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 alpha-Al and theta-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. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.