粉末冶金泡沫铝泡孔演化的研究

Study on Pore Evolution of Al Foams Prepared by Powder Metallurgy

着重研究了粉末冶金法泡沫铝在不同发泡时间下的泡孔形貌和泡孔内表面褶皱的变化.结果表明:随着发泡时间的延长,气泡由近球形泡孔向多边形泡孔演化,布拉德边界逐渐变小和泡壁更薄,并出现了泡壁局部断裂以至于泡孔破裂并合并;早期的类裂纹孔是粉末冶金发泡过程中的固有特征,这是由粉末冶金前驱体内部存在的垂直于压制方向的内应力释放所造成的;泡孔内的褶皱反映了泡孔结构的演化过程,发泡前期泡孔内表面比较光滑,存在少量的褶皱,发泡中期内表面的褶皱以凸起为特征,后期由于重力作用的加剧和泡孔表面能的进一步升高,形成了带状褶皱的形貌.

Changes in pore morphology and wrinkles on the inner surface wrinkling of pores of Al foams prepared by powder metallurgy（PM）were investigated for different foaming time.The results showed that the bubble shape evolves from near spherical pores to polygonal ones with foaming time.With Plateau borders become smaller gradually,cell walls get thinner,even local fracture and,finally,the inevitable rupture and coalescence of pores.The crack-like pores found in the early foaming process is just the inherent characteristics of Al foams prepared by PM,which are caused by the release stressing in the direction perpendicular to compacting load inside the PM precursors.The pore evolution process is reflected by the wrinkles on its inner surface,i.e.the inner surface is rather smooth with a few wrinkles in the early foaming process,then the wrinkles are bulging out and,at last,the wrinkle belts form on the inner surface due to gravitational effect and increasing surface energy.