Structural refinement and nanomechanical response of laser remelted Al-Al2Cu lamellar eutectic

Laser remelting was employed to refine the interlamellar spacing (λ) to approximately 30nm on an arc-cast Al-32.7wt%Cu eutectic. λ scaled with A ′(h)-°0.25 where h is the distance from the trace bottom, and A ′ is a factor dependent on laser processing conditions. A′ increased with the laser power (at a constant spot diameter) but decreased with the spot diameter (at a constant laser power). The nanoindentation measured hardness increased up to 4.68GPa with decreasing interlamellar spacing, following the Hall-Petch relation. The as-cast eutectics showed microcracks around indents, while cracking was suppressed in the laser remelted nanoscale eutectics. A dislocation theory based mechanism is proposed for the enhanced plastic co-deformation of fine scale laser-remelted Al-Al2Cu eutectics.