Investigations of Effects of Intermetallic Compound on the Mechanical Properties and Shape Memory Effect of Ti–Au–Ta Biomaterials

Abstract

Owing to the world population aging, biomedical materials, such as shape memory alloys (SMAs) have attracted much attention. The biocompatible Ti–Au–Ta SMAs, which also possess high X–ray contrast for the applications like guidewire utilized in surgery, were studied in this work. The alloys were successfully prepared by physical metallurgy techniques and the phase constituents, microstructures, chemical compositions, shape memory effect (SME), and superelasticity (SE) of the Ti–Au–Ta SMAs were also examined. The functionalities, such as SME, were revealed by the introduction of the third element Ta; in addition, obvious improvements of the alloy performances of the ternary Ti–Au–Ta alloys were confirmed while compared with that of the binary Ti–Au alloy. The Ti3Au intermetallic compound was both found crystallographically and metallographically in the Ti–4 at.% Au–30 at.% Ta alloy. The strength of the alloy was promoted by the precipitates of the Ti3Au intermetallic compound. The effects of the Ti3Au precipitates on the mechanical properties, SME, and SE were also investigated in this work. Slight shape recovery was found in the Ti–4 at.% Au–20 at.% Ta alloy during unloading of an externally applied stress.

A Review of Investigations on Microstructure and Mechanical Properties of the Present Achievements of the Ti-Au-based Shape Memory Alloys

“…Sc was ruled out due to its high price and high tendency to be oxidized, 36) while Zn was not considered owing to the same oxidation issue as Sc and its low boiling point, which makes the manipulation of the chemical composition of the alloys to be difficult. 37) Besides to the aforementioned 3d transition metals, 29) some of the 4d and 5d elements, such as Mo 29) and Ta, 38) were also focused. Mo is also an essential dietary element for the human body and it is used as a fundamental element for the calculation of the phase stability (i.e., the Mo equivalent).…”

“…On the other hand, since Ta is known as a weak β-stabilizer, 46) the addition concentration of Ta to the Ti-4Au alloy was thus determined to be 20 at.% and 30 at.%, respectively. 38) 2.2.1. Determination of the Cr as the Third Addition Element As shown in Fig.…”

“…As above-mentioned, Ta was also screened 38) and the results of the mechanical properties are shown as Fig. 2.…”

“…52,53) Furthermore, obvious two-stage yielding (i.e., stress plateau) could also be found in the stress-strain curve of the (a) Ti-4Au-20Ta alloy. The first stage yielding could be attributed to the stress-induced martensitic transformation (SIMT) since this alloy was composed of the metastable parent β-phase 38) while the second stage yielding corresponds to the plastic deformation (i.e., slip of dislocations). 54,55) On the other hand, the (b) Ti-4Au-30Ta alloy showed improved strength compared to the (a) Ti-4Au-20Ta alloy, and this could be ascribed to the precipitates of the Ti 3 Au compound.…”

Load-Independent Hardness and Indentation Size Effect in Iron Aluminides

“…These distinctive properties endow ICs with a range of unique applications, including hydrogen storage [2,3], catalysis [4,5], shape memory [6,7], superconductors [8,9], and structural applications [10,11]. Structural applications are especially advantageous when high-temperature-resistant components are required due to the high melting and disordering temperatures, high stiffness, and low diffusivity of ICs [10,11].…”