A General Treatment of the Distribution of Vacancies to Solute Atoms in a Ternary Solid Solution and its Application to Low Temperature Aging in Al–Cu–Sn Alloys

Abstract

A general treatment to calculate the concentration of vacancy-solute atom pairs in a ternary dilute solid solution is presented. This treatment is applicable to a wide range of vacancy concentration relative to the concentration of one kind of solute atoms. The treatment is applied to explain the effect of tin addition on the rates of low temperature aging in Al-Cu alloys. The difference in the activation energy for aging between Al-Cu alloys and an Al-Cu-Sn alloy is analyzed to find the binding energy of a vacancy-tin atom pair to be about 0.3eV larger than that of a vacancy-copper atom pair. The experimental result that the retardation of aging due to tin addition is appreciable only for tin concentrations larger than the vacancy concentration is also explained satisfactorily.

The effects of alloying with Cu and Mn and thermal treatments on the mechanical instability of Zn-0.05Mg alloy

“…It is speculated that the interaction between Mg and Mn/Cu atoms in the solid solution slows down the diffusion of solute atoms and prevents the formation of Mg-rich precipitates, which suppresses the natural aging of alloy. A similar mechanism was found by other researchers in Al-Cu when alloyed with tin [27,28]. The addition of Sn to Al-Cu alloy slows the natural aging as a result of stronger Sn-vacancy bonding energy and thereby, reducing the amount of vacancies.…”

Natural Aging in Al‐Mg‐Si Alloys – A Process of Unexpected Complexity

“…[46] The increase in hardness during NA is caused by the growth of a high density of clusters that have a higher shearing resistance to dislocations than the supersaturated matrix. The early fast process gradually changes to the later stage slow process over the interim period (50-800 min) which appears to be a combination of the fast and slow processes.…”