Unidirectional-solidified 99.9% aluminum wires 6 mm in diameter have been produced by a heated-mold continuous casting process (OCC Process) at casting speeds of 0.33–5.0 mm/s. Effect of casting speeds on structures and crystal orientation of the cast wires has been studied by an EBSD technique. It was found that the crystal orientation of all cast wires parallel to the casting direction tended to be [001], the preferred growth orientation of aluminum. At lower casting speed (0.33 mm/s), unidirectional solidified structure wire exhibited single-like crystal morphology with low-angle tilting sub-grain boundaries. In this case, local disorientation angles of the sub-grain boundaries were chiefly distributed near 1 degrees. As the casting speed increased, some of the local disorientation angles of the grain boundaries exceeded 15 degrees. At casting speeds between 0.83–5.0 mm/s, the wires exhibited unidirectional solidified structures containing low-angle and high-angle tilting grain boundaries.

To improve mechanical properties of porous metals, formation of skin layer on the surface of porous metals is effective. Friction stir incremental forming (FSIF) and incremental hammering (IH) processes were combined to form skin surface layer on a closed-cell type aluminum foam without causing the inside fracture. The cell walls at the surface of the aluminum foam were folded by IH process in the early stage of the process, and then the folded cell walls were stirred and joined by FSIF process. The friction stirred surface layer formed by the combination of IH and FSIF processes was approximately 1.6–4.0 times thicker than that formed by FSIF process. The specific compressive strength of the aluminum foam with the friction stirred surface layer was 1.2–1.6 times higher than that without the friction stirred surface layer due to the formation of the sandwich structure. Influence of the thickness and structure of the skin surface layer on the compressive strength of the aluminum foam with the skin surface layer was discussed.

In order to clarify the effect of a trace sodium at high temperature ductility of 5083 aluminum alloys, elevated temperature tensile tests and microstructure observations were carried out in 5083 alloys containing various amounts of sodium (1–237 ppm). It was shown that sodium content has little effect on grain size and microstructure of 5083 alloys. The author detected sodium element at inclusions on grain boundaries in 5083 alloys containing 237 ppm of sodium using EDS. This suggests that a trace of sodium in 5083 alloys segregate at the inclusions. More than 7 ppm of sodium brought about ductility loss in 5083 alloys at 773 K regardless of grain size in a similar way as reported in 5183 alloys. The author showed that 16 ppm of sodium promote the nucleation of coarse voids during deformation in 5083 alloys. Thus, it is clear that a trace of sodium plays an important role in high temperature ductility loss. On the other hand, 237 ppm of sodium brought about severe embitterment even at room temperature. The result of fracture surface analysis indicates that such a large amount of sodium impurity induces room temperature embrittlement because of significant decohesion of precipitate-matrix interface resulting from sodium segregation.