Effect of Quenching and Reheating on Isothermal Phase Transformation in Ti-15Nb-10Zr Alloy

Abstract:

Isothermal phase transformation in Ti-15Nb-10Zr (at%) alloys has been examined by mainly means of transmission electron microscopy. Specimens solution-treated at 1000°C in  phase field were directly held at temperatures between 350 and 450°C for 1.8-86.4ks, which are called "DH (direct holding)-specimen". On the other hand, some specimens solution-treated at 1000°C were quenched into iced brine and then aged at temperatures between 350 and 450°C, which are called "QA(quench and aging)-specimen". In the DH-specimen held at 400°C α phase formed in β matrix. Microstructure evolution of QA-specimen aged at 400°C, on the other hand, is as follows.  phase formed in β matrix after aging for 1.8ks and further aging led to growth of  phase. After prolonged aging, α phase started to form in β matrix. These experimental results indicate that process of the quenching and reheating promotes the formation of  phase. Specimen quenched into iced brine after solution treatment exhibited α'' phase formation. The α'' phase in the quenched specimen would transform into β phase during reheating to the aging temperature. Reversion process of α''  β phase could promote the formation of  phase in β. Microstructure formation in the DH- and QA-specimens at 350 and 450°C will also be explained.

• Periodical: Materials Science Forum (Volumes 638-642)
• Pages: 582-587
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.638-642.582
• Online since: January 2010
• Authors: Sengo Kobayashi, Ryoichi Ohshima, Kiyomichi Nakai, Tatsuaki Sakamoto
• Keywords: Biomaterial, Phase Transformation, TEM, Titanium Alloy, α Phase, Ω Phase

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