M. González, F. J. Gil, J. M. Manero, Universitat Politècnica de Catalunya, Barcelona, Spain; J. Peña, Elisava Escola Superior de Disseny, Barcelona, Spain
Ideally, the elastic modulus of a biomaterial to be used in load transfer implants has to be similar to that of cortical bone (~27 GPa) in order to avoid the stress shielding effect. On the other hand, NiTi alloys are the only shape memory alloys which have been used as implantable materials in the human body. NiTi alloys have high damping capacity, high wear resistance and low elastic modulus, which are interesting properties for this kind of implants. However, the Ni ions release to the surrounding tissue generates adverse reactions.
The objective of the present work is to characterize the influence of cold work in the thermoelastic martensitic transformation and elastic modulus of two Ni-free Ti alloys in order to produce a new biomaterial for load transfer implants.
Microscopy and X-Ray Diffraction results showed the presence of stress induced martensite in the Ti-24.8Nb-16.2Hf-1Zr cold rolled alloy. Moreover, the nanoindentation tests with spherical tip showed a decrease of the elastic modulus when increasing the cold work percentage. The lowest value (46 GPa) was achieved after the 95% reduction in thickness. However, the Ti-35Nb-9Hf-1Zr alloy also has a low elastic modulus (58GPa) did not present evidences of thermoelastic martensitic transformation and neither a decrease of the elastic modulus.
Summary: The main objective of this work is to characterize the influence of cold work in the thermoelastic martensitic transformation and elastic modulus of two Ni-free Ti alloys in order to produce a new biomaterial for load transfer implants.
