Effect of α-precipitation on the superelastic behavior of Ti–40 wt.%Nb–0.3 wt.%O alloy processed by equal channel angular extrusion
✍ Scribed by R. Arockiakumar; J.K. Park
- Publisher
- Elsevier Science
- Year
- 2010
- Tongue
- English
- Weight
- 510 KB
- Volume
- 527
- Category
- Article
- ISSN
- 0921-5093
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✦ Synopsis
A ultrafine-grain-structured Ti-40Nb-0.3O (wt.%) alloy has been fabricated via equal channel angular extrusion (ECAE) followed by annealing within an ␣ +  two-phase field. The precipitation of ␣-phase was responsible for producing an annealed ultrafine-grain structure of about 1 m. As-ECAEed specimen showed a large recovery strain of 3.5% at -125 • C, although no superelastic property was observed. Postannealing of the ECAEed specimen led to a recovery of superelastic behavior. The superelastic strain first increased and then decreased with annealing time. A maximum superelastic strain of 2.5%, on subjecting 896 MPa, was observed at -125 • C. The increase of superelastic strain during the initial stage of annealing was due to the precipitation of ␣-phase leading to oxygen depletion in -matrix. The precipitation of ␣phase also led to a decrease of critical stress for stress induced martensitic transformation and to an increase of critical stress for slip.