Pure and ultra-fine grained Titanium for biomedical applications

A high strength to weight ratio, corrosion resistance and biocompatibility are properties which have made Ti-alloys the preferred metallic material for medical implants/prostheses. Depending on the type of implant, these alloys range from highly ductile a nd commercially pure variants, where a high formability is essential, to variants with a high strength (>1300 MPa). For most orthopaedic implants the alloy Ti-6Al-4V, considered to be chemically inert, compatible with human tissue and resistant to corrosi on by human body fluids, is applied. However, as normal wear can lead to deterioration of the implant and the subsequent release of potentially toxic vanadium and aluminium into the body, it would be beneficial to replace alloys like Ti-6Al-4V with as pur e variants as possible. Normally, the strength of pure Ti is less than half the strength of Ti-6Al-4V alloy and therefore too weak for prostheses that must bear heavy loads (e.g. leg or hipbone implants). In Tibia it will be attempted to produce pure and ultra-fine grained (UFG) Ti with strengths equal to or even higher than Ti-6Al-4V by severe plastic deformation (SPD). By subsequently performing carefully designed annealing treatments, specific high strength - high ductility combinations can be achieve d, and potentially UFG-Ti may therefore replace several of the currently applied Ti-alloys. In order to achieve this goal, however, it is essential to completely control the grain size development, which in turn makes it necessary to increase the understa nding of the mechanisms behind the formation of metallic nanostructures and their behaviour during subsequent annealing. This understanding will be developed in Tibia, where complementary experimental techniques like in-situ synchrotron XRD, FE-SEM, HRTEM and nano- and micromechanical tests will be combined to customize material design and processing routes.