Selection of Ti Alloys for Bio‐Implants: An Application of the Ashby Approach with Conflicting Objectives

Abstract

The aim of the present work is to develop a materials selection strategy for biomedical Ti alloys by combining Ashby's method with a recently published dataset. The selection process concerns mechanical properties such as yield strength, elastic modulus, deformation at rupture, and the cost of the material. Outputs of the selection process point to alloys from both Ti‐Nb and Ti‐Mo systems as viable candidates for joint replacement materials. Additionally, this work discusses the crucial role of certain alloying elements in obtaining high elastic admissible strains, that is, a high yield strength‐to‐modulus ratio. Adding solutes such as Ta, Zr, Sn, Fe, and O is vital to stabilizing the β phase, suppressing the ω phase and increasing mechanical strength. Considering the minimum requirements of a 400 MPa yield strength, and 10% elongation at rupture, the best alloys identified via a multi‐objective optimization approach are Ti‐4.6Mo‐3.3Sn‐1.0Fe‐0.4O, Ti‐22.1Nb‐5Zr‐1.0Fe, and Ti‐20.3Nb‐4.7Ta‐2.5Sn (at%). These compositions present elastic moduli lower than 55 GPa, with an optimal trade‐off between a high elastic admissible strain and low cost. Updated property maps and analyses of conflicting properties are provided to support the conclusions.