泡沫铝发泡初期孔隙及气泡的形成与扩展

通过采用粉体致密化浸入式快速加热新工艺制备泡沫铝技术，研究了泡沫铝发泡早期气泡形成特征、早期气泡孔径结构特点及动态变化规律。结果表明：泡沫铝发泡历经以微膨胀、显著膨胀和塌陷收缩为特征的3个主要阶段；在发泡初期，微膨胀形成的机制主要是TiH2分解的H2，并受其受力状态所决定的，由此形成的裂纹式孔隙主要在固态，扩展方向呈横向特征。预制块的显著膨胀主要是由于TiH2的持续分解使裂纹式孔隙扩展长大的结果。由于新工艺加热升温迅速，发泡时间由一般的10min缩短为30—150s，使预制块固液态转换时间大大缩短，有效地提高了均匀发泡的动力学条件，同时还提高了TiH2的利用率。

Formation and Propagation of Gas Hole in Initial Stages of Foam in Foamed Aluminum

Formation characteristics, aperture configuration and dynamic change of gas hole in the early stages of foamed aluminum were investigated based on preparation of foamed aluminum by a new powder metallurgy method with immersing preformer and heating up rapidly. The results show that foaming process is characterized by micro-propagation to macro-propagation to collapse. The formation mechanism of micro-propagation of crack-gas-hole depends on the stress from H_2 decomposed from TiH_2, characterized by transverse crack in propagation direction and distributed within solid phase. Macro-propagation is attributed to the crack propagation and growth resulting from continuous decomposition of TiH_2. The new method can reduce the heating time from 10 min to 30~150 s, which effectively increase the dynamic mechanism of homogeneous foaming and improve the utilization ratio of TiH_2.