Hisakiti Shimba and Sadakiti Kitazima
In the past investigations, it was explained that there was the softening process before recrystallization of strained aluminium, namely, recovery process.
These investigations were carried out by using polycrystalline aluminium,which had received very complex strain in cold-working owing to disorientation of grains and irregularity of atomic arrangement at grain boundaries. For these reasons, the observed hardness values for the same specimen were at random and one could not find small changes in recrystallization.
Therefore we used single crystals for this experiment. According to our experimental results, there were two steps in recovery process. One is the softening process,the other the hardening process. And the second hardening process occurs through rather severe cold working before recrystallization itself.
On the other hand, microscopic observations were made. Judging from this observations, obviously the first softening process was reduced to the disappearance of strain (dislocations), but there were no changes in the second hardening process. Furthermore,the polygonization was a successive phenomena from the beginning of annealing(recovery)till the recrystallization, and yet probably it was related to deformation bands formed by cold working.
We are now obtaining some interesting results by electron microscopic investigation upon the second hardening process.
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