Effect of specific pressure on the microstructure, tensile and tribological properties of semi-solid squeeze casting CuSn20P1 alloy

CuSn20P1 alloy was fabricated via semi-solid squeeze casting under various specific pressures (0–150 MPa). As the specific pressure increased gradually from 0 MPa to 150 MPa, the α-Cu dendrites disappeared and the grain size decreased. Meanwhile, higher specific pressure effectively alleviated the segregation of Sn, leading to a reduction in the amount of the δ-Cu 41 Sn 11 phase and an increase in the content of β′-Cu 5.6 Sn, which contributed to the improvement of mechanical properties. Calculation results indicated that Cu 3 P, δ and β′ are all ductile stable phases with metallic characteristics and exhibit anisotropy. The order of hardness and Young's modulus values was consistently Cu 3 P >δ >β′, which agreed reasonably well with the measured values within acceptable error margins. Mechanical property evaluations revealed that both the ultimate tensile strength (UTS) and elongation (EL) of the alloy reached their maximum values at 150 MPa, measuring 366.9 MPa and 0.52 %, respectively. These values represent improvements of 64.68 % and 156.16 % compared to those of the alloy prepared at 0 MPa. The alloy processed at 150 MPa also demonstrated the best wear resistance. As the specific pressure increased from 0 MPa to 150 MPa, the coefficient of friction (COF) and wear rate decreased from 0.483 to 2.01 × 10 −4 mm 3 /N·m to 0.341 and 0.601 × 10 −4 mm 3 /N·m, corresponding to reductions by factors of 1.42 and 3.34, respectively. Therefore, this study provides both an experimental basis and theoretical support for the design and application of high-Sn (Sn > 10 wt%) cast copper alloys with excellent mechanical properties.