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THE BELL SYSTEM TECHNICAL JOURNAL, OCTOBER 1951 



The metal used in all this work was 99.993% French aluminum rolled 

 into 0.005" sheet. 



Recovery of Cold Worked Aluminum 



Having briefly discussed the essential phenomena in interpreting electron 

 images of crystals, the application of the thin section method to self-recovery 

 in deformed aluminum can be demonstrated. This type of investigation is 

 based to a considerable extent upon comparison of images of the metal 



Fig. 6 — Extinction contours due to rumpling in an annealed high purity (99.993) 

 aluminum section. 



under various conditions of anneal and plastic deformation. The standard 

 state for comparison is a well annealed specimen in which the crystals are 

 reasonably perfect. The bending or rumpling produces the extinction con- 

 tour patterns quite unique to the annealed condition. The chief charac- 

 teristics of the contours for an annealed crystal are their general continuity 

 and extension over relatively large areas. Figure 6 illustrates a contour 

 pattern with an unusually high density of lines obtained from an aluminum 

 section annealed 30 min. at 335°C. The dark regions are those of electron 

 deficiency. 



At a grain boundary in an annealed section the contours end abruptly 



