The dependence of lamellar spacings and microhardness on the growth rate in the directionally solidified Bi-43 wt.% Sn alloy at a constant temperature gradient

摘要

Bi-43 wt.% Sn eutectic samples were directionally solidified upward with five different growth rates (V = 8.3–164.8 µm/s) at a constant temperature gradient (G = 3.55 K/mm) in a Bridgman type directional solidification furnace. The lamellar spacings (λ) and microhardness values (HV) were measured from the quenched samples; the directionally solidified Bi-43 wt.% Sn eutectic alloy and the minimum undercoolings (ΔT) were determined from the Jackson-Hunt eutectic theory. The dependency of lamellar spacings (λ), microhardness (Hν) and undercooling (ΔT) on the growth rate (V) were analyzed. According to these results, it has been found that the value of λ decreases with the increasing value of V and that the values of HV and ΔT increase for a constant G. The values of λ2V, λΔT and ΔT V−0.5 were determined by using the values of λ, ΔT and V. The results obtained in the present work have been compared with those predicted by the Jackson-Hunt eutectic theory and with similar experimental results.