Nondestructive observation of compression behavior of pores in three-layered functionally graded aluminum foam of A1050/A6061/ADC12 by X-ray computed tomography

Functionally graded aluminum foam (FG Al foam), in which the properties vary with the position, is expected to improve the performance of Al foam. In this study, A1050/A6061/ADC12 three-layered FG Al foam was successfully fabricated by a friction stir welding route precursor foaming method. Stepwise compression tests and continuous X-ray computed tomography (CT) nondestructive observation of the pore structures of the FG Al foam was conducted. It was revealed that the deformation of the fabricated FG Al foam started from the low strength A1050 Al foam layer, and thereafter the middle strength A6061 and high strength ADC12 Al foam layers sequentially deformed. The stress-strain curves during compression tests revealed that three plateau regions appeared independently in the FG Al foams, which corresponded to the plateau regions appearing in the uniform Al foams. The three plateau regions of the FG Al foam had almost the same plateau stresses as that for each corresponding uniform Al foam. These results suggest that the FG Al foam has the potential to be deformed at a controlled and desired location and with a desired plateau stress.