Non-classical Homogeneous Precipitation Mediated by Compositional Fluctuations in Titanium AlloysActa Materialia (2012)
This paper presents experimental evidence of homogeneous precipitation of the α-phase within the β matrix of a titanium alloy, and then accounts for this phase transformation by a new, non-classical mechanism involving compositional fluctuations, based on the pseudo-spinodal concept . This mechanism involves local compositional fluctuations of small amplitude which, when of a certain magnitude, can favor thermodynamically certain regions of the β matrix to transform congruently to the α-phase but with compositions far from equilibrium. Subsequently, as measured experimentally using the tomographical atom probe, continuous diffusional partitioning between the parent β- and product α-phases during isothermal annealing drives their compositions towards equilibrium. For a given alloy composition, the decomposition mechanism is strongly temperature dependent, which would be expected for homogeneous precipitation via the compositional fluctuation-mediated mechanism but not necessarily for one based on classical nucleation theory. The applicability of this mechanism to phase transformations in general is noted.
- Nucleation of phase transformations,
- Titanium alloys,
- Atom probe tomography (APT),
Citation InformationS. Nag, Y. Zheng, R.E.A. Williams, A. Devaraj, et al.. "Non-classical Homogeneous Precipitation Mediated by Compositional Fluctuations in Titanium Alloys" Acta Materialia Vol. 60 Iss. 18 (2012) p. 6247 - 6256
Available at: http://works.bepress.com/peter-collins/5/