Byung-Nam Kim*, Keijiro Hiraga*, Yoshio Sakka** and Byung-Wook Ahn***
* Mechanical Properties Division, National Research Institute for Metals, Tsukuba 305-0047 ** Advanced Materials Processing Division, National Research Institute for Metals, Tsukuba 305-0047 *** Department of Mechanical Engineering, Taejon National University of Technology, Taejon 300-717, KoreaThe enhanced grain growth behavior during superplastic deformation is analyzed on the basis of grain boundary diffusion mechanism. On the grain boundary where both static and dynamic potential differences exist, matter diffusing along the boundary is assumed to deposit on the grain surface locating opposite to the direction of grain boundary migration and to contribute to the dynamic grain growth. The amount of the diffusive matter is calculated for the deformation of a spherical grain and is converted to the increment in the mean boundary migration velocity. The obtained relationship between the strain rate and the dynamic grain growth rate is independent of the mechanism of superplastic deformation. The dynamic grain growth behavior predicted from the present model is consistent with the experimental results of ZrO2-dispersed Al2O3.
dynamic grain growth, strain, grain boundary, grain size, diffusion, superplastic deformation