Effect of melt hydrogenation on microstructure evolution and tensile properties of (TiB + TiC)/Ti-6Al-4V composites

In order to fabricate in-situ synthetic (TiB + TiC)/Ti-6Al-4V composites, we conducted arc-smelting in the atmosphere of hydrogen and argon gaseous mixture using a melting casting method of melt hydrogenation technology. Some experimental parameters such as arc current, voltage, gas partial pressure and smelting time were precisely controlled. The molar ratio of the ceramic phase is 1:1 at a total integral of 5%. The microstructure evolution, tensile properties and fracture mechanism of the composite at room temperature are revealed and discussed. The results of the tensile test demonstrate that melt hydrogenation technology remarkably improves the ultimate strength of (TiB + TiC)/Ti-6Al-4V composites accompanied by slight increase of elongation, in which the 5 vol% (TiB + TiC)/Ti-6Al-4V increased by 15.19% from 901.42 MPa to 1038.42 MPa with elongation increasing from 0.47% to 0.78%, compared with that of the unhydrogenated composites. The improvement in the strength of the composite can be attributed to the refinement in matrix α layer and the increasement of the aspect ratio of TiB whiskers. The use of melt hydrogenation technology is found to change the trend of segregation of ceramic phase to primary β phase at grain boundaries into random dispersion distribution.