In order to estimate the strain energies of pure Cu and pure Al, prepared by equal-channel angular processing and accumulative roll bonding, the dislocation densities remaining in the metals after each process were analyzed by using the Warren-Averbach method based upon the Williamson-Hall plot of a series of data obtained by conventional X-ray diffractometry. It was found that the measured dislocation density was higher, by several times, in pure Cu than in pure Al; regardless of whether equal-channel angular processing or accumulative roll bonding was used, resulting in a higher strain-energy being stored in pure Cu than in pure Al. Also, the dislocation density was found to be lower in the face-centred cubic phase in pure Cu than that in the lath martensite phase in high-Cr ferritic steels. Furthermore, it was observed that the amount of stored strain-energy in pure Al depended markedly upon its purity.

Assessment of Strain Energy by Measuring Dislocation Density in Copper and Aluminium Prepared by ECAP and ARB. Y.Murata, I.Nakaya, M.Morinaga: Materials Transactions, 2008, 49[1], 20-3