On the athermal nature of the β to ω transformation

Dutta, Jayanta ; Ananthakrishna, G. ; Banerjee, S. (2012) On the athermal nature of the β to ω transformation Acta Materialia, 60 (2). pp. 556-564. ISSN 1359-6454

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Official URL: http://www.sciencedirect.com/science/article/pii/S...

Related URL: http://dx.doi.org/10.1016/j.actamat.2011.10.005


One characteristic feature of the athermal α →ω transformation is the short time scale of the transformation. So far, no clear understanding of this issue exists. Here we construct a model that includes contributions from a Landau sixth-order free energy density, kinetic energy due to displacement, and the Rayleigh dissipation function to account for the dissipation arising from the rapid movement of the parent-product interface during rapid nucleation. We also include the contribution from ω-like fluctuations to local stress. The model shows that the transformation is complete on a time scale comparable to the velocity of sound. The estimated nucleation rate is several orders higher than that for diffusion-controlled transformations. The model predicts that the athermal ω phase is limited to a certain range of alloying composition. The estimated nucleation rate and the size of "isothermal" particles beyond 17% Nb are also consistent with experimental results. The model provides an explanation for the reprecipitation process of the ω particles in the "cleared" channels formed during deformation of ω-forming alloys. The model also predicts that acoustic emission should be detectable during the formation of the athermal phase.

Item Type:Article
Source:Copyright of this article belongs to Elsevier Science.
Keywords:Athermal Phase; Isothermal Phase; Omega Phase; β→ω Transformation
ID Code:91312
Deposited On:18 May 2012 07:29
Last Modified:18 May 2012 07:29

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