Processing of porous titanium niobium alloys for biomedical applications

In this study, pure Ti, pure Nb and spherical Mg elemental powders were used to produce Ti74Nb26 alloys having porosities in the range of 43-68% for biomedical bone replacement applications. Space holder technique combined with hot pressing was used to fabricate porous specimens for the first time. Firstly, Ti, Nb and different amount of Mg powders (40%, 50%, 60% and 70% by vol.) were mixed by hand for 15min. Mixed powders were then poured into hollow cylindrical graphite dies with inner diameter of 15mm and hot pressed at 600ºC for 1h to prevent melting of Mg (650°C) under a constant pressure of 50MPa to produce samples with a height of 10 mm and argon gas was used during production to prevent oxidation. After hot press samples were sintered in a vertical furnace at 1200°C for 4h under flowing inert argon gas atmosphere. During sintering Mg also (Mg boiling point is 1090°C) was evaporated and removed from the samples and accordingly macro-pores were formed. X-Ray Diffraction and Scanning Electron Microscopy investigations showed that β phase was the main phase in the microstructure of all the samples. A small amount of α and pure Nb were also observed. Mechanical properties of the porous specimens were sufficient for cancellous bone replacement applications whereas not suitable for the cortical bone replacements. Undesired micro-pores formed as a result of inefficient hot pressing and inadequate sintering temperature caused poor mechanical properties.