CALPHAD-guided Optimization of the Microstructure of Sn–Sb–Cu Bearing Alloys

The increasing Cu content of Sn-11Sb-xCu (wt.%, x = 0, 2, 4, 6) bearing alloys promotes the growth of ordered Sn3Sb2, and Sn3Sb2 with the maximum mean diameter (161.3-177.3 mu m) is observed in Sn-11Sb-6Cu alloy. Gravity-driven aggregation of Sn3Sb2 occurs in the top region of Sn-11Sb ingot. The inhomogeneous distribution of Sn3Sb2 driven by density difference between Sn3Sb2 and matrix is suppressed with Cu addition due to the formation of Cu6Sn5 with a density of 8.06 g/cm(3), and homogeneous microstructure is obtained in Sn-11Sb-xCu alloys (x = 2, 4, 6). Sn3Sb2 changes from regular cube morphology to irregular morphology with Cu content reaching 6 wt%. The relatively high Cu content in liquid leads to the nucleation of Cu6Sn5 around the liquid/Sn3Sb2 interface. Cu6Sn5 inside Sn(3)Sb(2 )can thus effectively affect the growth direction of Sn3Sb2, and finally lead to the formation of Sn3Sb2 with irregular morphology. The influence of Cu on microstructure evolution of Sn-Sb-Cu bearing alloys is revealed with the guidance of phase diagram calculation (CALPHAD), which can contribute to the further optimization of Sn-Sb-Cu and other bearing alloy.