Research on lamellar structure and microhardness in directionally solidified ternary Sn–40.5Pb–2.6Sb eutectic alloy

Sn–40.5 wt%Pb–2.6 wt%Sb ternary alloy was directionally solidified with a constant temperature gradient (G = 18 K/mm) and growth rates ranging from 1 μm/s to 30 μm/s. Experimental results indicated that the lamellar structure consisted of Pb-rich and Sn-rich phases. The lamellar spacings (λ) and microhardness (HV) were measured and the HV increased with increasing growth rate (V) or decreased with increasing lamellar spacing. The dependences of λ and HV on V were determined by using a linear regression analysis. The relationships between the λ, V and HV were given as: λ=3.39V−0.51λ=3.39V−0.51, HV=12.65V0.11HV=12.65V0.11 and HV=16.42λ−0.2HV=16.42λ−0.2, respectively. The fitted exponent values were in accordance with the previous experimental results obtained from Sn–Pb alloys and In–Bi–Sn ternary alloys.