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The Cu-4Sn and Cu-4Sn-0.15P alloys with rod diameter of 12.5 mm were prepared and then cold drawn to 2.6 mm via multi-pass drawing. The microstructure evolutions, mechanical properties, and electrical conductivity of Cu-4Sn and Cu-4Sn-0.15P alloys were comprehensively analyzed using optical microscope, scanning electron microscope, tension test and electrical conductivity tester. As compared with the P-free alloy, the addition of P can form a new kind of P-rich phase in the Cu-4Sn alloy, and thus refine the casting microstructure via pinning the grain boundary. The toughening mechanisms of P-rich phases in Cu-4Sn-P alloy wires during cold drawing were investigated. With accumulative drawing strain, the spherical P-rich phase gradually changes into fibrous phases, which thus introduce obvious fiber reinforced strengthening. In addition, the distribution of P-rich phase also enhances the< 111 > texture, and promotes the growth of fragmentation zone. It contributes to an improved ultimate tensile strength and final elongation from 664.5 MPa and ∼ 0 % in Cu-4Sn alloy to 970.5 MPa and 1.53 % in Cu-4Sn-0.15P alloy. Finally, the conductivity for Cu-4Sn-0.15P decreases slightly owing to the intensified electron scattering with high amount of primary phase after the addition of P element. • Adding P to Cu-Sn alloy results in more uniform grain size, while increasing dendrite segregation. • Cu-4Sn-0.15 P alloy wire present more homogeneous distribution of P-rich phases with P content of 9 wt%. • Spherical P-rich phases evolve into fibrous shapes, contributing to higher strength and better elongation. • The addition of P increases the proportion of grain fragmentation during drawing. [ABSTRACT FROM AUTHOR]

• The radii of the nanoscale precipitates are dramatically smaller in the annealed Cu-2Ag-0.14La alloy than in the annealed Cu-2Ag alloy. • The grain size of annealed Cu-2Ag-0.14La alloy is always smaller than that of the annealed Cu-2Ag alloy from 400 °C to 650 °C. • Precipitation strengthening of nanoscale precipitates in the matrix and grain-boundary strengthening during grain refinement substantially improve the yield strength of the Cu-2Ag-0.14La alloy. [Display omitted] A new Cu–2Ag–0.14La alloy is developed to enhance the mechanical property and electrical conductivity with inducement of Ag-rich primary phases and finer nanoscale Ag precipitates. The microstructural evolution and mechanical properties of Cu–2Ag–0.14La and Cu–2Ag alloys obtained by drawing and annealing were then summarized and analyzed. The results indicate that both the yielding and ultimate tensile strengths of annealed Cu–2Ag-0.14La alloy were reinforced after La modification. The average grain sizes of two alloys increase during annealing, but the size ratio (R Cu-2Ag-0.14La /R Cu-2Ag) dramatically varies with rising the heat temperature, evolving from 70.48% at 400 °C to 43.78% at 650 °C. Meanwhile, it is found that the refined grains sizes in Cu-2Ag-0.14La alloy are closely related to the nano-scale precipitates (~450 nm), which hinder the formation of subgrain boundaries at 400 °C, and impose a stronger pinning effect on boundary migration of recrystallized grains during annealing (≥ 450 °C). Consequently, higher hardness and electrical conductivity are contributed by grain refinement and dispersion strengthening of the nanosized phases. [ABSTRACT FROM AUTHOR]