An investigation of the deformation mechanism in grain size-sensitive Newtonian creep

• Published in: Acta materialia Vol. 48; no. 7; pp. 1517 - 1531
• Main Author: Wang, J.N
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 19.04.2000; Elsevier Science
• Subjects: Applied sciences; Condensed matter: structure, mechanical and thermal properties; CREEP; DIFFUSION; Exact sciences and technology; GRAIN BOUNDARIES; GRAIN SIZE; MATERIALS SCIENCE; MATHEMATICAL MODELS; Mechanical and acoustical properties of condensed matter; Mechanical properties of solids; Metals. Metallurgy; Physics; POLYCRYSTALS; STRAIN RATE; STRESSES; Grain boundaries; Creep; Diffusion; Grain boundary slide; Theoretical study; Polycrystals; Mechanical properties; Modelling; Property structure relationship; Creep deformation; Deformation law
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/S1359-6454(99)00450-4

Creep of polycrystalline materials at low stresses often shows a linear relationship between strain rate and stress, and an inverse dependence on grain size squared or cubed. Attribution of this behavior to diffusional creep or grain boundary sliding (GBS) has evoked much confusion and controversy in the literature. A model is proposed to unify these two creep mechanisms. The model predicts a change in dominant mechanism from diffusional creep to GBS accommodated mainly by diffusion or by GBS itself as the amount of matter moved by diffusion decreases. Corresponding to this change, the model also predicts a spectrum of creep rate with the absolute value being dependent upon the extent of diffusion accommodation. Although experimental data exhibit scattering, most of them are in very good agreement with the prediction of the GBS model. Therefore, it is suggested that the Newtonian creep behavior with grain size dependence be induced by GBS rather than by conventional diffusional creep as believed before.