X線に依る超ヂュラルミン時効硬化の研究(第1報)

Abstract

The ageing of super-duralumin (RF1 Cu 4.01%. Mg 1.77% and RF 2 Cu 4.09% Mg 1.12%) and Al-Cu alloy (Cu 2% and 4%) was investigated by X-ray back reflection focussing method using Cu Ka radiation. The quenched specimen was fixed on an X-ray camera and incident X-ray beam was adjusted so as to illuminate the same part of the specimen always from the same direction. Photographs were taken immediately after, quenching, 15min., 30min., 1 hr., etc. and obtained following results. Some of the spots reflected from (511) planes of super-duralumin change their shapes by internal strain or bending of the crystal grains during ageing and this continues for several hours. At first, the change in the position of the spot is rather at random but finally it displaces to the side of larger-lattice constant. The mean dilatation of the lattice after 20 hrs. was 0.0121% and 0.0274% respectively, for RF1 and RF2, while the lattice constants immediately after quenching were 4.036 and 4.035 A. U. Above result confirms that of Nishinmra(1) who found that the natural ageing of super-duralumin is mainly concerned to the formation of ternary compound S or CuAl2. Regarding dilatations of the lattice the present author already observed in the case of duralumin(2). According to Nishimura's ternary diagram the formation of CuAl2 will also take place in RF2, and therefore the dilatation of the lattice of this alloy is larger than the other. The change in the shape of the spot and the displacement of its position is not so remarkable in Al-Cu alloy, but in some alloys having 4% Cu, bending of the atomic plane during ageing was very noticeable; the tendency of lattice dilatation was also observed.