Abstract
In this work, different thermomechanical treatment conditions were used to improve the mechanical performances of Ti-25Nb-8Sn. During cold rolling treatment (50, 75, and 90 %), as-cast Ti-25Nb-8Sn underwent a stress-induced phase transformation from a single β phase to a three-phase structure of α'' + β + ω_str. After the subsequent aging treatment, Ti-25Nb-8Sn presents three-phase β + α'' + ω_iso (at 250 and 400 °C, for 30 min) and two-phase β + α (at 600 °C, for 30 min). At lower aging temperatures (250 and 400 °C), yield strength/modulus (× 1000) ratios of Ti-25Nb-8Sn are dramatically improved with a maximum increase of 143 %, from 9.06 (as-cast) to 16.2–22.0. Under various thermomechanical treatment conditions in this study, the results show that Ti-25Nb-8Sn has excellent yield strength/modulus (× 1000) ratio (∼ 22) and corrosion resistance after 90 % cold rolling and subsequent aging treatment at 250 and 400 °C for 30 min.

Key words
titanium alloys, biomaterials, cold working, aging, hardness

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