Effect of cell morphology on mechanical properties of closed cell metal foams and usability of photoelasticity method

In this study, effects of cell morphology on the mechanical properties of Albasedclosed cell metal foams were investigated. AlSi8Mg0.8 alloy closed cell metallic foams were produced by Powder Metallurgy (PM) route. By weight of Al, 8% Si, 0.8% Mg and 0.8 - 1.2% TiH2 powders were mixed in a three dimensional Turbulo for 45 min. Mixed powders were compacted at roomtemperature under 300 MPa pressure and sintered at 500 oC for an hour and then hot extrusion process at the rate of 8:1 with 450 oC was applied. Extrudedmaterials were rolled up to 50 % hot / warm deformation rate at 400 oC and also plate-shaped preform plate samples which are ready to foam wereproduced. Preform plate materials were foamed at 720 and 760 oC furnacetemperatures after placed in foaming mold with and without pre-heated. By this way, metallic foams were produced in three different density and three different cell Compressive stress distrubution of Al based metallic foams under different compressive elastic stress were investigated by photostress method.Generally, microstructure of the foam cell walls was consisted of ?-Al dendrite phase, Al-Si eutectic structure, primary Si, Ti dissolved in the structure and metastable hexagonal ß'-Mg2Si precipitates. As a result of compression deformation of metallic foams, the type of fracture and collapse mechanism were changed by differences in cell size and shape factor of foam materials with about same density. Compression strength of the foam materials in same density decreased with increasing cell size. However, it increased for foam materials have close to ideal shape factor. The stress distribution up to yield stress formed on the cell wall could be determined with Photoelasticity method.Keywords : Metalic foam, Al foam, Closed cell, Shape factor, Cel size, Photoelasticity method, Compressive strength