Experimental and computational investigation of Ti-Nb-Fe-Zr alloys with limited Fe contents for biomedical applications

Among many β-metastable alloys explored for biomedical applications, alloys from the Ti-Nb-Fe-Zr system present great potential regarding cost and mechanical strength. In this article, we take a new look at the possibility of using Fe as a minor alloying element in the Ti-Nb-Fe-Zr system, with additions up to 2.0 wt% Fe. Additional compositions fixing the Nb/Fe ratio and changing Zr content from 7–13 wt% were also explored, resulting in a total of five different alloys. The samples were solution-treated and then subjected to three different conditions: water-quenched, furnace-cooled, and step-quenched to 450 ºC for 12 h. Resultant microstructures were analyzed using X-ray diffraction, differential scanning calorimetry, scanning, and transmission electron microscopy. DSC experiments indicate that Zr might alter the phase transformations that occur during heating and cooling cycles. First-principles calculations confirmed that Zr's addition is crucial to reduce the elastic modulus of the β matrix and increase the ω-phase formation energy relative to β. All alloys presented mechanical properties suitable for biomedical applications; however, Ti-23Nb-2.0Fe-10Zr (wt %) stands out with the best combination of mechanical strength and elastic modulus after aging.