Primary cellular/dendrite spacing selection of Al-Zn alloy during unidirectional solidification

摘要

Al-4.95 wt/100 Zn alloy is directionally solidified with Bridgman apparatus to investigate response of cellular/dendrite microstructures and primary spacing to the variation of growth velocity. The results show that, with increasing growth rate, there exist a transition from dendrite to cell and a wide distribution range in primary cellular/dendrite spacing. The maximum, λ_max, minimum, λ_min, and average primary spacing, λ, as functions of growth rate, V, can be given by λ_max=4578V~-0.679, λ _min=1315.7V~-0.6543, λ =30.84.5V~-0.6982, respectively. The experimental results are compared with the Hunt-Lu model, and a reasonable agreement is found.