Al-1.3%Mg2Si合金の二段時効について
1969 年 19 巻 2 号 p. 41-46
詳細
1969 年 19 巻 2 号 p. 41-46
The effect of pre-ageing on artificial age-hardening of an Al-1.32%Mg2Si alloy at 170°C was investigated. Hardness was measured and it was found that there was some correlation between the hardness and microstructure revealed by transmission electron microscopy. The following results were obtained.
(1) When the pre-ageing was made at below the room temperature, the maximum hardness after ageing at 170°C was about 10% lower than that of no pre-ageing. On the contrary, when the pre-ageing was made at above 50°C, the maximum hardness after ageing was about 10% higher than that of no pre-ageing. However, in the latter case, the maximum hardness was lower when the pre-ageing was made for a very short time.
(2) The critical temperature for pre-ageing, at which the two-stepped ageing effect changed from positive to negative, was about 36°C.
(3) The observation of the structure by electron microscopy showed that coarse acicular precipitates were disperssed after the pre-treatment at 0°C for 7 days; while, fine acicular precipitates were very homogeneously distributed after the pretreatment at 100°C for 24 hrs.
(4) As the results of hardness reversion experiments, it was suggested that the thermal stability of G. P. zones formed by the pre-treatment was higher in the aging of at 100°C for 24 hrs. than that of at 0°C for 7 days.
Most of the above results of experiments can be interpreted by Pashley's kinetic model.
