MECHANICAL PROPERTIES AND MICROSTRUCTURE OF PM Ti-Si_3N_4 DISCONTINUOUS FIBRE COMPOSITE

摘要

2 vol% Si_3N_4 fiber Ti composites were manufactured by uniaxially pressing the powders and subjecting the green compact to pressureless sintering at 1400°C in flowing argon. The resulting composites were >98% theoretical density. The hardness of the titanium composite was measured at HBW 401 compared to HBW 293 for pure titanium. Microstructural analysis showed clearly defined 200-300nm diameter crystalline fibers throughout the composite with a 2-4μm reaction boundary cementing them to the titanium. Concentrations of smaller Si_3N_4 particles were located at the titanium gi'ain boundaries, which may have reacted to fonn Ti-Si-N phases. The improved mechanical properties might be from a combination of discontinuous fiber reinforcement, nitrogen addition to the Ti matrix, and grain-boundary reinforcement.