Analysis of Stored Energy in Cold-Rolled Copper Using Bulk and Microstructure-Based Techniques

Abstract

Measurements of stored energy have been obtained for samples of copper cold-rolled to von Mises strains between 0.42 and 5.21 using both differential scanning calorimetry (DSC), and based on measurements of microstructural parameters in the transmission electron microscope (TEM). In both cases, a linear increase in stored energy with strain is found. The ratio between the two measured values varies, however, over a significant range, indicating that some caution is needed in determining the relative difference in energy associated with deformation microstructure heterogeneities in a given sample. Comparison of the stored energy with the flow stress suggests that the TEM-based measurements reflect the dislocation density content responsible for the flow stress, but that the DSC technique additionally measures other contributions to the stored energy, such as the presence of balanced internal stresses.