Microstructure and properties of high-strength Cu–Ni–Si–(Ti) alloys

The tradeoff between the strength and the fracture elongation in the high-strength Cu-Ni-Si alloy became a hot research topic recently.Cu-Ni-Si-(Ti) alloys were fabricated in a vacuum induction melting furnace to study the effects of titanium on the microstructure and mechanical properties of Cu-Ni-Si alloys with different thermo-mechanical treatments.After homogenization at 900℃ for 4 h,hot-rolled by 80%,solution treatment at 970℃ for 2 h,cold-rolled by 50%,and finally aged at 450℃ for 180 min,the studied Cu-10 Ni-Si-2 Ti alloy achieved the hardness of HV 252.4,electrical conductivity of 23.6% IACS,tensile strength of 764.4 MPa,yield strength of 622.26 MPa,fracture elongation of 10.4%,and strength-elongation product of 7.95 GPa%,which are less than those of the studied Cu-10 Ni-2 Si alloy.The addition of Ti contributed to refining the microstructure,suppressing the decreasing trend in mechanical properties after peak hardening,and arousing a primary substructure strengthening mechanism rather than the precipitation strengthening in Cu-Ni-Si alloys.These findings provide essential understandings of the effects of the Ti on Cu-Ni-Si system alloys,and the designed Cu-Ni-Si alloys with highstrength and fracture elongation could fulfill some requirements of the electronic and electrical industry.