泡沫铝是一种以铝作为基体的多孔金属材料，同时具有多孔结构和金属的特性，是良好的吸能防护材料。基于不同原理的制备技术和性能研究，已经进行了很长时间，泡沫铝的几种主要制备技术都已发展得比较成熟，并获得了商业化应用。目前采用熔体发泡法制备的泡沫铝孔隙率通常大于80%，孔径大于3mm，平台应力一般小于5MPa，吸能能力小于2.5MJ/m3，较难满足高标准防撞吸能的需求。目前来说，减小泡沫铝的孔径和改善泡孔结构的均匀性是提高泡沫铝性能及其稳定性的有效途径，但采用熔体发泡法稳定可控地制备孔径在2mm以下，孔结构均匀的小孔径泡沫铝仍然存在很大的挑战。针对上述问题，本文从发泡剂，发泡工艺及熔体稳定性角度入手，进行了小孔径泡沫铝的制备工艺研究，并就小孔径泡沫铝的变形机制和吸能性能进行了系统的研究和比较。通过对TiH2在500℃空气中进行预热氧化处理（可将分解温度提高到500℃以上），并将其搅拌分散到AlMg35中间合金熔体中（熔体温度低于500℃），再将其冷却凝固后破碎的方式，得到了一种新型发泡剂AlMg35-TiH2。凝固后镶嵌在合金中的预热处理态TiH2颗粒与AlMg35中间合金完全润湿，并具有一定的距离，解决了TiH2与熔体润湿性差及允许搅拌分散时间短的问题。采用AlMg35-TiH2复合发泡剂时，在明确了不同粒径预处理态TiH2释气特性的基础上，研究了AlMg35-TiH2的在熔体中的熔化行为及AlMg35-TiH2复合发泡剂中TiH2的含量对发泡过程的影响。研究发现，复合发泡剂的颗粒尺寸大(5~8mm)、复合发泡剂中TiH2的含量低（5wt.%）、复合发泡剂中的TiH2颗粒粒径小（-400目，<38μm），有利于小孔径泡沫铝的制备。采用三维重构方法，研究了熔体发泡法制备的泡沫铝中典型的气泡合并方式，提出了可以通过增大扩散距离，延长液膜破裂时间，进而得到小孔径泡沫铝的制备思路。在此基础上，研究了采用AlMg35-TiH2复合发泡剂时，Ca添加量对气泡尺寸的影响，并制备出了孔隙率65%左右，孔径1mm左右的泡沫铝。针对泡沫铝用作防撞吸能材料的目的，研究了小孔径泡沫铝的变形过程及应力-应变曲线特征，随着泡沫铝孔径的减小（至1~2mm）及孔隙率的降低（至60~70%），泡沫铝的压缩应力-应变曲线的屈服应力提高到15~27MPa左右，吸能能力增加到10~15J/cm3左右，同时，应力平台段会产生向上的倾斜。针对现有应力-应变曲线特点，提出了一种单位质量吸能能力的表征方法，为泡沫铝的应用选择提供了参考。

Aluminum foams are a kind of porous material made from aluminum, which has characteristics of porous structure and metal at the same time and has been widely used in fields of energy-absorption and protection. Research on preparation technology and performance has been carried out for a long time. Several major preparation technologies of aluminum foams have been developed and commercialized. At present, the porosity of aluminum foams prepared by the melt foaming method is usually greater than 80%, the pore diameter is usually larger than 3mm, the plateau stress is generally less than 5MPa, and the energy absorption capacity is usually less than 2.5MJ/m3. Reducing the pore size of aluminum foams and improving the uniformity of the pore structure are effective ways to improve the performance and stability of aluminum foams. However, there still exist great technical challenges in preparing aluminum foams with pore diameter below 2mm through the melt foaming method. In view of above problems, this article starts from the perspective of foaming agent, foaming process and melt stability, and conducts a research on the preparation process of small pore aluminum foam, and studied the deformation mechanism and energy absorption performance of small pore aluminum foam.A new type of foaming agent AlMg35-TiH2 was developed by preheating TiH2 in air at 500℃ (The decomposition temperature can be raised above 500℃), and then dispersing it into an AlMg35 master alloy melt (The melt temperature is lower than 500℃). After solidification, the preheated TiH2 particles embedded in the alloy are separated and completely wetted with the AlMg35 master alloy, which solves the problem of uneven dispersion caused by poor wettability between TiH2 and melt. When using AlMg35-TiH2 composite foaming agent, on the basis of clarifying the outgassing characteristics of TiH2 with different particle sizes, the effect of the melting behavior of AlMg35-TiH2 in the melt and the TiH2 content in AlMg35-TiH2 composite foaming agent on the foaming process were also investigated. This study found that large granule size of the composite foaming agent(5~8mm), low content of TiH2 in the composite foaming agent (5wt.%) and small particle size of TiH2 in the composite foaming agent (-400 mesh, <38μm) are conducive to the preparation of small pore size aluminum foams. The three-dimensional reconstruction method was used to analyze the typical merging ways in the preparation of aluminum foam by the melt foaming method. This study shows that the merging is mainly caused by diffusion and liquid film rupture. In response to this phenomenon, ideas of extending the rupture time of the liquid film and increasing the diffusion distance in small pore aluminum preparation were proposed. On this basis, the effect of adding amount of Ca in the melt thickening process on the pore size was studied, and the small pore size aluminum foams with high porosity (pore diameter: ~1mm, porosity: 65%) were prepared.Aiming at the purpose of using aluminum foam as an energy-absorption material, the deformation process and stress-strain curve of small pore size aluminum foams were studied. With the decrease of pore diameter (to 1~2mm) and porosity (to 60~70%), the yield stress of aluminum foam in compressive stress-strain curve increases to about 15~27MPa, the energy absorption capacity also increases to about 10~15J/cm3, and at the same time, a slope (upward) in stress plateau section was observed. According to these characteristics of the existing stress-strain curve, a characterization method for energy absorption capacity per unit mass is proposed, which provides a reference for the application and selection of aluminum foams.