Effect of back pressure on the thermal stability of severely deformed copper

The effect of back pressure during equal channel angular pressing on thermal stability of Electrolytic Tough Pitch (ETP) copper was studied. The thermal behavior was assessed by means of microhardness measurements and microstructure characterization of the deformed samples at various stages of annealing. The assessment of the variation of the recrystallized fraction of the material with annealing was also carried out using a relatively new method based on internal misorientation measurements by EBSD technique. A higher stored energy and lower activation energy for recrystallization in the case of a back pressure of 100 MPa was obtained by means of DSC analysis. As a main outcome of this work, it was found that application of back pressure reduces thermal stability of the UFG microstructure. However, the effect is relatively small and does not negate the advantages of processing with back pressure in terms of the degree of grain refinement and strength enhancement.