MECHANISM OF GRAIN REFINEMENT DURING EQUAL-CHANNEL ANGULAR PRESSING AT INTERMEDIATE TEMPERATURE IN AN Al-Mg-Sc ALLOY

摘要

The mechanism of grain refinement of an Al-5.4Mg-0.4Mn-0.2Sc-0.09Zr alloy subjected to equal-channel angular pressing (ECAP) with a back pressure (BP) for up to 12 passes via route Be at 573K (300°C) was studied. New grains form through a specific mechanism of continuous dynamic recrystallization (CDRX). At the first pass of ECAP, formed geometrically necessary boundaries play a vital role in initiation of recrystallization process due to formation of planar lamellar structure. The second pass led to transformation of this planar to 3D net of sub-boundaries which are changes into high-angle boundaries at further deformation. The formation of primary MSBs is associated with the appearance of texture α-fiber, and the appearance of a new type of shear texture, which is an axial {112} texture of orientation around the transverse direction accompanies the formation of ultra-fine grains.