Mechanical properties of Ti-6Al-4V/TiB composites with randomly oriented and aligned TiB reinforcements

Abstract

In situ Ti-6Al-4V/TiB discontinuously reinforced composites, containing 20 and 40% of TiB whiskers by volume, were produced by blending Ti, Al/V, and TiB 2 powders. The consolidated powder blends were annealed to transform the TiB 2 particles to TiB. The microstructural evolution of the composite was studied as a function of heat treatment duration at 1100, 1200, 1300 and 1400 °C. The mechanical properties of Ti-6Al-4V/TiB composites were established in tension and compression at room temperature and 300 °C, and by resonant ultrasound spectroscopy (RUS), for the two volume fractions of TiB, and for randomly oriented and aligned arrays of TiB whiskers. The average Young’s modulus of the composite with 20% of randomly oriented TiB whiskers was 153 GPa, compared to 109 GPa for unreinforced Ti-6Al-4V. The average Young’s modulus of composites with 20 and 40% of aligned TiB whiskers was measured along the extrusion axis as 169 and 205 GPa, respectively. The stiffness of TiB whiskers was determined from bulk measurements with the Halpin-Tsai equation to be 482 GPa. Yield and ultimate strengths near 1200 MPa were measured. The strength and ductility of the materials were limited in the present study by non-optimal matrix microstructure and inadequate particulate distribution, and approaches for properties improvements are provided.