Structural uniformity is an important parameter influencing physical and mechanical properties of lotus-type porous metals prepared by directional solidification of metal-gas eutectic (Gasar). The effect of superheat on structural uniformity as well as average porosity, pore morphology of porous metals was studied. The experimental results show that, when the superheat is higher than a critical value (ΔTc), the bubbling or boiling phenomenon will occur and the gas bubbles will form in the melt and float out of the melt. As a result, the final porosity will decrease. In addition, a higher superheat will simultaneously cause a non-uniform porous structure due to the pores coalescence and bubbling phenomenon. Finally, a theoretical model was developed to predict the critical superheat for the hydrogen to escape from the melt and the corresponding escapement ratio of hydrogen content. Considering the escapement of hydrogen, the predicted porosities are in good agreement with the experimental results.%结构均匀性是影响藕状多孔金属的物理和力学性能的重要参数。系统研究熔体过热度对金属−气体共晶定向凝固(Gasar)制备藕状多孔金属的多孔结构均匀性以及气孔率、气孔形貌的影响规律。实验结果表明，凝固过程中存在一临界过热度(∆Tc)，超过该临界值时，凝固界面前沿熔体中会发生气泡的形核和上浮溢出(“冒泡”或“沸腾”)现象，结果造成气孔率的下降。另外，过高的过热度会导致相邻气孔的合并粗化，形成大尺寸气泡，最终获得不均匀的气孔结构。在实验结果基础上，建立气泡溢出的临界过热度(ΔTc)理论模型和氢气溢出系数计算模型。在考虑氢气溢出时，理论预测的气孔率与实验结果吻合较好。
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