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Abstract
The grain structure of coarse-grained Cu of different degrees of purity was modified by plastic deformation by , 4 and 8 passes of equal channel angular pressing (ECAP) at an ambient temperature with and without back pressure. The effect of this modification on deformation resistance was tested in rate change tests in compression at elevated temperatures up to 473. Electron microscopy and compressive strength evolution with strain confirmed that static recrystallization leads to grain coarsening during heating to test temperatures of 423 for
and 473 for
and that discontinuous grain coarsening by dynamic recry- stallization sets in already at
. The influence of the grain structure on the deformation resistance is discussed in terms of a control loop considering generation and loss of free dislocations. The magnitude and rate dependence of the maximal deformation resistance of unrecrystallized ECAPed Cu were explained in terms of dynamic recovery at low- and high-angle boundaries as proposed previously. The interpretation sheds doubt on the common interpretation of rate change experiments in terms of thermally activated glide.
Acknowledgments
The authors gratefully acknowledge the funding of the German Research Council (DFG), which, within the framework of its Excellence Initiative, supports the Cluster of Excellence Engineering of Advanced Materials at the University of Erlangen-Nürnberg. The authors are also very grateful to Prof. R. Lapovok, Dr. A. Böhner and Dr. M. Hockauf for ECAP-processing of the materials and to Dr.-Ing. Philip Eisenlohr for valuable discussions and support in figure preparation.
Notes
Plotting on the ordinate facilitates comparison with the
-averages in subsequent figures.