In this study, the method of high-pressure sliding (HPS) was applied for grain refinement of an A2024 alloy. Samples in a rod shape were used in this HPS process. To achieve homogeneous grain refinement throughout the cross section of the rods, the samples were rotated around the longitudinal axis of the rod every after HPS processing. Microstructural observations revealed that the grain size was refined to 140 nm. Tensile tests showed that the samples exhibited superplasticity with a maximum elongation of 480% at 623 K and 1.0×10-3s-1 and with a strain rate sensitivity of 0.36.
Computer experiments of irradiated Al–Si alloys were performed to clarify the mechanism of radiation enhanced segregation. The atomic configurations of pure Al, Al–5 at%Si and Al–10 at%Si with amorphous structure after the irradiation of high energy beam were calculated by the molecular dynamics method. We estimated the threshold energies to create voids in pure Al, Al–5 at%Si and Al–10 at%Si as 0.23, 0.25 and 0.25 keV/nm, respectively. This fact means that addition of Si to Al enhances strength against void formation by beam irradiation. We also confirmed that addition of Si to Al gave strong effect on radiation enhanced segregation. The degree of enhancement depended on the degree of dispersion of Si atoms in Al matrix because the Si atoms enhances clustering of the Al atoms surrounding them.
The effects of the aging conditions on the serrated flow in Al–Mg (–Zn) alloys were investigated, focusing on the precipitation states. Al–6%Mg and Al–6%Mg–3%Zn alloys were naturally and artificially aged after solution treated and quenched. The serrated flow was examined by tensile test. As for the Al–6%Mg–3%Zn alloy, the naturally aged specimens show the increase in the critical strain for serrated flow. The Zn–Mg clusters are formed during natural aging. Furthermore, the increase in the number density and the size of these clusters corresponds to the increase in the critical strain, which reveals that the formation of these coherent clusters is one of the dominant factors for delaying the onset of serrated flow. On the other hand, as for the artificially aged specimens in the under-aged conditions, the transformation of the clusters to the incoherent meta-stable precipitates brings about the decrease in the critical strain. Furthermore, the increase in the volume fraction of these precipitates in the over-aged conditions reduce the stress amplitude of serrated flow, which is brought about by the decrease in the solute Mg content.
The study of texture control in aluminum alloys is thriving. For example, Cube orientation has been found to be effective for improving bending workability of Al–Mg–Si alloys. In this study, commercial-purity aluminum (A1050-H18) and Al–Mg alloy (A5052-O) plates were irradiated by a laser beam, measured using a SEM apparatus and then bending tested. In A1050-H18 subjected to slower laser irradiation, Cube orientation was developed as a result of recrystallization due to the higher achieving temperatures than 680 K. In A5052-O, on the other hand, Cube orientation was developed in all the investigated irradiation conditions. From IPF maps of both of specimens, preferential orientation was found to be accumulated into the ‹001› direction, resulting in the softening and thus enhanced bending workability by the laser irradiation, while ‹101› direction containing Goss orientation is reduced. The area fraction of Cube orientation did not affect the bending workability, suggesting that softening has a synergistic effect with texture control.