A Method of Measuring Stored Energy Macroscopically Using Statistically Stored Dislocations in Commercial Purity Aluminum

Stored energy from plastic deformation in rolled aluminum has been quantified with both macroscopic and microscopic methods. Differential scanning calorimetry (DSC) and Microhardness tests were used to determine a value for stored energy based on energy released during recrystallization and resistance to plastic flow from the accumulated dislocation content, respectively. For a value of stored energy based only on geometrically necessary dislocations, orientation imaging microscopy (OIM) within a scanning electron microscope (SEM) was used and supported by transmission electron microscopy (TEM) observation of subgrain cell structure. A value for the average misorientation angle that could be associated with the TEM was obtained from the OIM data. The values of stored energy derived from the various analyses were found to be similar with slight overestimation from the OIM technique. Thus, the difference between the macroscopic and microscopic methods represented the statistically stored dislocations.