Influence of grain size and quenching rate on the age-hardening behavior of Cu-2%Be alloy

The influence of grain size and quenching-rate on the age-hardening behavior of a Cu-2%Be alloy was investigated at 593 K after water-quenching and air-cooling from 1093 K. In the initial stage of age-hardening of the water-quenched specimen, the grain size dependence of hardness was observed; namely, the smaller the grain size, the lower the hardness. Moreover, the hardness in the regions adjacent to grain boundaries in a large grain was lower than that at the central region of a grain. These phenomena can be explained by the mechanism that the vacancies existing in the regions adjacent to grain boundaries at the solution-treatment temperature move to grain boundaries to disappear during water-quenching, resulting in the retarded G.P. zone formation in these regions in the subsequent aging. In the case of the low quenching rate(air-cooling), the formation of G.P. zones is suppressed in the whole regions of grains and thus the grain size dependence of hardness was scarcely observed.