Characterization of Ti6Al7Nb alloy foams surface treated in aqueous NaOH and CaCl2 solutions.

Ti6Al7Nb alloy foams having 53-73% porosity were manufactured via evaporation of magnesium space holders. A bioactive 1µm thick sodium hydrogel titanate layer, NaxH2-xTiyO2y+1, formed after 5M NaOH treatment, was converted to crystalline sodium titanate, Na2TiyO2y+1, as a result of post-heat treatment. On the other hand, subsequent CaCl2 treatment of NaOH treated specimens induced calcium titanate formation.

Superelasticity and compression behavior of porous TiNi alloys produced using Mg spacers.

In the scope of the present study, Ni-rich TiNi (Ti-50.6 at %Ni) foams with porosities in the range 38-59% were produced by space holder technique using spherical magnesium powders as space formers. Single phase porous TiNi alloys produced with spherical pores were subjected to loading-unloading cycles in compression up to 250 MPa stress levels at different temperatures in as-processed and aged conditions.

Fatigue behavior of TiNi foams processed by the magnesium space holder technique.

While the wide range of applications of TiNi alloys makes them highly appealing due to their shape memory and superelasticity properties, the production of TiNi in the porous form further enlarges their application fields. Porous TiNi alloys have been studied extensively for biomedical applications since their elastic modulus is similar to that of bone. Accordingly, TiNi foams have been widely characterized in terms of their various mechanical properties; however, their fatigue properties have not been well studied, even though this is of vital importance in structural applications such as medical implants.