Journal Article Influence of applied tensile stress on formation and growth of ellipsoidal ω precipitates in a Ti-20wt%Mo alloy

Monzen, Ryoichi  ,  Kawai, Ryutaro  ,  Watanabe, Chihiro

The effects of tensile stress on the nucleation and growth of ellipsoidal ω phase precipitates have been investigated for a Ti-20wt%Mo alloy aged at 300 °C. Application of a tensile stress promotes not only the nucleation but also the growth of ω precipitates. Estimates of the average misfit strains along the loading and the transverse directions from measurements of the length change reveal the preferential formation of specific ω variants among crystallographicallyequivalent four ones. The average size of the precipitates in the alloy aged under no stress follows initially a parabolic growth law, whereas when aged under a tensile stress of 400 and 450MPa the precipitate size increases linearly with aging time, this fact indicating that while the growth of ω precipitates is governed by diffusion of Mo from the ω/β interface to the β matrix under no stress, precipitate growth is instead interface-controlled under tensile stress.

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