Al-Cu-Mg合金の時効過程

抄録

The ageing process of a binary Al-Cu and ternary Al-Cu-Mg alloys was investigated by the resistometric method. The characteristics of the process in the ternary alloys are summarized as follows:
(1) In ternary alloys with Cu:Mg atomic ratio of 1:1, G.P.B. zones are formed with higher density but at lower rate of growth than G.P.(1) zones in a binary Al-Cu alloy. G.P.B. zones are thermally more stable than G.P.(1) zones.
(2) The activation energy of pre-precipitation in a binary Al-Cu and ternary Al-Cu-Mg alloys was determined to be 0.60±0.05 eV and 0.67±0.05 eV, respectively. Hence the formation of G.P. zones is thought to be controlled by the enhanced diffusion of solute atoms by the quenched-in vacancies in ternary alloys as well as in a binary alloy.
(3) On the specimens quenched from 520°C and aged at room temperature, dislocation loops of an average diameter of about 1000 Å were observed by electron microscopy and their density was 10¹⁴/cc. The growth of loops occurred for the first 6 hr when aged at 30°C but no further growth was observed. Concentration of quenched-in vacancies necessary for forming these loops were estimated to be 4×10⁻⁴.
(4) In ternary alloys the rate of zone growth increased with ageing time at room temperature, whereas it decreased monotonically in a binary Al-Cu alloy.