Characterization of Ti6Al7Nb alloy foams surface treated in aqueous NaOH and CaCl2 solutions

Date

2016-07-01

Author

Butev, Ezgi
ESEN, ZİYA
Bor, Sakir

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Ti6Al7Nb alloy foams having 53-73% porosity were manufactured via evaporation of magnesium space holders. A bioactive 1 mu m thick sodium hydrogel titanate layer, NaxH2-xTiyO2y+1., formed after 5 M NaOH treatment, was converted to crystalline sodium titanate, Na2TiyO2y+1, as a result of post-heat treatment. On the other hand, subsequent CaCl2 treatment of NaOH treated specimens induced calcium titanate formation. However, heat treatment of NaOH-CaCl2 treated specimens led to the loss of calcium and disappearance of the titanate phase. All of the aforementioned surface treatments reduced yield strengths due to the oxidation of the cell walls of the foams, while elastic moduli remained mostly unchanged. Accordingly, equiaxed dimples seen on the fracture surfaces of as-manufactured foams turned into relatively flat and featureless fracture surfaces after surface treatments. On the other hand, Ca- and Na-rich coating preserved their mechanical stabilities and did not spall during fracture. The relation between mechanical properties of foams and macro-porosity fraction were found to obey a power law. The foams with 63 and 73% porosity met the desired biocompatibility requirements with fully open pore structures and elastic moduli similar to that of bone. In vitro tests conducted in simulated body fluid (SBF) showed that NaOH-heat treated surfaces exhibit the highest bioactivity and allow the formation of Ca-P rich phases having Ca/P ratio of 1.3 to form within 5 days. Although Ca-P rich phases formed only after 15 days on NaOH-CaCl2 treated specimens, the Ca/P ratio was closer to that of apatite found in bone.

Subject Keywords

Simulated body fluid, Hydrothermal treatment, Mechanical properties, Ti6Al7Nb alloy foam

URI

https://hdl.handle.net/11511/66593

Journal

JOURNAL OF THE MECHANICAL BEHAVIOR OF BIOMEDICAL MATERIALS

DOI

https://doi.org/10.1016/j.jmbbm.2015.12.040

Collections

Department of Metallurgical and Materials Engineering, Article

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Citation Formats

E. Butev, Z. ESEN, and S. Bor, “Characterization of Ti6Al7Nb alloy foams surface treated in aqueous NaOH and CaCl2 solutions,” JOURNAL OF THE MECHANICAL BEHAVIOR OF BIOMEDICAL MATERIALS, pp. 127–138, 2016, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/66593.