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We performed a three-dimensional (3D) analysis of ferrite grains recrystallized in low-carbon steel during annealing. Cold-rolled specimens were heated to 723 K and held for various periods. The 3D morphology of ferrite grains recrystallized during the annealing process was investigated. The progress of recovery in low-carbon steel was more inhibited than that in pure iron. However, ferrite recrystallization in low-carbon steel was more rapid than that in pure iron. The Avrami exponent was inconsistent with the 3D morphology of the recrystallized ferrite grains in pure iron but consistent with that of the grains in low-carbon steel. Thus, the Avrami exponent depends on the recovery and recrystallization behaviors. Furthermore, the recrystallized ferrite grain growth was virtually 2D. Three types of recrystallized ferrite grains were observed: recrystallized ferrite grains elongated along the transverse or rolling direction; plate-shaped recrystallized ferrite grains grown in the transverse and rolling directions; fine and equiaxed recrystallized ferrite grains. These results suggest that the recrystallized ferrite grains did not grow in the normal direction. Thus, we concluded that the 3D morphology of recrystallized ferrite grains depends on the kinetics of recrystallization and the initial microstructure before recrystallization.

The acceleration of gravity is often an important factor influencing a processing procedure, in addition to thermodynamic parameters such as temperature and pressure, especially when a fluid phase is involved. Accordingly, the control of acceleration is important to obtain high quality materials, and to understand the heat and mass transport phenomena during the process. In recent years, materials processing experiments have been performed not only in microgravity but also in hypergravity environments. Utilization of a centrifuge is used to generate hypergravity acceleration on earth. Most centrifugal crystal growth experiments were employed to study the relationship between acceleration and 1) composition and defect distributions in the resulting crystal,e. g,1,22) sedimentation during growth,3 3) morphological instability of the solid/liquid (S/L) interface,4,5 4) growth striations,6,7 5) temperature oscillations in the liquid phase, 8,9 and 6) heat transmission.10