Al-Ag, Al-Ag-Zn合金の初期時効

抄録

Aging behaviour of Al-Ag binary alloys containing less than 0.11 at%Ag and Al-Ag-Zn ternary alloys containing a small amount of zinc were studied by the measurement of electrical resistivity.
The results may be summarized as follows:
(1) After isothermal aging below a certain temperature, the electrical resistivity of each Al-Ag binary and Al-Ag-Zn ternary alloys increases initially, reaches a maximum value and then decreases corresponding to the formation and growth of G.P. zones. But when aged isothermally above a certain temperature, the electrical resistivity shows a slight initial increase and then decreases very slowly, with no distinct maximum in the isothermal aging curves. In this case, G.P. zones seem not to be formed and the small increase of electrical resistivity is related to some behaviour of the supersaturated solute atoms. Therefore, these critical temperatures seems to be the highest temperature at which G.P. zones can be formed in Al-Ag binary and Al-Ag-Zn ternary alloys.
(2) The highest temperature at which G.P. zones can be formed in Al-Ag-Zn alloys containing a small amount of zinc is higher than that in the Al-Ag binary alloy containing the same amount silver. Namely, G.P. zones becomes stable at the initial stage when a small amount of zinc is added. This effect become remarkable when the concentration of zinc increases.