COMPARISON OF SUBSTRUCTURES IN HIGH-TEMPERATURE DEFORMED ALUMINUM-ALLOYS BY POLARIZED OPTICAL, SCANNING AND TRANSMISSION ELECTRON-MICROSCOPES

Microstructural investigation on Al, Al-11Zn and Al-5Mg alloys deforme d at high temperatures in torsion were conducted using POM, SEM with E BSI and EBSP as well as TEM. The results indicate that POM can be used to reveal subgrain structure for Al and Al-11Zn, but mainly grain str ucture for AI-5Mg. For Al-5Mg the real grain size with misorientation theta > 10 degrees C, which is determined by EBSP, is smaller than tha t measured by POM. This suggests that POM may not reveal all large ang le grain boundaries for strongly solution hardened alloys. In the orde r POM, SEM and TEM, they can be applied to reveal more information abo ut subgrain structures for Al alloys. Inadequate observation by POM of subgrain structures for Al-5Mg may be explained by smaller subgrain s ize and higher internal dislocation density than those for Al, which a rises from the solution hardening by Mg atoms.