis, the two raw marerials were low energy milled at the speed of100rpm with a ratio of milled media to material of5:1for8h in order to fabricate the titanium matrix composites with excellent plasticity and network microstructure.The effects of pre-sintering temperature and pre-sintering time on the microstructure and mechanical properties of titanium matrix composites fabricated by hot-canning extrusion were also investigated in the present work. The studied temperature and time of pre-sintering were900~1100℃and0.5~2.0h, respectively. With the pre-sintering temperature improved, the macro-defects, such as pores and tearing crack etal, were remarkably decreased, the interfacial bonding strength gradually increased and the tensile strength and elongation were greatly improved. When the pre-sintering temperature reached to1100℃, the length of TiB whiskers was remarkably increased. The corresponding tensile strength and elongation were1343MPa and3.64%, respectively. With the pre-sintering temperature of1100℃and the holding time extended to1.0h,2.0h, the tensile strengths of TiBw/Ti-6Al-4V fabricated by hot-canning extrusion were1347MPa and1351MPa, respectively. The corresponding elongations were4.51%and4.88%, respectively. When the pre-sintering temperature was improved to1200℃, the can used in hot-extrusion was broken. So, the selected pre-sintering process was1100℃/0.5h.In order to get better mechanical poperty, the heat treatment contains two steps: quenching and aging. The temperature and time of quenching were950~1100℃and30minutes, respectively. The temperature of aging was400~700℃for6h. The result showed that: with quenching temperature increased, the volume fraction of primary α was decreased and the original β grain was coarsened. When the quenching temperature was increased to1000℃, all the primary α phase turned into β phase and then transformed into martensite after quenching. With the improved quenching temperature, the tensile strength of composites was increased firstly and then decreased. The martersite phase decomposed into fine mixed microstructure (α+β phases) during the aging treatment. With the increased aging temperature, the tensile strength was decreased and the elongation was gradually increased. Overaging accured when aging temperature increased to700℃, so the tensile strength decreased to1289MPa, while the elongation increased to6.5%. After quenching treatment at1000℃and aging treatment at700℃, the high temperature (500℃) tensile strength reached to1107MPa and the elongation increased to14.88%. Compared with that of the matix Ti-6Al-4V, the service temperature was increased. |
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