Time evolution of morphology in mechanically alloyed Fe-Cu

Area of Science:

• Materials Science
• Metallurgy
• Nanotechnology

Background:

• Iron-Copper (Fe-Cu) alloys are model systems for studying enhanced solubility.
• Fe-Cu exhibits limited miscibility and a large positive heat of mixing.
• Ball milling is a common fabrication method for alloy powders.

Purpose of the Study:

• To investigate the enforced nonequilibrium enhanced solubility in ball-milled Fe-Cu powders.
• To analyze atomic mixing, impurity distribution, and structural evolution during milling.
• To correlate morphological changes with chemical mixing at various length scales.

Main Methods:

• Atom Probe Tomography (APT) for atomic-scale analysis.
• Transmission Electron Microscopy (TEM) for site-specific structural analysis.
• Focused Ion Beam (FIB) for TEM lamellae preparation.
• X-ray Diffraction (XRD) for grain size determination.

Main Results:

• Striking morphological differences observed based on Fe-Cu mixing ratios.
• Atomic mixing of Fe and Cu evaluated, along with impurity distribution.
• Correlation established between structural evolution and chemical mixing.
• Nanoscale homogeneity achieved, extending the miscibility region beyond equilibrium predictions.
• Ball milling texture related to classical rolling texture of iron.
• Nanocrystalline structures confirmed by XRD and TEM.

Conclusions:

• Ball milling enables significant enhancement of Fe-Cu miscibility, creating a nanocrystalline structure.
• Combined APT and TEM provide unprecedented insight into powder particle evolution.
• Site-specific analysis reveals distinct surface and interior morphologies.
• The study demonstrates the potential for achieving full nanoscale homogeneity in Fe-Cu alloys.