基于挤出成形无约束条件下泡沫铝的发泡行为及气孔结构的演变

Foaming Behavior and Evolution of Cell Structure of Foamed Aluminum with Extrusion Forming Precursor Under Unconstrained Condition

通过实时摄像和断面图处理相结合方法,对热挤出成形无约束条件下的粉末紧实熔化法发泡工艺（简称PCM）及泡沫铝气孔结构的演变进行了研究。结果表明：加热速度（炉温）和试样温度（加热时间）是影响泡沫铝发泡行为和孔结构的主要因素;炉温为750℃、780℃、800℃、820℃时,发泡效果较好;炉温越高,试样的最大膨胀高度越高,孔隙率峰值越高,气孔更为圆整和均匀;预设炉温最佳范围为780～800℃,试样温度最佳范围为720～740℃,在此参数范围内,可得到最大孔隙率为77%、平均孔径2 mm、气孔圆整度为0.8的均匀孔结构的泡沫铝试样;发泡过程中孔结构的演化过程为：气孔形成、孔隙率不断增加,气孔大小和形状由小孔径球形、大孔径球形、多边形化、合并而至塌陷。

Through the method of real-time video and sectional drawing processing, the powder compaction melt foaming process（PCM） and the evolution of the foamed aluminum pore structure were studied under the unconstrained conditions of hot extrusion forming. The results show that the heating speed（furnace temperature） and the sample temperature（heating time） are the main factors which influenced foaming behavior and the pore structure. When furnace temperature is 750 ℃, 780 ℃, 800 ℃, 820 ℃, the effect is better. The higher the furnace temperature, the higher the biggest expansion height of the sample and the higher the peak value of porosity, pore is more rounded and uniform. The optimal range of preset furnace temperature is 780-800 ℃ and the best sample temperature is 720-740 ℃, during the scope of this parameter, the foamed aluminum with uniform pore structure can be obtained that is maximum porosity 77%, average pore diameter 2 mm,circular degree 0.8. The pore structure evolution process of the foaming process is that porosity forming and increasing, pore size and shape of small aperture spherical, large aperture spherical, polygons, merge and collapse.