Initial exploration of Ti–Ta, Ti–Ta–Ir and Ti–Ir alloys: Candidate materials for coronary stents

The objective of this study was to explore titanium alloys with increased elastic modulus and improved radiopacity, with a view to utilizing titanium in balloon-expandable coronary stents. Ti–50Ta, Ti–45Ta–5Ir and Ti–17Ir alloys were prepared using arc-melting techniques. Microstructural and tensile properties were evaluated in solution-treated conditions for each alloy, and also in aged conditions for the Ti–17Ir. An elastic modulus of 128 GPa was recorded for the Ti–17Ir alloy and this high value is attributed to the stiff Ti3Ir phase present in the eutectoid structure observed. The mechanical properties recorded, in addition to improved radiopacity, make the Ti–17Ir alloy more suitable for stent applications than commercially available titanium materials. Corrosion resistance and biocompatibility have not been assessed but the noble characteristics of iridium suggest that these aspects will be acceptable.