Microstructure evolution and composite strengthening mechanism during solid solution and aging treatment for Cu-Ni-Co-Si sheet

A type of Cu-Ni-Co-Si alloy was designed and conducted by solid solution and aging treatments. Meanwhile its microstructure evolution and performance evolution were also studied. The characteristics of precipitated phases after aging treatment, and the strengthening mechanism of the process have been thoroughly studied. The results indicate that the optimal process for Cu-Ni-Co-Si alloy is solid solution at 900 °C for 120 min and aging at 500 °C for 240 min, respectively. At peak aging, the alloy reached tensile strength and conductivity of 631 MPa and 41.3 % IACS, respectively. The grain orientation of the aged alloy is complex; besides it is equiaxed; and there are a large number of twins and dislocation lines in the crystal. The matrix contains both Co2Si large-grained precipitated phases and orthorhombic, nanoscale precipitated phases of (Ni,Co)2Si; with sizes in the range of 5–8 nm. (Ni,Co)2Si is the main strengthening phase of the alloy after aging treatment due to its fineness and diffuseness. Solid solution and aging treatment improve microstructure and comprehensive properties of materials, and validated the theoretical guidance and feasibility in practical applications through high-precision quantitative calculations.