Journal Article Tensile-stress-induced growth of ellipsoidal ω-precipitates in a Ti–20wt%Mo alloy

Monzen, Ryoichi  ,  Kawai, Ryutaro  ,  Oyama, Toru  ,  Watanabe, Chihiro

51 ( 5 )  , pp.2490 - 2498 , 2016-03-01 , Springer
The effects of applied tensile stress on the growth of ellipsoidal ω phase precipitates have been investigated for a Ti–20wt%Mo alloy aged at 300 °C. The application of tensile stress accelerates the growth of ω-precipitates when the misfit strain εΜ of the precipitates along the loading direction is greater than 0; however, it does not significantly affect the growth of precipitates in cases where εΜ < 0. Whereas the growth of precipitates under no stress or in the case where εΜ < 0 under tensile stress is governed by the diffusion of Mo from the ω/β interface toward the β-Ti matrix, precipitate growth is instead interface-controlled in the case where εΜ > 0 under a tensile stress of 400–550 MPa. The growth velocity of precipitates in the case where εΜ > 0 is proportional to the tensile stress. This result, together with the misfit strain dependence of the growth of precipitates, is discussed on the basis of the interaction energy between the stress acting on an ω-precipitate and its misfit strain. The activation energies for the diffusion-controlled and interface-controlled growth are estimated to be approximately 190 and 130 kJ/mol, respectively. The value of 190 kJ/mol is consistent with the activation energy for volume diffusion of Mo in β-Ti. © 2015 Springer Science+Business Media New York
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