SOLIDIFICATION CHARACTERISTICS AND MICROSTRUCTURAL EVOLUTION OF Zn-1.26 wt.% Al ALLOY

Zn–1.26 wt.% Al alloy was directionally solidified upward with a constant growth rate (V = 16.6 μm/s) in a wide range of temperature gradients (G = 1.94–5.15 K/mm) and with a constant temperature gradient (G = 5.15 K/mm) in a wide range of growth rates (V = 8.3–500 μm/s) with a Bridgman-type directional solidification furnace. Microstructure parameters, the primary dendrite arm spacing (λ1), secondary dendrite arm spacing (λ2) and dendrite tip radius (R), were measured and expressed as functions of G and V by using a linear regression analysis method. It was found that the values of λ1, λ2 and R decrease with increasing values of V and G. The experimental results were compared with the main predictive theoretical and experimental works for dendritic spacings.