Recrystallization of partially transformed lithium single crystals

When a transformed lithium single crystal is heated from the low-temperature phase, at 180 K a deteriorated b.c.c. single crystal is again obtained. When further heating, in the range of 200 to 230 K in neutron scattering investigations a decomposition of the single crystal into a polycrystal was observed. Analysis of this process by differential sampling calorimetry showed the presence of an exothermal annealing peak in this temperature range which follows the endothermal peak from the reverse transformation. The temperature range where the phenomenon occurs is ∼0.5 of the melting temperature. This fact as well as the experimentally determined activation energy strongly indicate that primary recrystallization takes place. The increased dislocation density of the re-transformed crystal enables the nucleation of large-angle grain boundaries though the sample was not mechanically deformed. (orig.)