Theory of solute clustering in materials for atom probe

Abstract

Pseudo-binary solute clustering in crystals was modelled analytically using expressions for the site-occupation probabilities that depend on solute concentration, crystallography and nearest-neighbour short-range order. Up to a cluster-size of 10 solute atoms, theoretical random and non-random cluster-size distributions were calculated for diamond (Si), simple (Mn), body centred (Fe) and face centred (Al) cubic lattices and the hexagonal close-packed (Mg) lattice. These calculations were then used to generate simulations of atom probe data, by stochastically removing atoms to simulate the effect of detector efficiency. These simulations may be used to determine self-consistent clustering algorithm parameters, measure short range order parameters and recover the effect of detector efficiency on the observed frequency distributions.

Keywords:

• atomic clustering
• atom probe
• microscopy
• tomography
• atomistic simulation
• short range order

Acknowledgements

Funding from the Australian Research Council is gratefully acknowledged. The authors are grateful for scientific and technical input and support from the Australian Microscopy & Microanalysis Research Facility (AMMRF) node at the University of Sydney.