Micro-structures and properties of ultra-high strength Cu-Ni-Si-Mg-Cr alloy

Microstructure and properties of the Cu-6.0Ni-1.4Si-0.15Mg-0.1Cr alloy are studied by optical microscope, X-ray diffractometer and transmission electron microscope observation, and by Vickers hardness tester, eddy-current electrical conductivity measurement. Results show that the developed dendrite which can be divided into dendrite area, the middle transition region and non-equilibrium solidification phase particles, appears in the casting ingot. The non-equilibrium solidification phases are δ-Ni₂Si and β-Ni₃Si. The main strength mechanism for designed alloy is precipitation strengthening and the strengthening phases are δ-Ni₂Si. After appropriate thermo-mechanical treatment, the hardness of the alloy can be 353 HV, tensile strength can reach 1 010 MPa, and yield strength is 930 MPa with enlogation being 3.8% and electrical conductivity being 29.7% IACS.