Evolution and strengthening mechanism of metastable precipitates in Cu-2.0 wt% Be alloy

The γ" phase and the γ′ phase are metastable precipitates in Cu-2.0 wt%Be alloy, which play a key role in strengthening the alloy. This paper mainly discusses the formation process, microstructure and strengthening mechanism of these two precipitates. The structure, quantity and size of precipitates in the alloy treated at different aging temperatures were analyzed by transmission electron microscopy (TEM). The strengthening mechanism of the γ" phase and the γ′ phase was analyzed by theoretical calculation. The results show that with the increase of aging temperature, the size of γ" phase changes slightly, but the density decreases significantly, while the size and density of γ′ phase increase with the increase of aging temperature. High resolution transmission electron microscopy (HRTEM) analysis shows that the γ" phase is semi coherent with the matrix, so it will be cut off by dislocations. The atoms in the γ′ phase are arranged perfectly, they can't shear with dislocations, so they can be strengthened by the Orowan dislocation bypass mechanism. The strength mechanism of γ" phase is location shear mechanism and the strengthening mechanism of γ′ phase is Orowan bypass mechanism.