EFFECT OF LUBRICATION ON THE EVOLUTION OF MICROSTRUCTURE AND TEXTURE DURING ROLLING AND RECRYSTALLIZATION OF COPPER

Two polycrystalline copper specimens were deformed by cold rolling wit h and without lubrication so as to achieve different deformed microstr uctures. The effect of the different rolling procedures on the evoluti on of microstructure and texture during rolling and recrystallization was studied by microstructural observations and X-ray texture analysis . In addition, local orientations in the as-deformed state were determ ined by selected area diffraction (SAD) in a transmission electron mic roscope (TEM) and, after recrystallization, by electron backscattering diffraction (EBSD) in a Scanning electron microscope (SEM). Whereas t he rolling textures of the two differently rolled sheets were surprisi ngly similar, the microstructures strongly differed in so far as the s ample rolled without lubrication contained a much larger amount of she ar bands. The present results suggest that the shear component epsilon (13) caused by friction during dry rolling can effectively be dissipat ed by shear band formation, resulting in a rather homogeneous overall rolling texture. With regard to nucleation of recrystallization, shear bands are known to cut the typical nucleation sites of the cube-orien tation, the main recrystallization texture component of rolled copper, but they are also able to act as new nucleation sites. Furthermore, g rowth of the new recrystallized grains is hindered by the shear bands because of microstructural and orientation discontinuities at the matr ix-shear band interfaces. This led to a strong retardation of the recr ystallization process and gave rise to a very fine grained microstruct ure and a weak recrystallization texture in the specimen cold rolled w ithout lubrication. (C) 1998 Elsevier Science S.A. All rights reserved .