Compressive Behavior of Porous Metals with Aligned Unidirectional Pores Compressed in the Direction Perpendicular to the Pore Direction

The compressive behavior of porous A6061 alloy with aligned unidirectional pores was investigated. Porous specimens with various sizes and relative thicknesses (thickness t/length l) of cell walls were prepared via machining after various heat treatments. Compression tests were conducted on porous specimens in the direction perpendicular to the pore direction. Distributions of the equivalent plastic strain were obtained using digital image correlation. Finite element analyses were also conducted to obtain the stress and strain distributions. The compressive stress σ increased with the increase in the compressive strain, and the increase in σ was then suppressed. Using a newly constructed deformation model, it was revealed that a plateau region was initiated by the plastic collapse of the cell walls. After the occurrence of the plastic collapse, three deformation modes were found in the compression of the specimens with various t/l. These modes transitioned from plastic buckling to fracture, and then to rapid densification without plastic buckling and fracture, depending on t/l. The sharp increase in the horizontal strain and the suppression of the decrease in the porosity occurred simultaneously when σ increased sharply again, irrespective of the structure and heat treatment of the specimens; this was observed as the plateau end.