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- Title
Phase transformation kinetics of ω-phase in pure Ti formed by high-pressure torsion.
- Authors
Adachi, Nozomu; Todaka, Yoshikazu; Irie, Kenshu; Umemoto, Minoru
- Abstract
High-pressure torsion (HPT) process is the only method which can obtain a 100 vol% of high-pressure ω-phase sample at ambient condition in pure Ti. In this paper, the mechanism of ω-phase stabilization by the HPT process is discussed on the basis of the reverse phase transformation kinetics of ω-phase in pure titanium formed by the HPT process and then measured using electrical resistivity and calorimetric experiments. The single ω-phase sample showed much higher electrical resistivity of 0.95 μΩ m at 350 K compared with that of the single α-phase sample (0.62 μΩ m). The ω-to-α reverse transformation behavior was clearly observed through both electrical resistivity and calorimetric measurements. The activation energy for ω-to-α reverse transformation, derived from the kinetics, showed a value close to that for the self-diffusion of Ti. The ω-phase obtained after the HPT process has an equiaxed submicron microstructure. The microstructure of reverse transformed α-phase showed no evidence of the occurrence of martensitic transformation. These results suggest that the mechanism governing ω-to-α phase transformation changed from diffusionless martensitic transformation to diffusion-controlled transformation after severe plastic deformation using the HPT process.
- Subjects
PHASE transitions; CHEMICAL kinetics; HIGH pressure (Technology); TITANIUM alloys; TORSION; CHEMICAL stability
- Publication
Journal of Materials Science, 2016, Vol 51, Issue 5, p2608
- ISSN
0022-2461
- Publication type
Article
- DOI
10.1007/s10853-015-9574-z