Directional design and preparation of Ti-Nb based alloys with predicted high strength and low modulus for biomedical applications: Insights from first-principles calculations

Abstract

This paper presents the design of β-type Ti-Nb based alloys characterized by high strength and low modulus for biomedical applications. We used a Python program that applied the d-electron alloy design method and the valence electron concentration e/a method to suggest Ti-Nb based ternary alloys with specific desired characteristics, and then determined the modulus of these alloys through first-principles calculations and experimental investigations. The theoretic predication indicated that Ti₁₂Nb₃Zr₁ and Ti₁₂Nb₃Ta₁ as-cast were metastable β titanium alloys with good ductility even after 90 % cold deformation and a high elastic allowable strain (R_eH/E). The higher dislocation density led to a higher strength of the alloys. The formation of {111}<112>γ-fiber texture and {112}<111> slip was beneficial for the alloys to maintain characteristic low modulus. The experimental results showed that the elastic modulus of Ti₁₂Nb₃Ta₁ following cold rolling was slightly higher than that theoretically predicted. This discrepancy could be attributed to the formation of the α" phase with high modulus. It was also confirmed that the stable crystal structure of the simulated β-type Ti-Nb based alloy could be ensured during significant deformation under the experimental conditions, and this stability was dependent on the bonding capacity of the inner electrons. Thus this study offers both theoretical and experimental support for the fabrication of Ti-Nb based alloys that are designed with characteristic low modulus and high strength as novel orthopedic implants materials.