抄録
Researches on aging during one hundred years of Duralumin were projected by Prof. Masaji GOTO and cooperators in Metallugical division of the Aeronautical Research Institute, Tokyo Imperial University.
Test pieces were prepared in 1927 and has been preserved by Prof. Shiro ISida and subse-quently by Prof. Hiroshi ASADA.
Preparation of the test pieces was as follows:
Aluminium wire bar made in Aluminium Co. of England, magnesium ingot, electrolytic copper and Cu-Mn mother alloy were melted in graphite crucible. Standard composition: Grop I-Cu4%, Mg2Si0.75%, Mn0.5%, Al the balance. Group II-Cu4%, Mg2Si0.75%, Si1%, Al the balance. Maximum temperature for melting was 750°C. Ingot was 30×100×120mm of size and was hot-rolled at 450°C to 6mm of thickness and annealed at 350°C for 30 minuts and cold-rolled to 5mm of thickness. Tensile test pieces were quenched in water from 520°C after keeping in salt bath for two hours.
The test pieces had been preserved in a storage room of basement for some periods until 1934 without any protection, since when they have been preserved in a steel-locker in ordinary room.
It seems that, after 28 years, tensile strength has become more or less lower and elongation more or less higher.
