Observation and modeling of dynamic recrystallization in high-strain, high-strain rate deformation of metals

The microstructural evolution inside shear bands was investigated experimen tally and analytically. A fine recrystallized structure (grains with 0.05-0 .3 mu m) is observed in Ti, Cu, 304 stainless steel, Al-Li, and Ta, and it is becoming clear that a recrystallization mechanism is operating. The fast deformation and short cooling times inhibit grain-boundary migration; it i s shown that the time is not sufficient for migrational recrystallization. A rotational mechanism is proposed and presented in terms of dislocation en ergetics. This mechanism necessitates the stages of high dislocation genera tion and their organization into elongated cells. Upon continued deformatio n. the cells become sub-grains with significant misorientations. These elon gated sub-grains break up into equiaxed grains with size of approximately 0 .05-0.3 mu m. It is shown that grain-boundary reorientation can operate wit hin the time of the deformation process.