Enhancement of mechanical properties and shape memory effect of Ti-Cr-based alloys via Au and Cu modifications

Promoted mechanical properties and functionalities via Ta-tailored Ti-Au-Cr shape memory alloys towards biomedical applications

In view of the urgent demands of shape memory alloys (SMAs) for biomedical applications due to the world population aging issue, the mechanical properties and functionalities of the biocompatible Ti-Au-Cr-based SMAs, which are tailored by Ta additions, have been developed in this study. The quaternary SMAs were successfully manufactured by physical metallurgy techniques and their mechanical properties and functionalities were examined. In the continuous tensile tests, it was found that the correlation between the yielding strength and phase stability followed a typical trend of mechanical behavior of SMAs, showing the lowest yielding strength at the metastable β-parent phase. Functional mappings between the alloy strength and elongation revealed that compared to the Ta-free specimen, the ductility was promoted 50% while the strength remained intact through the 4 at.% introduction of Ta. Slight shape recovery was observed in the cyclic loading-unloading tensile tests during the unloading process and the highest shape recovery was found in the Ti-4 at.% Au-5 at.% Cr-4 at.% Ta specimen. This indicates that the 4 at.% Ta tailored Ti-Au-Cr SMAs could be a promising material for biomedical applications.

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

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.