Al-Zn合金の不連続析出に対する温度-時間-組成組織図

抄録

Recently Koyama et al. (Ref. 2) proposed a Temperature-Time-Composition diagram which was named the T-t-c system diagram. By using this diagram, the sequence of phase transformation and the development of the microstructure with progress of ageing can comprehensively be described. In this paper we experimentally determined the T-t-c system diagram for the start of cellular precipitation in the Al-Zn alloy system by means of optical and electron microscopic observations and hardness measurements. The results obtained are as follows:
(1) With increasing Zn content and with increasing ageing temperature, the cellular precipitation starts in a short time ageing.
(2) The cell growth rate decreases with ageing time. This decrease will be attributed to the influence of the continuous precipitation on the cell growth.
(3) The T-t-c system diagram can be regarded as the phase diagram with time scale. Therefore the phase decomposition will be understood more deeply and clearly by using this T-t-c system diagram.