Production of aluminum based spherical foams by powder metallurg route and investigation of their production parameters

In this study, aluminum based spherical shape foams were produced by using powder metallurgy techniques. Effect of production parameters such as; foaming temperature, foaming time, amount of foaming agent and deformation rate on the production of foam were determined. In experimental study, various amount of powdered foaming agent (0.5, 0.75, 1, and 1.5% TiH2) were added to Alumix 231 powder and mixed for 30 minutes. Mixed powders were compacted at 600 MPa pressure by using a uniaxial action press to produce powder blanks. Blanks were then preheated to 550 oC in a furnace for 180 min and then deformed by 10, 30, 50 and 70% and then cut into square shape to produce spherical foams. Samples were foamed without any mold at 650oC, 670oC, 690oC and 710oC between 2 to 5 minutes with the interval of 30 seconds. Effect of production parameters on the pore size, shape, linear expansion and density of spherical shape aluminum foam were investigated. It was found that pore size, linear expansion rate and the amount of porosity increased with increasing the deformation rate (70%) however, it reduced the pore number. Increasing the foaming temperature, foaming time and the amount of foaming agent together, resulted in inhomogeneous pore structure together with collapsing of foam structure. This also reduced the amount of porosity and linear expansion rate of the foams. Choosing a suitable parameters (such as 690 oC foaming temperature, 1% TiH2 foaming agent and 3-3.5 min foaming duration) resulted in a positive effect on foamability.