Elastic strain mapping of plastically deformed materials by TEM

Area of Science:

• Materials Science
• Solid Mechanics
• Electron Microscopy

Background:

• Standard strain measurement methods struggle with orientation gradients in plastically deformed materials.
• Accurate mapping of elastic strain fields is crucial for understanding material deformation behavior.
• Transmission Electron Microscopy (TEM) offers high-resolution imaging but requires specialized methods for quantitative strain analysis.

Purpose of the Study:

• To develop and present a novel method for mapping elastic strains in plastically deformed materials using TEM.
• To address the challenge of orientation gradients in strain analysis.
• To enable detailed characterization of strain fields around microstructural features like dislocations.

Main Methods:

• Coupling orientation and strain maps from scanning precession electron diffraction (SPED) datasets.
• Accounting for orientation gradients by rotating the coordinate system based on measured disorientation.
• Calculating elastic strains in the rotated coordinate system, currently handling azimuthal rotations.
• Application to a plastically deformed Cr2AlC monocrystal subjected to nanomechanical testing.

Main Results:

• The developed method successfully maps elastic strain fields in a plastically deformed Cr2AlC sample.
• Strain fields around dislocations, including pile-ups and walls, are consistent with theoretical predictions.
• Distinct differences in strain fields between dislocation pile-ups and walls were observed.
• The strain maps facilitated the identification of the Burgers vector orientation and estimation of dislocation source positions.

Conclusions:

• The presented method provides a robust approach for elastic strain mapping in materials with orientation gradients.
• This technique enhances the understanding of dislocation behavior and plastic deformation mechanisms.
• Future applications include detailed studies of complex deformed microstructures and materials.