Retaining meta-stable fcc-Cr phase by restraining nucleation of equilibrium bcc-Cr phase in CuCrZrTi alloys during ageing

Cr-rich precipitates with a bcc crystal structure are an equilibrium phase in high-strength Cu-Cr alloys. Metastable fcc Cr-rich precipitates that are coherent with a fcc Cu matrix were retained in a Cu-Cr-Zr-Ti alloy during ageing. Atom-probe tomography analysis revealed that Cr atoms exist in the core of the Cr-rich precipitates, whereas Zr atoms segregate on the periphery. Fcc Cr-rich precipitates are prone to form because of the low nucleation barrier. A rapid diffusion of Ti atoms in the matrix stimulates the fcc Cr-rich nuclei growth. Resulting solute-lean zones hinder further nucleation of equilibrium bcc Cr-rich precipitates.