泡沫铝无增粘发泡下的稳定成形机制及强韧机理研究

Owing to the combination of excellent performances, such as vibration attenuation, impact protection and electromagnetic shielding, aluminum foam is given potential value of scientific research and application prospects. However, these potential applications are limited by its brittle compressive property. For this purpose, this project intends to adopt non-viscosification foaming technology, where single foaming agent will be replaced by the foaming mixture, so as to realize the fabrication of aluminum foam without thickening process. Firstly, the foaming mixture will be prepared by grinding metal particles, foaming agent and reinforcement phase using a ball grinder, after that the thermal decomposition behavior of foaming mixture and the dispersion mechanism of reinforcement phase will be studied. Secondly, SEM and TEM technologies will be adopted to investigate the influence of foaming mixture on the bubble nucleation and pore wall microstructure, revealing the stability mechanism of liquid foam based on the non-viscosification fabrication route. Finally, to reveal the strength and toughness mechanism of aluminum foam and regulate its energy absorption properties, pore structure and compressive test of the fabricated aluminum foam will be studied, including the deformation behavior, crack initiation and propagation, where the DIC and fracture analysis technology will be adopted. This project is expected to solve production of aluminum foam, provide a theoretical foundation for the non-viscosification production of aluminum foam, and has important academic significance and engineering application value.

阻尼减震、冲击防护、电磁屏蔽等多种优异性能赋予泡沫铝巨大的科研价值和广阔的应用前景。然而，低强脆性的压缩特性限制了泡沫铝在各工业领域的应用。为此，本项目拟采用无增粘发泡技术，用发泡混合体替代单一发泡剂，实现泡沫铝材料在铝熔体无增粘状态下的发泡成形。首先，拟以金属颗粒为载体，连同发泡剂及增强相混合球磨制备发泡混合体，并研究其热分解行为及增强相的分散机制；其次，辅助以SEM、TEM技术研究发泡混合体对熔体内气泡形核和孔壁微观组织的影响规律，进而揭示铝熔体在无增粘状态下的泡沫稳定机制；最后，统计分析无增粘泡沫铝的孔隙结构，并进行性能测试，运用DIC手段及断口分析技术研究材料的变形行为、裂纹的萌生与扩展模式，揭示泡沫铝的性能强韧机理，最终实现无增粘泡沫铝吸能特性的调控。本项目可为泡沫铝的无增粘生产提供理论支持，具有重要的学术意义和工程应用价值。

泡沫铝材料是一种集多种优异特性于一体，具有极为广阔应用前景的轻质多孔材料，但脆性的压缩特性及失效模式限制了其在诸多现代工业领域的应用。为此，本项目提出并围绕泡沫铝材料的无增粘发泡技术展开深入研究，揭示无增粘发泡工艺中液态孔泡的稳定机制，分析所制备高韧无增粘泡沫铝的力学性能。具体研究结果表明如下：球磨后的发泡混合体可实现细小TiH2/CaCO3在铝颗粒表面的吸附、镶嵌，发泡混合体热分解呈现典型双峰形貌，分别是480°C ~ 560°C的TiH2释氢吸热峰和650°C ~ 675°C的铝颗粒熔化吸热峰，添加CaCO3后出现典型放热峰为CO2与Al之间的氧化反应，改变发泡混合体内TiH2/CaCO3的配比含量可实现峰值的调控。研究以发泡混合体FMx和FM2Cx进行无增粘泡沫铝的制备，分析了发泡混合体对泡沫铝内部孔隙结构、底部无泡层的影响，发泡混合体内Al颗粒的增加，可促进总体高度，减小无泡层厚度；微量CaCO3的可促进孔泡稳定性，过量则会恶化发泡效果及孔隙结构。无增粘发泡过程中Al颗粒可作为短暂增粘剂提高液膜的稳定性，而FM2Cx中微量CaCO3可促使孔泡内氧化膜的自修复提高孔泡稳定性。力学性能测试表明无增粘泡沫铝呈现较为光滑的压缩应力-应变曲线，较传统增粘泡沫铝本项目制备的AF-FM和AF-FM2C可承受最大约2倍的弯曲挠度变形，且AF-FM弯曲吸能强于AF-Ca材料，微量的CaCO3添加可提高材料的最大弯曲强度；无增粘泡沫铝断口多见较大尺寸韧窝，呈现典型的韧性断裂形貌，且孔泡薄膜区域可见明显颈缩变形痕迹。无增粘泡沫铝的发泡稳定机制揭示及其韧性失效模式有助于充分发挥泡沫铝的优良吸能特性，对推动其在各领域的工业化应用具有较为重要的研究意义。