Precipitation Behavior and Strengthening Effects of the Cu-0.42cr-0.16co Alloy During Aging Treatment

The precipitation behavior and strengthening effects of the Cu-0.42Cr-0.16Co alloy aged at 450 °C was investigated using atom-probe tomography, transmission electron microscopy, and hardness and electrical conductivity measurements. The results showed that the fine FCC Cr-rich precipitates with a cube-on-cube orientation relationship (OR) were formed by Cr and Co enrichment at the early aging stage, semi-coherent with the Cu matrix. The OR transformation of the FCC Cr-rich precipitates from the cube-on-cube OR to the OR of (2¯20)Cu//(2¯20)Cr, [112]Cu//[110]Cr occurred with prolonging the aging time. The OR transformation decreased the mismatch degree along the [111¯]Cu and [112]Cu crystallographic directions and produced a strain difference along different crystallographic directions. Thus, some ellipsoid precipitates were formed in the Cu-Cr-Co alloy during aging. In the peak-aged stage (aged for 8 h), the aging strengthening of the Cu-Cr-Co alloy was mainly attributed to the precipitation of the FCC Cr-rich particles, and the strengthening was controlled by the Orowan mechanism. The peak-aged alloy exhibited a larger size of precipitates than the alloy aged for 4 h, inducing a stronger precipitation strengthening effect (∼153 MPa).