3D-AP and positron annihilation study of precipitation behavior in Cu–Cr–Zr alloy

Precipitation behavior in a Cu–0.78%Cr–0.13%Zr alloy during aging and reaging has been studied by laser-assisted local electrode three-dimensional atom probe (Laser-LEAP) and positron annihilation spectroscopy (PAS). After the prime aging at 460 °C, Cr clusters enriched with Zr were observed. Further reaging at 600 °C caused the clusters to grow to almost spherical (1 h) and thick platelets (4 h) Cr precipitates. Zr and impurities of Si and Fe were concentrated around the Cr precipitates, resulting in almost pure Cr cores sandwiched with interface regions enriched with Zr, Si and Fe. Probably the strain induced by the incoherency between BCC Cr precipitates with the matrix FCC Cu is relaxed by the enrichment of Zr, Si and Fe. Positron lifetime and coincidence Doppler broadening experiments suggest that vacancy-like defects form and associate with Cr atoms around the interfaces between the precipitates and the matrix.