The microstructure parameters and microhardness of directionally solidified Sn-Ag-Cu eutectic alloy

Sn-Ag-Cu alloy of eutectic composition (Sn-3.5 wt.%Ag-0.9 wt.%Cu) was directionally solidified upward at a constant temperature gradient (G = 2.48 K/mm) in a wide range of growth rates (3.89-173.61 mu m/s) by using a Bridgman type directional solidification furnace. The eutectic microstructures were observed to be plate and rod form from the directionally solidified Sn-3.5 wt.%Ag-0.9 wt.%Cu samples. The values of eutectic spacings (lambda) and microhardness (H-V) were measured from both transverse and longitudinal sections of the samples. The dependence of eutectic spacings (lambda) and microhardness (H-V) on the growth rate (V) was determined by using linear regression analysis. According to these results, it has been found that, the value of lambda decreases with the increasing value of V and whereas, the value of microhardness (H-V) increases for a constant G. The values of bulk growth (lambda V-2) were also determined by using the measured values of lambda and V. The results obtained in present work were compared with the previous similar experimental results obtained for binary and ternary alloys (C) 2009 Elsevier B V. All rights reserved