Twins, annealing deformation

Fig. 14. Twins produced by plastic deformation and broadened by annealing at 650°C in an imperfect single crystal of a - U grown by progressive phase-change from j3 to a. The bands with different shades correspond to the recovery of the subgrains of the initial crystal. Electroetching reveals small disorientations between the subgrains X150. (D. Calais, P. Lacombe and Mme Simenel, Rev, met., 56, 261 (1959)).

Fig. 2-23 Twinned grains (a) and (b) FCC annealing twins (c) HCP deformation twin.

In this section, the formation of deformation and annealing twins were discussed with the resulting stress-strain relation characterized by serrated curves. As indicated here, there is no basic difference in twin formation between ceramics and metals. 

Sphalerite deformed at temperatures up to 500 °C and strain rates between 10 and 10 s produced no twins in Fe-rich sphalerite [411,412] but abundant twinning in purer specimens [412], together with slip under all test conditions. The annealing of naturally and experimentally deformed sphalerites suggests that static recovery is possible above 300 °C and proceeds rapidly above 500 °C [412]. Recrystallization produces new grains with numerous growth twins. 

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