Al-Si alloy billets with 0, 2, 4, and 6 mass%Cu have been fabricated by the Heat-Insulating-Mold method. The microstructures and high-temperature mechanical properties at 423 K, 523 K, and 623 K have been investigated. Increasing Cu concentration changed the types of constituent particles and increased their area fraction. 0.2% proof stress (σ_0.2) and ultimate tensile strength (σ_UTS) increased with increasing Cu concentration at each temperature. SEM observation showed that precipitates increased with increasing Cu concentration and remained in the matrix below 523 K but dissolved into the Al matrix at 623 K. The former suggested that the precipitates contributed to the strength below 523 K. On the other hand, significant work-hardening was confirmed until 0.2% strain at 623 K, which suggested that the constituent particles contributed to the strength just like particle-reinforced composites. The work-hardening rate and the amount of work-hardening increased with increasing Cu concentration and correlated with the interparticle spacing of the constituent particles. It indicated that decreasing interparticle spacing enhanced constraining matrix deformation, and it led to an increase of σ_0.2 and σ_UTS.

Effect of Si content on the change of earing behavior in deep drawing of 3104 aluminum alloy sheets, under manufacturing processes in which partial annealing and light reduction cold rolling were applied to promote preferential growth of cube-oriented grains related to earing, was investigated. With increasing Si content, the number of fine intermetallic particles acting as Zener pinning force increases, and the critical diameter of recrystallization nuclei of random-oriented grains is increased. As a result, the number of the coarse particles acting as particle stimulated nucleation (PSN) mechanism decreases and the area fraction of Cube-oriented grains increases relatively, where the earing decreases (0, 90° ear increases). The earing is negatively correlated with the area fraction of Cube grains. On the other hand, in the range of Si content of 0.20 to 0.35 mass%, the area fraction of Cube grains and the earing does not change monotonically and shows characteristic behavior. This is considered to be due to the behavior of the number of particles acting as PSN mechanism, determined by the distribution of coarse and fine particles.

Magnesium (Mg) has been paid attention to the viewpoint of weight reduction of structural materials. However, Mg alloys fabricated by the ingot metallurgy process have limited applications as structural materials due to their low mechanical property and low corrosion resistance. In this research, novel Mg-Al alloy was synthesized by the mechanical alloying-spark plasma sintering (MA-SPS) process. Vickers hardness test and X-ray diffraction were carried out to evaluate the effect of Al addition on the properties of the Mg-Al alloys. The hardness improved with increasing amount of Al, in particular when 30 mass% Al was added, the value of hardness was over 200 HV. This improvement was attributable to Mg₁₇Al₁₂ identified by X-ray diffraction. In conclusion, hardness of Mg were improved by the addition of Al via the MA-SPS process.

In this study, the joining of porous aluminum by roll forming was attempted. Two precursors were foamed by heat treatment, and the softened porous aluminum immediately after foaming was roll-formed. It was shown that porous aluminum was simultaneously formed and joined by roll forming while maintaining the porous structure of porous aluminum. In the results of the four-point bending test of the joined samples, pores were observed at the fracture surfaces, indicating that strong joining can be achieved by roll forming. In addition, it was found that strong joining was achieved by optimizing the width of the guide rails during roll forming, in accordance with the size of the precursors.