Concept of 'Axial-Symmetry Constraint' and Its Significance in Recrystallization.

摘要

Grain growth and grain impingement that occur during recrystallization are simulated reasonably well with a simplified computer model that is based on a regular geometric grain growing in an impingement cell. The model also generates effective kinetic simulations, but only when the axial symmetry of the grain is constrained to the axial symmetry of the impingement cell. This condition is defined as the ''axial-symmetry constraint.'' When the simulated grain geometry deviates from the axial-symmetry constraint, the simulated kinetic behavior shows corresponding deviation from predicted kinetic behavior. These results imply that the geometry by which recrystallized grains fill space is more important than the actual shape if recrystallized grains. The physical significance of this concept is that the geometric shape of the interface between recrystallized and unrecrystallized material is dictated by the local deformation geometry. Once grain impingement commences and clusters of contiguous recrystallized grains form, the model interface corresponds to the interface formed by the grain clusters. The simulations reveal that interfacial areas dictated by deformation geometry are significantly greater for rolling than for extrusion, and this result correlates with experimental observations that recrystallization is more rapid in rolled materials than in extruded materials for the same initial grain size and similar reductions. Since recrystallization is an interface-controlled reaction, the axial-symmetry constraint appears to be an important concept that could contribute to improved kinetic models. 17 refs., 5 figs.