Stress-induced symmetrical tilt boundaries in layer-structured Al-Cu eutectic alloys

We have investigated symmetrical tilt boundaries spontaneously introduced by compressing layer-structured AlCu eutectic alloys, based on scanning electron microscopy (SEM), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM) and crystal plasticity (CP) analysis. SEM observations show sine-wave-like bending of a layered structure consisting of soft Al and hard Al2Cu phases and sharp symmetric tilt boundaries appeared only in the Al layers at the corner of the waves. TEM/STEM observations revealed that the tilt-boundaries consist of a single variant of dislocations, the feature of which is similar to the kink boundary that normally occurs in anisotropic crystals such as hexagonal close-packed. CP analysis indicated that differences in plastic deformation capacity between the Al and Al2Cu layers cause selective activation of slip systems in soft Al layers, which induces rotational deformation accompanied by the spontaneous formation of kink boundaries.