GRAIN BOUNDARY AND PRECIPITATION EFFECTS IN DIFFERENT AlMn ALLOYS

Abstract
Internal friction and dynamic elastic modulus investigations completed by optical microscopy and microhardness measurements were made on cold drawn and recrystallized AlMn alloys with 0.03 - 1.1 wt%Mn content. Primary and secondary recrystallization caused pseudopeaks on the spectra of the as drawn samples. Primary recrystalization was indicated by a sudden decrease in microhardness too and a well detectable grain growth was obtained due to secondary recrystallization. Both recrystallization temperatures increase significantly with the Mn content. The strength of the grain boundary relaxation decreases rapidly with the Mn concentration for the small and large grained samples as well. For higher Mn contents the peak shifted to higher temperatures. Investigating the effect of different precipitation heat treatments we found that the temperature of the occuring relaxation peak was lower for the less stable precipitates formed at lower temperatures.