Nanoscale mapping of residual stresses in Al 2024 alloys using correlative and multimodal scanning transmission electron microscopy

Mohamed E Daoud; Inas Taha; Mohamed Helal; H Kamoutsi; G N Haidemenopoulos; Kamran A Khan; Dalaver H Anjum

doi:10.1016/j.heliyon.2024.e30280

Nanoscale mapping of residual stresses in Al 2024 alloys using correlative and multimodal scanning transmission electron microscopy

Heliyon. 2024 Apr 26;10(9):e30280. doi: 10.1016/j.heliyon.2024.e30280. eCollection 2024 May 15.

Authors

Mohamed E Daoud¹, Inas Taha¹, Mohamed Helal², H Kamoutsi³, G N Haidemenopoulos³, Kamran A Khan⁴, Dalaver H Anjum¹

Affiliations

¹ Department of Physics, Khalifa University, P.O. Box 127788, Abu Dhabi, United Arab Emirates.
² Core Research Laboratories, Khalifa University, P.O. Box 127788, Abu Dhabi, United Arab Emirates.
³ Laboratory of Materials, Department of Mechanical Engineering, University of Thessaly, Pedion Areos, 38334, Volos, Greece.
⁴ Aerospace Engineering Department, Khalifa University, P.O. Box 127788, Abu Dhabi, United Arab Emirates.

Abstract

A methodology for the mapping of residual stresses in metal alloys has been developed by analyzing an isotropic and homogeneous Al2024 alloy with scanning transmission electron microscopy (STEM), combined with diffraction (4DSTEM) and electron energy loss spectroscopy (STEM-EELS) techniques of TEM. The investigations on the alloy's microstructure and elemental distributions were also carried out with conventional dark-field STEM (DFSTEM) and X-ray energy dispersive (EDS) techniques, respectively. Using the STEM-EELS technique, the Young's modulus (Y_M) is mapped in the (001) plane of the Al alloy in the same regions where the residual strain maps are generated in [ $\overline{1}$ 00] and [010] directions by using 4DSTEM technique. The $Y_{M}$ vs. residual strain plot for the Al 2024 alloy revealed that the value of $Y_{M}$ decreased by about $\sim$ 7 % after the tensile residual strain reached 0.02 %. Whereas such a decrease in $Y_{M}$ happens after the compressively residual strain reaches -0.015 %. The residual stress maps were also obtained in accordance with the Hooke's law i.e., by multiplying $Y_{M}$ map with the corresponding residual strain maps.

Keywords: Al 2024 alloy; Electron energy loss spectroscopy (EELS); Four-dimensional transmission electron microscopy (4D STEM); Residual stresses; Scanning transmission electron microscopy (STEM); Young's modulus.