Comparison of the thermal stability between electro-deposited and cold-rolled nanocrystalline copper samples

The objective of this work is to investigate the microstrain effect on grai n growth and strain release processes in nanocrystalline (nc) samples. Two kinds of nc Cu samples were studied by using differential scanning calorime try (DSC), X-ray diffraction (XRD) and transmission electron microscopy (TE M): an electro-deposited nc Cu sample with an average grain size of about 3 0 nm and one after cold-rolling in which the average grain size remain unch anged but the microstrain is substantially elevated. Measurement results in dicated for the electro-deposited nc Cu, grain growth occurs at about 70 de grees C, which was prior to the major strain release process (onset at 150 degrees C). While for the as-rolled nc Cu, the grain growth onset temperatu re increases up to about 150 degrees C and that of the strain release proce ss drops to about 115 degrees C. These results showed an evident correlatio n between the grain size stability and the microstrain in the nc materials. (C) 2000 Elsevier Science S.A. All rights reserved.