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 μm/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 ( λ) and microhardness ( H V) were measured from both transverse and longitudinal sections of the samples. The dependence of eutectic spacings ( λ) 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 λ 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 ( λ 2 V) were also determined by using the measured values of λ and V. The results obtained in present work were compared with the previous similar experimental results obtained for binary and ternary alloys.