Deformation behavior of nanoscale Al-Al2Cu eutectics studied by in situ micropillar compression

Deformation behavior of nanoscale laser processed Al-Al2Cu eutectics at room temperature is characterized through in situ micro-pillar compression testing in a scanning transmission microscope. Interlamellar spacing of Al-Al2Cu eutectics varies from hundreds of nanometers to 20 nm. Three different sizes of micro-pillars are fabricated in order to study the deformation behaviors of single colony and multiple colonies, corresponding to the single crystal and polycrystal respectively. For single colonies, lamellar orientations parallel, normal or inclined to the loading direction were tested. The main findings are: 1) the plasticity mechanisms strongly depend on loading orientation: buckling and kinking in the parallel-loaded eutectics, planar sliding along Al-Al2Cu lamellar interfaces in the incline-loaded eutectics and localized shearing in the normal-loaded eutectics. 2) the incline-loaded eutectics exhibits the lowest compression flow strength, and the normal-loaded eutectics has the highest compression flow strength. 3) with decreasing inter-lamellar spacing, the strength increases and plasticity is uniformly distributed, as opposed to shear localization. Highest compressive plasticity is observed in polycrystalline eutectics with an ensemble of lamellar orientations with-20 nm average spacing: 17.9% at flow stress of 1.63 GPa, and degenerate, bimodal morphology: 11.1% at flow stress of 1.36 GPa.

Automated summary

The study revealed that the deformation behavior of nanoscale laser processed Al-Al2Cu eutectics is greatly influenced by the loading orientation, with different mechanisms observed for parallel, inclined, and normal loading. Decreasing inter-lamellar spacing led to increased strength and more uniform plasticity distribution, with the highest compressive plasticity observed in polycrystalline eutectics with an average spacing of 20 nm.