Use of TiH2 as a reactant in combustion synthesis of porous Ti5Si3 and Ti5Si3/TiAl intermetallics

Porous Ti5Si3 and Ti5Si3/TiAl intermetallics were fabricated by self-propagating high-temperature synthesis (SHS) from elemental powder compacts with addition of TiH2. The TiH2 content ranged from 1.25 to 6.25 mol.% for formation of the Ti5Si3 monoliths and from 2 to 10 mol.% for the Ti5Si3/TiAl composites. Due to endothermic decomposition of TiH2, the increase of TiH2 decreased the reaction temperature and combustion wave velocity. Moreover, dehydrogenation of TiH2 released hydrogen gas to act as a pore-forming agent and generated highly reactive Ti to facilitate the reaction. The porosity of the intermetallic product increased with increasing TiH2 content and the microstructure with a uniform distribution of pores was attained. As a consequence, the porosity of as-synthesized Ti5Si3 monoliths was controllable and increased from 38% to 60% with TiH2 additions. Likewise, Ti5Si3/TiAl composites with an increasing porosity from 31% to 56% were obtained from the TiH2-added samples.