Effect of the Ti/Ta ratio on the feasibility of porous Ti25+x-Nb25-Zr25-Ta25-x (X= 0, 5, and 10) alloys for biomedical applications.

Abstract

Non-toxic biomedical HEAs by powder metallurgy methods have been scarcely studied despite their promising mechanical and biological behaviors. This work studied the microstructural, mechanical, electrochemical, and ion release effects of the Ti/Ta ratio on three porous Ti–Nb–Zr–Ta (TNZT) alloys. The microstructure of the TNZT alloys consisted of semi-equiaxed and micrometric BCC-phases (matrix) with lower contents of HCP phase. Elastic moduli (82–91 GPa), hardness (373–430 HVN), ultimate bending (225–475 MPa), and tensile (119–256 MPa) strength, electrochemical corrosion (4.5–9.6 μm year−1), and ion release (toxicity, 0.9–1.1 μm year−1) were within acceptable limits for implant biomaterials. Increasing the Ti content (and decreasing Ta) was advantageous for improving mechanical strengthening and reducing the elastic modulus. The medium value of elastic modulus may be beneficial to reduce the mechanical mismatch between the implant and the organic tissue. However, the corrosion rate and metallic ion release increased as a function of the Ti content. Besides, the alloy with the lowest Ti content (highest Ta content) showed local corrosion. Based on the above, the porous TNZT alloys with medium and highest Ti contents (30 and 35 wt%) were demonstrated as promising candidates for biomedical implant applications.