In situ synchrotron radiation topography of NaCI during high temperature creep

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Abstract
High temperature plastic deformation is associated with large changes in the microstructure of single crystals. To observe this microstructure during the creep test, we have performed X-ray reflection topography, taking advantage of the high intensity of the synchrotron radiation. A special creep machine was designed which permits in situ observation. Creep tests and microstructural observations were performed on NaCl single crystals compressed along at about 600°C. As soon as the deformation started, subgrains appeared within the crystal, independent of the initial microstructure. Migration of the subboundaries during transient creep is followed by stabilization during steady state creep where a well developed subgrain structure keeps constant while new appearing subboundaries migrate. Misorientation between sub-grains increases progressively although more slowly in the steady state creep. A correlation between the microstructure evolution and the changes in the creep curves has been attempted.