Research on the microstructure and properties of Cu-Ni-Si-Ti alloys with micro-nano hybrid systems

• Micron/nanoscale Ni 16 Ti 6 Si 7 and nanoscale Ni 2 Si precipitate in Cu-Ni-Si-Ti alloys. • Cu-Ni-Si-(Ti) alloys are mainly strengthened by fine nanoscale Ni 2 Si phases. • The micron Ni 16 Ti 6 Si 7 promotes the recrystallization nucleation of Cu. • Cu-4.84Ni-1.04Si-0.5Ti shows higher HDI stress from GNDs at G phase/Cu interfaces. The Cu-Ni-Si-Ti alloys with micron Ni 16 Ti 6 Si 7 phase and nano δ-Ni 2 Si dual-scale reinforcement particles were prepared and their microstructures, properties as well as strengthening mechanism were studied. It is found that micron-sized Ni 16 Ti 6 Si 7 particles (∼8μm) formed during alloy solidification, along with submicron Ni 16 Ti 6 Si 7 and Ni 2 Si precipitates (∼200 nm). This behavior differed from that observed in conventional Cu-Ni-Si alloys. After heat treatment, the micron and submicron Ni 16 Ti 6 Si 7 particles form semi-coherent interfaces with the α-Cu matrix, promoting recrystallization nucleation during hot rolling and thereby effectively refining the grain size of the alloy. Meanwhile, the nanoscale Ni 2 Si precipitates (∼30 nm) act as the primary strengthening phase, pinning grain boundaries and dislocations during deformation. Due to the significant elasticity modulus mismatch between Cu matrix and Ni 16 Ti 6 Si 7 phase, a large strain gradient during the tensile process will lead to HDI strengthening, and improve the overall performance of the material through the storage and induction of dislocations at the Cu grain boundaries and the Ni 16 Ti 6 Si 7 -Ni 2 Si/Cu interface. Therefore, compared with Cu-3.2Ni-0.7Si alloy, Cu-4Ni-0.9Si-0.5Ti alloy exhibits higher elastoplasticity while maintaining similar strength and conductivity. Its peak-aged conductivity reaches 35.0 ± 0 %IACS, with elastic modulus of 142 ± 4GPa, tensile strength of 747 ± 7 MPa, and elongation of 12.1 ± 0.3 %.