In the forging ring, the structure changes during the forging process. The first is the initial stage of deformation, forming a substructure with high density dislocations.
These dislocations can be homogeneously distributed or become subgrain boundaries of brittle substructures.
These substructure types can also be observed in cold deformation. When the softening process is not obvious, this stage of thermal deformation can be named as the hot work hardening stage.
This is followed by the second stage of the forging ring change, including the rising portion of the deformation curve but: >O.07-0.1.
At this time, the enhancement factor is lowered. Due to the enhancement of the softening process, a polygonal subgrain boundary is formed. There is a relatively high degree of free dislocation density in the subgrain boundary region. During the deformation process, the polygonal substructure gradually replaces the hot processed structure. The multilateral substructure itself is also changing.
First, the forging ringforms a subgrain boundary that divides the grains along a certain crystal plane. As the stress increases, the subgrain boundaries form along more crystal faces. Therefore, through the initial sub-grain, combined with the rounding of the subgrains due to boundary annexation, the process and multilateralization, repeated multilateralization process, the result is the formation of nearly equiaxed subgrains. This phase is completed with the formation of a fully multilateral substructure and equiaxed crystals under conditions where the deformation slightly exceeds the initial stage of the stabilization phase.
In the actual process of constant stress in the last deformation stage, the equiaxed polygonal substructure remains unchanged. The stability of the subgrain size is ensured by repeated multilateralization—a continuous process of formation and destruction of subgrain boundaries at equilibrium distances. Therefore, in the last two phases, dynamic multilateralization is the main process of structure formation.www.morayshaft.com