A model for diffusional cavity growth in superplasticity

Chokshi, Atul H. ; Langdon, Terence G. (1987) A model for diffusional cavity growth in superplasticity Acta Metallurgica, 35 (5). pp. 1089-1101. ISSN 0001-6160

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Official URL: http://linkinghub.elsevier.com/retrieve/pii/000161...

Related URL: http://dx.doi.org/10.1016/0001-6160(87)90056-3


There is an enhancement in the diffusional growth of cavities in superplastic materials if the cavity size exceeds the grain size so that vacancies diffuse into the cavity along a number of grain boundary paths. A model for this process is developed, and it is shown that the rate of change of cavity radius with strain due to superplastic diffusion growth is given by dr/dε ~ -45Ω δDgb/d2kT (σ/ε) where r is the cavity radius, ε is the total strain, Ω is the atomic volume, δ is the grain boundary width, Dgb is the coefficient for grain boundary diffusion, d is the spatial grain size, k is Boltzmann's constant, T is the absolute temperature, σ is the applied stress and ε is the strain rate. Superplastic diffusion growth is therefore independent of the instantaneous cavity radius and inversely proportional to the square of the grain size; in practice, this process becomes important at the lower testing strain rates and when the specimen grain size is typically less than ~5 μm. It is demonstrated that the occurrence of superplastic diffusion growth is capable of providing an explanation for the experimental observations of large rounded cavities in several superplastic materials.

Item Type:Article
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ID Code:22402
Deposited On:25 Nov 2010 14:06
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