IN-SITU SEM OBSERVATION OF MICROSTRUCTURAL EVOLUTION OF HIGH-PURITY ALUMINUM DEFORMED AT ELEVATED-TEMPERATURES

The subgrain evolution in high purity aluminum (4N) has been observed in-situ during high temperature deformation, by means of the crystallo graphic contrast obtained from the backscattered electron signal of th e scanning electron microscope (crystallographic contrast technique). It was observed that the substructure on the surface of the deformed s ample represents the substructure developed inside the material. Evide nce of increasing misorientation between adjacent subgrains and grain boundary migration with increasing strain is reported. This subgrain s tructure remains unchanged at room temperature when the applied stress is maintained during cooling. The crystallographic contrast technique demonstrates to be appropriate to measure subgrain size. Subgrain siz e values similar to those obtained by transmission electron microscopy are reported when the method of images superposition is incorporated to this technique.