The Dependence of Lamellar Spacings and Microhardness on the Growth Rate in the Directionally Solidified Bi-43 wt. percent Sn Alloy at a Constant Temperature Gradient

摘要

Bi-43 wt. percent Sn eutectic samples were directionally solidified upward with five different growth rates (V = 8.3-164.8 mum/s) at a constant temperature gradient (G = 3.55 K/mm) in a Bridgman type directional solidification furnace. The lamellar spacings (lambda) and microhardness values (H_V) were measured from the quenched samples; the directionally solidified Bi-43 wt. percent Sn eutectic alloy and the minimum undercoolings (DELTA T) were determined from the Jackson-Hunt eutectic theory. The dependency of lamellar spacings (lambda), microhardness (H_V) and undercooling (DELTA T) on the growth rate (V) were analyzed. According to these results, it has been found that the value of lambda decreases with the increasing value of V and that the values of H_v and DELTA T increase for a constant G. The values of lambda~2 V, lambda DELTA T and DETLA T V~(0.5) were determined by using the values of lambda, DELTA T 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.