Thermomechanical processing

The softening mechanisms associated with deformation processing are described in detail. These include: dynamic recovery (DRV), static recrystallization (SRX), dynamic recrystallization (DRX), and metadynamic dynamic recrystallization (MDRX) or postdynamic recrystallization. The precipitation of second phases, such as the carbonitrides in microalloyed steels, is considered, as is the interaction between precipitation and recrystallization. The modeling of the softening processes is outlined together with that of the rolling load and grain size. A distinction is drawn between rough rolling, which involves full recrystallization between passes, and finish rolling, in which case no recrystallization takes place, leading to “pancaking” of the microstructure. The effect of such pancaking on phase transformation and grain refinement in complex materials such as steels is described, together with that of cooling rate through the transformation. Some attention is also paid to intercritical and warm rolling as well as to the production of ultrafine grained materials. Next, the effect of thermomechanical processing on mechanical properties is considered. Texture formation during rolling is characterized for both face-centered cubic (fcc) and body-centered cubic (bcc) crystal structures and recent advances in thermomechanical processing, both theory and practice, are depicted briefly. Finally, the processing of nonferrous metals, such as aluminum and titanium alloys, is considered.