Processing-dependent Chemical Ordering in a Metallic Alloy Characterized via Non-destructive Bragg Coherent Diffraction Imaging

TL;DR

This study uses non-destructive Bragg coherent diffraction imaging to analyze how heat treatments affect chemical ordering and strain distribution in Cu3Au nanocrystals, aiding alloy design.

Contribution

It demonstrates a novel application of Bragg coherent diffraction imaging to correlate chemical ordering with strain distribution in nanocrystals.

Findings

Increased chemical ordering correlates with reduced strain and narrower strain distributions.

Spatial correlations exist between scattering amplitude and lattice strains.

Heat treatments influence chemical ordering and strain characteristics.

Abstract

Of current importance for alloy design is controlling chemical ordering through processing routes to optimize an alloy's mechanical properties for a desired application. However, characterization of chemical ordering remains an ongoing challenge, particularly when nondestructive characterization is needed. In this study, Bragg coherent diffraction imaging is used to reconstruct morphology and lattice displacement in model Cu$_3$Au nanocrystals that have undergone different heat treatments to produce variation in chemical ordering. The magnitudes and distributions of the scattering amplitudes (proportional to electron density) and lattice strains within these crystals are then analyzed to correlate them to the expected amount of chemical ordering present. Nanocrystals with increased amounts of ordering are found to generally have less extreme strains present and reduced strain distribution widths. In addition, statistical correlations are found between the spatial arrangement of scattering amplitude and lattice strains.