Microstructure evolution in deformed copper

The effects of strain and temperature on the microstructure and the detailed structure of dislocation walls in compressed pure polycrystalline copper were systematically studied. The microstructure observed consisted of dislocation cells and second generation microbands (MB2) and is presented in a microtructural map. The detailed structure of the cell's boundaries evolves with increasing strain and/or temperature from tangled dislocations into arrays of parallel dislocations. Interplay between strain and temperature controls the microstructure and the detailed structure of the dislocation boundaries. Above 0.5 T_m only MB2 are observed; a different type of MB2 is also observed, one order of magnitude wider than the one observed at the lower temperature. With increasing strain and temperature the MB2 density increases. It seems that dislocation cells and MB2 are competitive dislocation patterns and at elevated temperatures the MB2 is the preferred dislocation pattern.