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

We have investigated symmetrical tilt boundaries spontaneously introduced by compressing layer-structured Al-Cu 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.