Grain Refinement Mechanism of 5A06 Aluminum Alloy Sheets during Cold Rotary Forging

This paper studies the grain refinement mechanisms of 5A06 aluminum alloy sheets in cold rotary forging (CRF). The results show that the grains are clearly refined from 25.1 µm to 11.8 µm during the CRF process. The grain refinement mechanism can be divided into two modes: (1) The grains with a small Schmid factor (SF) are activated by multi-slip systems, and dense dislocations are segregated along the boundaries of interior regions with different slip systems, which results in a rapidly increasing strain localization along these boundaries. Since the strain localization restrains the coordinate slip deformation between different interior regions, the grains are directly separated into several finer grains. (2) The grains with a large SF are primarily activated by a single slip system, and the dislocation migrates smoothly along most microband boundaries. Then, a more severe lattice rotation causes a transformation to a hard orientation and multi-slip system activation, which contributes to an increase in the rapid misorientation across microband boundaries and thus promotes significant SF grain refinement.