Use of TEM Kikuchi Bands for Microstructure and Thermal Stability Study of ECA Pressed AA1200 via Routes A, C, Bc

摘要

The evolution of the microstructure during ECAP depends upon the shearing deformation paths introduced into the material. Some authors, using selected-area electron diffraction, reported an effectiveness of cell (low-angle boundaries) evolution toward high-angle boundaries on the order Bc > C > A. This study focused on the cell and grain boundary evolution of an AA1200 during ECAP, up to a true strain of E=8.64, in routes A, C, and Bc. TEM Kikuchi bands were used for the quantitative evaluation of boundary misorientation. A different hierarchy of cell evolution to grains was found, and this was as C > Bc > A; while in terms of reducing grain size, the route efficiency remained as Bc ≥ C > A. Thermal stability of the severely deformed alloy was studied by annealing the alloy at 0.5, 0.6, 0.7 T_M for 2 hrs. It appeared that, even if route Bc is the one involving a faster microstructure grain refining, route C is likely to be the most stable upon reheating.