Primary cellular/dendritic spacing selection of Al-4.95% Zn alloy under near-rapid directional solidification condition

Al-4.95% Zn alloy is directionally solidified in a modified Bridgman apparatus with higher temperature gradient to investigate response of cellular/dendritic microstructures and primary spacing to the variation of growth velocity under near-rapid directional solidification condition. The results show that, with increasing growth rate, there exists a transition from dendrite to fine cell and a wide distribution range in primary cellular/dendritic spacing at the given temperature gradient. The maximum, γ_max, minimum, γ_min, and average primary spacing, γ̄, as functions of growth velocity, v, can be given by γ_max = 12 340 v^-0.8353, γ_min = 2953.7 v^-0.7717, γ̄ = 7820.3 v^-0.8333, respectively.