Evaluation of the microstructures, strengthening mechanisms and corrosion behaviors of TiB2 powder added to Ti-8Ta-6Ni alloys through the vacuum sintering process

In the research, four different powders are mixed and used to produce Ti-8Ta-6Ni-xTiB(2) (x = 1, 3 and 5 mass%) alloys in three different proportions: Ti-8Ta-6Ni-ITiB2, Ti-8Ta-6Ni-3TiB(2) and Ti-8Ta-6Ni-5TiB(2). Moreover, the Ti-8Ta-6Ni-xTiB(2) alloys simultaneously undergo a vacuum sintering process at temperatures of 1250, 1275 and 1300 degrees C, respectively. The experimental results indicated that when 3 mass% TiB 2 was added to the Ti-8Ta-6Ni alloys, the specimen possessed optimal mechanical properties after sintering at 1275 degrees C for 1 h. The relative density reached 99.06%, hardness was enhanced to 68.18 HRA and transverse rupture strength (TRS) increased to 1454.64 MPa, respectively. Meanwhile, the optimal sintered-alloys have the lowest corrosion current (I-co(rr) = 6.42 x 10(-6) A cm(-2)) and highest polarization resistance (R-p = 6.81 x 10(3) Omega cm(2)) in 1 N H2SO4 solutions. The EBSD results showed that the boron atoms of the TiB2 powders produced an in situ reaction with titanium. Moreover, the orthorhombic TiB structure was uniformly dispersed in the titanium matrix, which was advantageous to the mechanical properties. The microstructure evolution of vacuum sintering Ti-8Ta-6Ni-xTiB(2) alloys reveals that the main strengthening mechanisms include dispersion strengthening, solid-solution strengthening and precipitation hardening. (C) 2020 Elsevier B.V. All rights reserved.