Achievement of Room Temperature Superelasticity in Ti-Mo-Al Alloy System via Manipulation of ω Phase Stability.

Wan-Ting Chiu,Naoki Nohira,Hideki Hosoda,Akira Umise,Masaki Tahara

doi:10.3390/ma15030861

Wan-Ting Chiu, Naoki Nohira + Show 3 more

Open Access

https://doi.org/10.3390/ma15030861

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Journal: Materials (Basel, Switzerland)	Publication Date: Jan 23, 2022
Citations: 3	License type: CC BY 4.0

Affiliation: Tokyo Institute of Technology

Abstract

The achievement of room-temperature (RT) superelasticity in a Ti-Mo-Al ternary alloy system through the addition of a relatively high concentration of Al to manipulate the phase stability of the ω phase is realized in this study. The composition of the Ti-6 mol% Mo (Ti-11.34 mass% Mo) alloy was designated as the starting alloy, while 5 mol% Al (=2.71 mass% Al) and 10 mol% Al (=5.54 mass% Al) were introduced to promote their superelastic behavior. Among the alloys, Ti-6 mol% Mo-10 mol% Al alloy, which was investigated for the very first time in this work, performed the best in terms of superelasticity. On the other hand, Ti-6 mol% Mo and Ti-6 mol% Mo-5 mol% Al alloys exhibited a shape memory effect upon heating. It is worth mentioning that in the transmission electron microscopy observation, ω phase, which appeared along with β-parent phase, was significantly suppressed as Al concentration was elevated up to 10 mol%. Therefore, the conventional difficulties of the inhibited RT superelasticity were successfully revealed by regulating the number density of the ω phase below a threshold.

Highlights

Shape memory alloys (SMAs) have been extensively investigated owing to their functional properties, such as shape memory effect (SME) and superelasticity
The β-Ti-based SMAs are considered as promising candidates for the biomedical and biomaterial communities due to the aforementioned functionalities (i.e., SME and superelasticity) and good biocompatibility [1,2]
The β-type Ti-Mo-Al system was prepared in this study for studying its superelasticity at room temperature (RT)

Summary

Introduction

Shape memory alloys (SMAs) have been extensively investigated owing to their functional properties, such as shape memory effect (SME) and superelasticity. Our group succeeded in developing RT superelasticity via MT temperature regulation by alloying Zr and Sn to Ti-3 mol% Mo specimens [9]. Ijaz et al discovered that stress hysteresis (∆σ) of superelastic Ti-Nb-Mo alloys was alleviated via Sn addition, which suppresses formations of the ω phase [17].

Results

Conclusion