Cellular spacing selection of Al-0.53Zn alloy under near-rapid directional solidification condition

In order to investigate the response of primary cellular/dendritic spacing selection to the variation of growth velocity under near-rapid directional solidification condition, an Al-0.53Zn alloy is directionally solidified with Bridgman apparatus. The results show that at the given temperature gradient the microstructures is cells and there exists a wide distribution range of cellular spacing. The maximum, λ_max, minimum, λ_min, and average cellular spacing, λ̄, as functions of growth rate, v, can be given by λ_max=948.51 v^-0.4961, λ_min=661.16 v^-0.5015, λ̄=412.41 v^-0.5049, respectively. The experimental results are compared with that predicted by the current KGT model, and a good agreement is found. Moreover, it is found that the average cellular spacing is also remarkably history-dependent.