Namio Kawashima1 and Yuzo Nakamura1
1Toyo Aluminium K.K.,
This paper deals with the abnormal hardening phenomena on the annealing curves of pure aluminium (99.5 ∼ 99.998 %) which have not yet been brought clearly to light. An abnormal hardening at lower temperature was clearly observed in the aluminium of 99.92 % purity which had undergone a lighter reduction less than 50 %, but it could not be recognized in the case of such a heavier reduction as 90 %. And the second abnormal hardening or incubation period was observed in all pure aluminiums. By X-ray analysis, it was ascertained that the beginning temperature of recrystallization exists in the incubation period or in the neighbourhood of second abnormal hardening.
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