Fabrication and Properties of Porous NiTi Alloy by Gel-Casting with TiH₂ Powders

Porous NiTi alloys exhibit excellent properties for biomedical applications, but the existing processing techniques are expensive and difficult. In this study, gel-casting, a near-net-shape technique, is used to prepare porous NiTi from a slurry containing MAM as a monomer, Ni and TiH₂ powders as raw materials. The properties of the slurries and the sintered samples were characterized. The porous NiTi alloys with a porosity of 40-46% were fabricated by gel-casting a slurry with an ammonium citrate content of 1 wt.%, MAM concentration of 15-20 wt.%, and a solid loading of 42-45 vol.%, followed by sintering at temperatures from 1000-1050 °C for 2 h. The resulting alloys had compressive strengths of 100-200 MPa and elastic moduli of 13-17 GPa. The use of TiH₂ powder in the aqueous gel system prevented the formation of TiO₂ and TiC phases and helped to form the NiTi phase. This indicates that gel-casting is a promising technology for the fabrication of porous implants with complex shapes at low cost.