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Can local hot spots induce α2/γ lamellae during incomplete massive transformation of γ-TiAl alloys?

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Fischer, F. D., Cha, L., Dehm, G., & Clemens, H. J. (2010). Can local hot spots induce α2/γ lamellae during incomplete massive transformation of γ-TiAl alloys? Intermetallics, 18(5), 972-976. doi:10.1016/j.intermet.2010.01.017.


Cite as: http://hdl.handle.net/11858/00-001M-0000-0024-56B0-A
Abstract
Oil quenching is applied to a Ti-45Al-7.5b alloy (in at%) in order to investigate the occurrence of local ‘‘hot spots’’ during rapid cooling from the single a-phase region. After quenching the microstructure consists of large a2-Ti3Al grains and a small volume fraction of massively transformed gm-TiAl particles. The majority of the gm-particles show a featureless a2/gm interface, whereas in the immediate vicinity of some gm-particles lamellar a2/g-structures exist, exhibiting a Blackburn orientation relationship. The extension into the a2-parent grain is in the range of 1–10 µm. In this study it is investigated, if the diffusion-controlled formation of the g-laths is triggered by the release of latent heat during the a/gm transformation, which leads to a local increase in temperature by a hot spot effect. A theoretical model is presented, which describes the temperature conditions around the hot spot. The model predicts that the life time of the hot spot is much too short to generate g-laths observed with a length of 1–10 µm.