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. 2016 Jul 20;2(7):e1600319.
doi: 10.1126/sciadv.1600319. eCollection 2016 Jul.

High hardness in the biocompatible intermetallic compound β-Ti3Au

Eteri Svanidze  1 , Tiglet Besara  2 , M Fevsi Ozaydin  3 , Chandra Sekhar Tiwary  4 , Jiakui K Wang  1 , Sruthi Radhakrishnan  4 , Sendurai Mani  5 , Yan Xin  2 , Ke Han  2 , Hong Liang  3 , Theo Siegrist  2 , Pulickel M Ajayan  4 , E Morosan  6
Affiliations

High hardness in the biocompatible intermetallic compound β-Ti3Au

Eteri Svanidze et al. Sci Adv. .

Abstract

The search for new hard materials is often challenging, but strongly motivated by the vast application potential such materials hold. Ti3Au exhibits high hardness values (about four times those of pure Ti and most steel alloys), reduced coefficient of friction and wear rates, and biocompatibility, all of which are optimal traits for orthopedic, dental, and prosthetic applications. In addition, the ability of this compound to adhere to ceramic parts can reduce both the weight and the cost of medical components. The fourfold increase in the hardness of Ti3Au compared to other Ti-Au alloys and compounds can be attributed to the elevated valence electron density, the reduced bond length, and the pseudogap formation. Understanding the origin of hardness in this intermetallic compound provides an avenue toward designing superior biocompatible, hard materials.

Keywords: Biocompatible alloys; coefficient of friction; elevated electron density; gold alloys; hardness; medical applications; metals; pseudogap; titanium alloys; titanium gold alloys.

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Figures

Fig. 1
Fig. 1. Hardness of Ti1−xAux and other intermetallic alloys and compounds.
Hardness as a function of x (top axis) or mass density ρ (bottom axis) in Ti1−xAux. Blue squares, medical alloys; green triangles, intermetallic compounds.
Fig. 2
Fig. 2. Structural analysis of the Ti0.75Au0.25 alloy.
(A) Crystal structure of the α-Ti3Au phase along with the cuboctahedron local environments of the Au (left inset) and Ti (right inset) atoms. (B) Crystal structure of β-Ti3Au along with the icosahedron local environment of Au (left inset) and the 14-vertex Frank-Kasper polyhedron local environment of Ti (right inset). (C) XRD pattern was fitted with the β-Ti3Au phase (blue vertical symbols). Small inclusions of α-Ti3Au and α-Ti are marked by asterisks. arb. units, arbitrary units. (D and E) HRTEM (high-resolution transmission electron microscopy) images of the Ti0.75Au0.25 sample, taken for the [111] and [100] orientations, respectively. (F and G) SAD (selected area diffraction) images of the [111] and [102] orientations, respectively.
Fig. 3
Fig. 3. DOS of Ti–Au stoichiometric compounds.
DOS (solid lines) as a function of energy for β-TiAu (black), TiAu (yellow), TiAu4 (blue), and β-Ti3Au (red), with the pronounced valley around the Fermi energy in β-Ti3Au marked by a dotted line and highlighted in yellow (inset).
Fig. 4
Fig. 4. Wear analysis of Ti1−xAux alloys against a diamond-SiC disc.
(A) COF as a function of time for x = 0, 0.25, 0.30, and 0.50. Inset: An alumina container showing that Ti1−xAux adheres to this ceramic component. (B) Wear volumes of Ti1−xAux (dashed) compared to diamond-SiC (solid).
Fig. 5
Fig. 5. SEM images of pin and disc wear tests.
(A, C, E, and G) Ti reference ingot (A), Ti1−xAux pins for (C) x = 0.25, (E) x = 0.30, and (G) x = 0.50. (B, D, F, and H) Corresponding wear tracks on the diamond-SiC disc. Red rectangles (right panels) identify the regions of contact between the disc and the pin. For the (E) and (F) pair, there is little wear on both surfaces, indicating the wear resistance of the Ti0.75Au0.25 sample.
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References

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