Functionally graded (FG) porous aluminum (Al), consisting of a high porosity layer and low porosity layer in a single porous Al, was fabricated by a friction stir welding (FSW). From X-ray computed tomography (CT) observations of the pore structures of fabricated FG porous Al, it was found that the fabricated FG porous Al had two layers with high porosity of large pore diameter layer and low porosity of small pore diameter layer. From compression tests of the fabricated FG porous Al, the deformation started from the high porosity layer then spread to the low porosity layer. The stress–strain curves obtained in the dynamic compression tests revealed that the stress of the plateau region was lower during the deformation of the high porosity layer than that during the deformation of the low porosity layer. The stresses and absorbed energies in those two plateau regions during such deformations were almost the same as those of the uniform porous Al.

Microstructure and mechanical properties of Al–10Si–0.4Mg (mass%) alloy (AlSi10Mg alloy) specimens fabricated using selective laser melting (SLM) combined with powder-bed system have been examined. Optical microscope was used to identify the characteristic scalloped microstructure derived from local melting and rapid solidification of alloy powder during SLM process. The results of microscopy observation revealed that columnar α-Al grains subdivided by eutectic fine Si particles were elongated to the solidification direction depending on the radial heat flow caused by SLM process. The observed {100} texture along the building direction was attributed to the preferential [100] growth direction of α-Al phase in liquid. On the basis of the experimental results and thermodynamic analysis, the formation process of microstructure in the fabricated sample was discussed. The tensile strength of the fabricated specimen is 480 MPa, which is independent of the specimen geometry associated with the building direction, whereas the specimen tensile-deformed normal to the building direction exhibits a lower tensile ductility, which would be responsible for the fracture in the vicinity of melt pool (locally melted and rapidly solidified regions) boundaries.

Effect of anodizing time on the multiscale porous structure of the inner wall of the microchannel produced in a titanium alloy body has been investigated. The microchannel was produced by a powder-metallurgical process in which a titanium-powder compact containing thin aluminum wire was sintered at a temperature above the melting point of aluminum. During sintering, microscopic infiltration of molten aluminum into the porosity of the compacted titanium powder and subsequent diffusion of aluminum into the titanium powder particles brought about the formation of a microchannel lined with Ti–Al alloy layer in the sintered body. The inner walls of the microchannels with uniform composition, Ti–18.0(±1.8)mol%Al, were provided for anodizing experiments. When the anodizing time was in the range from 1.8 to 28.8 ks, the structure of the anodic oxide film was nanotube array. Each specimen had a microchannel of several hundred micrometers in diameter, inner wall asperity of several ten micrometers in size, and nanotube array structure of the anodic oxide film. In the specimen anodized for 59.6 ks, on the other hand, the nanotube array had changed to a different structure resembling that of nanoporous metals produced by dealloying.