Medium-strength 6061 aluminum alloy is a suitable material for general-purpose structural use because of a good corrosion resistance and a good toughness. The effect of hot forging conditions on the microstructure in a 6061 aluminum alloy has been closely investigated, and the mechanism for the microstructure formation has been discussed. Specimens of 6061 aluminum alloy ingots were hot-forged at various temperatures and strain rates, and then T6-tempered. Microstructures of as-forged samples as well as T6-tempered ones were characterized mainly with EBSD and TEM. Non-recrystallized structures were formed by hot forging at all the Zener Hollomon (
Z) parameters from 1.1×10
6 s
-1 to 1.4×10
12 s
-1, which consisted of grains surrounded by high and low angle grain boundaries. The microstructure became refined with increasing
Z. This refinement was attributable to grain subdivision mechanism that occurred during hot forging. Because of finer microstructure prior of solution treatment and non-occurrence of recrystallization, the microstructure in samples of middle
Z was finer than that of low
Z. In samples of the low
Z and the middle
Z conditions, these microstructures were thermally stable and did not change, even after high temperature solution heat treatment. In contrast, in samples of the high
Z condition, a small number of nuclei were considered to form in the deformation microstructure because of high density of dislocations, resulting in coarse recrystallized microstructure.
View full abstract