Preparation of Ti-Nb-Zr-O biomedical alloys from elemental powders by field assisted sintering technique

Abstract

Manufacturing of orthopedic implants requires materials with high strength and simultaneously low elastic modulus to avoid stress shielding effect arising when a bone is in contact with implant made from stiff material. Ti-Nb-Zr-O beta Ti alloys are perspective materials for this application as they possess both high strength and low modulus and moreover, they contain solely biocompatible elements.

High content of Nb (around 30 wt %) provides beta stabilization and Zr content avoids formation of stiff omega phase, which causes embrittlement. Finally, oxygen atoms in the amount larger than 0.5 wt.% provide the required strength due to interstitial strengthening.

Optimization of the alloy composition is crucial for fine tuning of beta phase stability, which determines elastic modulus of the material. Several alloys with different composition were prepared by blended elemental powder metallurgy (BEPM) using field assisted sintering technique (FAST).

This approach can provide fast sampling of the alloy composition using low amount of input material. To achieve homogenization of chemical composition, sintering temperatures of 1400°C - 1500°C are needed for 15 - 30 min, despite significantly lower temperature would be sufficient for compaction.

Chemical homogeneity, phase composition, microstructure and mechanical properties of prepared materials were determined and several potential candidate alloys with strength exceeding 1000 MPa and elastic modulus as low as 60 GPa were selected.