Processing of porous β-type Ti74Nb26 alloys for biomedical applications

Abstract

Ti74Nb26 alloys with porosities in the range of 45–68% were produced employing Mg space holder technique combined with hot pressing using elemental Ti, Nb and Mg powders. Powder mixtures were hot pressed at 600 °C (below the melting point of Mg, 650 °C) for 1 h under a constant pressure of 50 MPa and flowing argon gas. After hot pressing samples were sintered in a vertical furnace at 1200 °C (above the boiling temperature of Mg, 1090 °C) for 4 h under flowing inert argon gas atmosphere. Evaporation and removal of Mg particles from the samples were carried out during sintering simultaneously. X-ray diffraction and scanning electron microscopy analysis revealed that β phase was the main phase in the microstructure of all the samples. A small amount of α and undissolved pure Nb were also observed. Room temperature Young’s moduli and compressive strength of the specimens increased with decreasing porosity and were in the range of 1.6–14 GPa and 14–136 MPa, respectively. The mechanical properties of the 45%, 54% and 59% porous alloys were sufficient for both cortical and cancellous bone replacement applications. The alloy with a porosity content of 68% demonstrated mechanical properties suitable only for the cancellous bone implants.