Abstract In order to investigate the response of primary cellular/dendritic spacing selection to the variation of growth velocity under near-rapid directional solidification condition, anAl-0.53Zn alloy is directionally solidified with Bridgman apparatus. The results show that atthe given temperature gradient the microstructures is cells and there exists a wide distributionrange of cellular spacing. The maximum, A..., minimum, and average cellular spacing,A, as fullctions of growth rate, v, can be given by λmax=948.51v(-0.4961),λmin=661.16 v(-0.5015),λ=412.41 v(-0.5049), respectively. The experimental results are compared with that predicted bythe current KGT model, and a good agreement is found. Moreover, it is found that the averagecellular spacing is also remarkably history-dependent.
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