Interfacial excess of solutes across phase boundaries using atom probe microscopy

Area of Science:

• Materials Science
• Analytical Chemistry
• Physical Metallurgy

Background:

• Atom probe microscopy offers quasi-atomic resolution for elemental mapping at material interfaces.
• Understanding solute segregation at grain boundaries is crucial for material properties.
• Complex alloys like Ni-based superalloys present challenges due to multiple solutes and precipitates near grain boundaries.

Purpose of the Study:

• To develop a quantitative methodological framework for characterizing phase boundaries near grain boundaries using atom probe microscopy.
• To address the obscuring effects of abrupt solute solubility changes on interfacial excess measurements.
• To enable precise compositional control in complex engineering alloys.

Main Methods:

• Utilizing atom probe microscopy for three-dimensional elemental mapping.
• Analyzing detailed mass spectra of MC, M23C6, and M6C carbides for compositional accuracy.
• Employing proximity histograms and concentration difference profiles to locate interfaces.
• Introducing quantitative 'interface plots' for intuitive data interpretation.

Main Results:

• A reliable method for directly calculating interfacial excess across phase boundaries was established.
• The framework successfully characterized phase boundaries between various phases (γ-matrix, γ' precipitates, carbides).
• The study demonstrated accurate quantification of local composition near grain boundaries in complex microstructures.

Conclusions:

• The developed framework provides advanced access to local composition near grain boundaries in complex alloys.
• This methodology is applicable to other engineering alloys and materials with functional properties.
• The findings facilitate improved material development and processing through precise compositional understanding.