Dynamical scattering image simulations for two-phase γ-γ' microstructures: A theoretical model.

Area of Science:

• Materials Science
• Crystallography
• Computational Materials Science

Background:

• The Darwin-Howie-Whelan (DHW) equations are fundamental for simulating electron diffraction in crystalline materials.
• Modeling coherent precipitates requires extensions to account for complex interfacial structures and strain fields.
• Understanding precipitate behavior is crucial for designing advanced alloys with tailored properties.

Purpose of the Study:

• To extend the DHW equations for coherent L1$_{2}$ precipitates in an FCC matrix.
• To develop a fast and accurate image simulation scheme using pre-computed scattering matrices.
• To investigate the dynamical scattering of electrons in synthetic Ni-Al microstructures.

Main Methods:

• Extension of the Darwin-Howie-Whelan (DHW) equations to include L1$_{2}$ precipitates and arbitrary lattice defects.
• Development of an approximate scheme for rapid image simulations utilizing pre-computed scattering matrices.
• Generation of synthetic microstructures using phase field simulations for Ni-Al alloys.

Main Results:

• The extended DHW equations successfully model coherent L1$_{2}$ precipitates and their associated displacement fields.
• The approximate simulation scheme provides fast and accurate diffraction pattern and image simulations.
• Dynamical scattering simulations show that precipitate superlattice beams propagate but are decoupled from matrix fundamental waves.

Conclusions:

• The extended DHW equations provide a powerful tool for analyzing electron diffraction in materials with coherent precipitates.
• The developed simulation method enables efficient and accurate prediction of microstructural images and diffraction patterns.
• The findings offer insights into the wave propagation characteristics at precipitate-matrix interfaces, crucial for materials characterization.