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通过对Sn-36%Ni包晶合金在恒定温度梯度(G=20 K/mm)下进行的一定速度范围内(v=2～200μm/s)的定向凝固实验,研究凝固组织特征尺度随生长速度v的变化;测量包括一次与高次枝晶间距及枝晶尖端半径在内的凝固组织特征尺度。通过实验结果与理论模型的对比,发现凝固组织特征尺度随生长速度的变化关系为:对于一次枝晶间距有λ1=335.882v-0.21,且与Kurz-Fisher模型吻合;对于二次枝晶间距有λ2=44.957v-0.277,且与Bouchard-Kirkaldy模型吻合;对于三次枝晶间距有λ3=40.512v-0.274;对于枝晶尖端半径有R=22.7v-0.36。实验结果表明,λ1/λ2随着生长速度的增加而增加,λ1/λ3的变化明显较λ1/λ2的小,表明三次枝晶具有与一次枝晶类似的生长特征;而λ1/R的比值随着生长速度的增加而由2增加到2.3,变化很小。
The directional solidification experiments of Sn-36% Ni peritectic alloy at a constant temperature gradient (v = 2 ~ 200μm / s) at constant temperature gradient (G = 20 K / mm) The change of the velocity v, and the measurement of the characteristic scale of the solidification structure including the distance between the primary dendrite and the radius of the dendrite tip. By comparing the experimental results with the theoretical model, it is found that the relationship between the characteristic scale of solidified tissue and the growth rate is as follows: λ1 = 335.882v-0.21 for the primary dendrite spacing, which is consistent with the Kurz-Fisher model; for the secondary dendrite spacing λ2 = 44.957v-0.277, and it is consistent with the Bouchard-Kirkaldy model; λ3 = 40.512v-0.274 for the triple dendrite spacing; and R = 22.7v-0.36 for the dendrite tip radius. The experimental results show that λ1 / λ2 increases with the increase of the growth rate, and the change of λ1 / λ3 is obviously smaller than that of λ1 / λ2, indicating that the tertiary dendrites have the similar growth characteristics as the primary dendrites. The ratio of λ1 / R The growth rate increased from 2 to 2.3, with little change.