闭孔泡沫铝材料制备过程中气泡的形成与演化

以熔体直接发泡法制备闭孔泡沫铝材实验为基础,通过获得不同实验阶段的泡沫铝样品,以及对实验样品切面或断面进行观察和分析,描述了在熔体发泡法制造泡沫铝过程中TiH2加入熔体后的分解过程,原始气泡的形成方式以及产生的气泡和未分解TiH2的存在状态;解释了气泡进一步长大的原因和未分解的TiH2如何释放气体;表述了气泡的合并和无泡层的形成.结果表明:未分解的TiH2颗粒粘附在熔体内形成的较小气泡表面,即气/液相界面上;在恒温发泡过程中气泡壁上吸附的尚未分解的TiH2颗粒进一步分解并向气泡内释放气体,使气泡长大;相邻气泡壁上的TiH2局部浓度较高并集中释放气体,导致气泡壁破裂及气泡间的合并.

Formation and evolution of bubble in fabricating closed-cell aluminum foam

The closed-cell aluminum foam was fabricated by direct foaming in melt. Through sampling aluminum foam in different stages the cross-section of them were observed and analyzed. It was explained how TiH_2 was decomposed after entered into the melt, how initial bubbles were formed and what was the state that generated bubbles and undecomposed TiH_2 lay in. The reason that why bubbles grew and how the gas was released from undecomposed TiH_2 were stated. The merging of bubbles and formation of bubble-free layer were also described. The results show that the particles of undecomposed TiH_2 adhere to the surface of small bubbles formed in the melt, that is on the surface of gas/liquid phase. During foaming of constant temperature, the particles of undecomposed TiH_2 adhering to cell wall decompose and release gas into bubbles and make them grown up. If the local concentration of TiH_2 of adjacent cell wall is high and it releases gas intensively, fracture of cell wall and merging of bubbles will be generated.