Influence of trace silicon addition on the strengthening precipitates, mechanical properties and stress relaxation resistance of Cu-Cr alloy

First-principles calculations and experimental studies, including transmission electron microscopy (TEM), electrical conductivity measurements, and yield strength and stress relaxation resistance tests, were carried out to determine the influence mechanism of trace Si on the precipitates and stress relaxation resistance of a Cu-Cr alloy. TEM observation and aging precipitation kinetic analysis showed that the addition of trace Si significantly refined the Cr-rich precipitates of the Cu-Cr alloy but did not appreciably promote the nu-cleation of the precipitated phase. The influence of trace Si on the Cr-rich precipitates was assessed in terms of the Si-Cr and Si-vacancy interactions. The first-principles calculations reveal that there exists a strong attraction between Si and Cr with an interaction energy of - 0.27 eV for the nearest neighbor, which could promote the formation of Si-Cr clusters in the early aging stage that serve as heterogeneous nucleation particles for precipitates and induce the refinement of body-centered cubic (bcc) Cr-rich precipitates, re-sulting in an increase in the yield strength of the Cu-Cr alloy. The strengthening precipitates of the Cu-Cr-Si alloy mainly consisted of fcc Cr-rich precipitates and bcc Cr-rich precipitates, the strengthening mechanisms of which were the dislocation shear mechanism and dislocation bypass mechanism, respectively. In terms of performance, the conductivity of the Cu-Cr alloy decreased with the addition of trace Si from 94.5% IACS to 92.5% IACS, the yield strength increased from 178 MPa to 193 MPa, and the stress relaxation rate de-creased from 18.93% to 15.27%. The improvement in the stress relaxation resistance of the Cu-Cr alloy with the addition of trace Si was mainly attributed to the drag effect of the element on dislocation movement and the refinement effect of the element on Cr-rich precipitates.(c) 2023 Elsevier B.V. All rights reserved.