Microstructure and mechanical properties of in situ synthesised (TiC+TiB)/Ti-6Al-4V composites prepared by powder metallurgy

Titanium matrix composites (TMCs) reinforced with hybrid reinforcements were synthesised by blending Ti-6Al-4V, Ti, B4C and C powders followed by reactive hot pressing. The phases were identified by X-ray diffraction, and the microstructures were examined by optical microscopy and scanning electron microscopy (SEM). Mechanical properties were tested at room temperature (RT), 400, 450 and 500 degrees C respectively. The results show that Ti-6Al-4V produced by hot pressing has higher strength and better plasticity than by casting; there are four kinds of reinforcements in TMCs, and the TMCs' strength increases significantly with the addition of reinforcements both at RT and elevated temperature; the TMCs with 5 vol.-% of reinforcements have higher strength than that with 10 vol.-% at high temperature. The fracture surfaces were examined by SEM. It shows that the bond between the reinforcements and matrix is not so well that reinforcements' debonding occurs even at RT.