Microstructure evolution and dislocation strengthening mechanism of Cu–Ni–Co–Si alloy

Abstract

An in-depth exploration of the microstructure evolution and characterization of the dislocation density in Cu–Ni–Si–Co alloy was performed using X-ray diffraction electron backscattering diffraction, transmission electron microscopy, three-dimensional atom probe technique, and high-energy X-ray diffraction (HEXRD). The results reveal that the tensile strength and electrical conductivity of the alloy are 937.27 MPa and 45.57% IACS, respectively, and that it has good stress relaxation resistance. There are many dislocation tangles, dislocation lines, dislocation cells, and deformation twins in alloys processed by cyclic cryogenic rolling and low-temperature aging. The alloy contains both 300–600 nm coarse particle precipitates and 5–10 nm rod-like nano-precipitated phases composed of (Ni, Co)2Si. The average dislocation density is (35.967 ± 1.513) × 1014 m−2, and the twin stacking-fault probability is 14.414 ± 0.333 × 10−3 in the alloy aged at 350 °C for 2 h.