The New Grain Formation During Warm and Hot Deformation of Copper

Initial stage of dynamic recrystallization (DRX) under warm and hot deformation was investigated in polycrystalline copper. At the onset of DRX at intermediate deformation temperatures (i.e., high values of Zener–Hollomon parameter $Z$⁠) large orientation gradients are developed near grain boundaries, and conversely smaller gradients at high temperatures (i.e., low $Z$ values). The frequency of thermally activated grain boundary motion coupled with various levels of local orientation gradients lead to the operation of different mechanisms of DRX nucleation. At warm deformation equiaxed grains with moderate- to high-angle boundaries are evolved at near the pre-existed boundary as a result of increasing density of geometrically necessary boundaries and progressive rotation of subgrains with little accompanying boundary migration, while at hot deformation grain boundary bulging accompanied with twinning takes place.