Nucleation and growth of nanoscale precipitates and the effect on properties during secondary isothermal aging in thin-band of Cu–0.8Cr–0.1Zr alloy

Abstract

The precipitation behavior during secondary isothermal aging of Cu–0.8Cr–0.1Zr alloy, especially the nucleation and growth of nanoscale body-centered cubic (bcc) Cr and orthogonal Cu4Zr precipitates, were clarified through high-resolution crystal structure and atomic-scale composition analysis. Results demonstrated that the crystal-nucleus of face-centered cubic (fcc) Cr and fcc Zr would be preferentially precipitated in a coherent orientation relationship (OR) with fcc Cu-based matrix. As they grew up, fcc Cr gradually developed into stable bcc structure, and the OR with matrix changed from N-W to incoherent. While fcc Zr would change lattice constant by atomic diffusion and segregation to evolve into stable Cu4Zr with orthogonal structure, during which they were precipitated on the Cu–Cr–Zr solid solution through a process of discharging surrounding Cr atoms. Abundant dispersed nanoscale precipitates that induced by the secondary aging contributed to produce well-matched comprehensive properties (σb=669 MPa, I = 84.3 %IACS).