Nano-Sized Precipitates in a Cast Cu–Cr–Zr Alloy and Their Evolution during Subsequent Heat Treatment

Abstract

Nano-sized precipitates in centrifugally cast Cu–0.43Cr–0.22Zr alloy and their evolution during subsequent solid-solution treatment and aging were investigated by TEM and HRTEM. They are particles of Cr and Cu–Zr phase, such as Cu₅₁Zr_14. Many nano-sized precipitates are found in the cast alloy; they will get smaller or disappear during solid-solution treatment and the dissolved atoms are inhomogeneously distributed in the copper matrix and form aggregations up to generation of very tiny clusters after solution quenching. Furthermore, aging treatment will create many new nano-sized precipitates, and causes the inherited precipitates being recovered and the clusters being grown, resulting in the formation of more and finer precipitates in the aged alloy in comparison with the case of the as-cast alloy. Therefore, it can be inferred that the more the tiny precipitates formed in the as-cast alloy, the more the precipitates in the aged alloy. The treatment combining solid-solution one and aging is beneficial to the formation of more and finer precipitates in a Cu–Cr–Zr alloy.