Plasticity of laser-processed nanoscale Al–Al₂Cu eutectic alloy

Deformation behavior of as-cast and laser re-melted Al–Al₂Cu eutectic alloys subjected to room temperature rolling was investigated by transmission electron microscopy. For as-cast alloys, with inter-lamellar spacing of a few micrometers, Al₂Cu layers exhibit brittle behavior but plastic co-deformation was observed in rolled, laser processed nanoscale alloys. The nanoscale Al₂Cu lamellae, constrained by nanoscale Al, deform via defects not previously reported in monolithic Al₂Cu intermetallic: localized shear on {011}_Al2Cu planes and shear-induced faults on {121}_Al2Cu planes. Based on crystallographic analysis of slip continuity across the interface, the unexpected plasticity mechanisms are ascribed to the slip continuity across interface between α-Al and θ-Al₂Cu layers associated with the orientation relationship in Al–Al₂Cu eutectics. The difference in shear mechanisms on the two planes is attributed to low energy faulted structures associated with shear on {011}_Al2Cu and {121}_Al2Cu planes, as examined by first-principles density functional theory calculations. These findings demonstrated that nanoscale microstructures promote plastic co-deformation in metallic composites with soft and hard phases.