On the early stage in the aging of Al-Cu alloy

Abstract

In this paper, the phenomena in early stages of aging are studied by measuring the damping capacity, hardness, decrement of the oscillation of Harbert pendulum and specific volume on Al-Cu alloys which contains 3.1∼6.2% Cu in aluminium basis.
As the result, the damping capacity fluctuates widely in early stages like in the case of 17S or 2S which was previously reported on. The fluctuation is seen in Al-3.116% Cu alloy most widely, while it is less in 6.200% Cu alloy and 4.240% Cu alloy. As to the hardness curve, it seems that as the copper content increases, the aging time up to the saturated hardness number gets shortened slightly and the fluctuation of the hardness decrease but there is the fluctuation, which seems to be beyond the dispersion of the mesuring value of hardness during the period up to the saturated hardness in aging. These results correspond with the changes found out by measuring the decrement of the Harbert pendulum or by analysing the specific volume, and consistent with the previous consideration from the viewpoint of G. P. zone that the internal changes in early stages of aging up to intermediate precipitation are very complex, the local changes of the solubility are grow one after another, and the properties change fluctuately like the “wavelike form” and approach the saturated conditions.