The relationship between the grain boundary steps on the specimen surface developed by cyclic bending and fatigue crack generation on the grain boundaries inclined at about 45 degree to the principal stress axis has been discussed for 4N-aluminum wire. The crystal lattice rotation near the grain boundary induced by slip bands in a grain resulted in a strain incompatibility with the neighboring grain. Due to the shear deformation along the grain boundary, the individual grain boundary steps coalesce and form a grain boundary microcrack, resulting in the fatigue crack generation and propagation. The strain incompatibility is developed at the grain boundary between the grain accompanied with crystal rotation over 10 degrees in the vicinity of the boundary and the grain with almost no crystal rotation. Based on the approximation that only the primary slip system is operative, the step height due to the crystal slip deformation is estimated from the lattice rotation near the grain boundary.

Al–10Si–0.3Mg alloy has been additively manufactured on a commercial A5083 aluminum alloy bar through powder bed fusion (PBF) process. Post heat treatment at 813 K for 2 h was carried out after the building. The bonding strength before the heat treatment was higher than the tensile strength of A5083 aluminum alloy. The bonding strength after the heat treatment was higher than the tensile strength of Al–10Si–0.3Mg alloy. Energy-dispersive X-ray spectroscopy reveals the diffusion of Mg atoms from A5083 aluminum alloy to Al–10Si–0.3Mg alloy. Experimental results indicate that the PBF process has a potential to manufacture dissimilar aluminum alloy joints. In addition, Al–10Si–0.3Mg alloy possesses good bonding potential to A5083 aluminum alloy even after post heat treatments.

It is known that the Al–Zn–Mg alloys have the highest specific strength among commercial aluminum alloys because of its excellent age hardenability. Recently, several researchers have reported higher strength in Al–Zn–Mg alloys by high-pressure torsion (HPT), one of the typical methods of severe plastic deformation, than by age-hardening treatment. However, it is difficult to apply HPT processing for manufacturing practical parts. In addition, high-strength Al–Zn–Mg alloys often show hydrogen embrittlement in humid environment. In this study, we have investigated the effect of cold rolling on the strength and resistance to hydrogen embrittlement in an Al–8%Zn–2%Mg–2%Cu–0.15%Zr alloy by means of tensile test in the environments of dry nitrogen gas and humid air with 90% relative humidity at several initial strain rates. The specimen cold-rolled by 65% shows higher tensile strength than the specimen heat-treated to peak-aged condition. It is noted that the cold-rolled specimen is not susceptible to hydrogen embrittlement.