Study of thermal stability of ultrafine-grained copper by means of electron back scattering diffraction

Abstract

Thermal stability of ultrafine-grained (UFG) structure of 99.9% pure copper produced by eight equal channel angular pressing (ECAP) passes was studied. The annealing experiments were conducted at 180°C in a tube furnace under argon as a covering gas. The dwell times were in the range of 10 min to 120 min. The electron backscattering diffraction (EBSD) analyses were performed before and after annealing at exactly the same area in order to quantify the degree of decomposition of the UFG structure. Definition of grain boundaries was based on the !Disorientation angle of 1°. More advanced analysis of the EBSD results based on a kernel average !Disorientation (KAM) parameter was performed. Inverse pole figure maps with included grain networks did not reveal any substantial changes of UFG microstructure due to annealing. Some shift in the KAM modus in comparison with the initial state was observed but its magnitude was found negligible. Also changes in texture were found to be minor. On the other hand the microhardness increases with increasing time of annealing. © 2010 The Japan Institute of Metals.