ON THE RECRYSTALLIZATION PHENOMENON OF THE HIGHEST PURITY ALUMINIUM (99.998%)

Abstract

Synopsis.
It has been said since 18 gears ago that the highest purity altminum such as 99.998% should be recrystallized eyen at room tcmperature. The authors read in a paper on this problem at the Tokyo meeting of the Japan instjtute of Metals held last spring. In this studies it was found that a self-annealing phenomenon locally took place with the aluminum of ovcr 99.996% purity during heavy rolling. Futhermore, it was ascertained by means of X-ray analysis that even the specimen of rolled condition not yet recrystallized began to recrystallize after 40 day's aging at room tempcrature. However, it was very difficult to find out a new recrystallized grain by ordinary microscopic examination.
So it is assumed the short line spots on the Debye arcs of Laue pattern, to be considered as the begining of recrystallization, should be taken as polygonization and not as ordinary nucleation.
Further, the authors investigated again the recrystallization phenomenon of the highest purity aluminum by means of X-ray analysis and microscopic examination to ascertain at what temperature the nucleation might take place. And the effect of aging on the recrystallization phenomenon of the highest parity aluminum was also looked into after 17 months aging. It was found out that the temperature of nucleation with the highest purity aluminum was respectively 100-110°C and l70-180°C at the reduction rate of 90% and 60%. And it was also ascertained that the highest purlty aluminum af less than 99.994% purity aluminum of 90% reduction was nucleated after 17 months' aging at room temperature, and that the aluminum of less than 99.994% purity did not show any recrystallization phenomenon after the same aging period.