Nanocrystalline Zn was prepared by cryomilling(mechanical attribution at liquid nitrogen temperature). Differential scanning calorimetry(DSC), x-ray diffraction, and transmission electron microscopy were used to study the structural changes and grain size distribution with milling time and subsequent annealing. Maxima in both stored enthalpy(for the low-temperature DSC peak)and lattice strain on the Zn basal planes were observed at the same milling time. Dislocation density on the basal planes is proposed as a major source for lattice strain and the measured stored enthalpy. The released enthalpy that might be due to grain growth is very small.
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