Microstructure investigations of ball milled materials

Area of Science:

• Materials Science
• Nanotechnology
• Physical Metallurgy

Background:

• Nanocrystalline materials exhibit unique properties due to their small grain size.
• Understanding deformation mechanisms and phase formation in immiscible alloys is crucial for developing advanced materials.

Purpose of the Study:

• To investigate the structural and compositional changes in ball-milled copper and Fe-Cu alloys.
• To elucidate the deformation mechanisms in nanocrystalline copper.
• To analyze the formation and characteristics of supersaturated solid solutions in immiscible Fe-Cu systems.

Main Methods:

• High-Resolution Electron Microscopy (HREM)
• Field Emission Gun Transmission Electron Microscopy (FEG TEM)
• Energy Dispersive X-ray Spectroscopy (EDXS)
• Ball Milling (BM)
• Mechanical Alloying (MA)

Main Results:

• Ball milling of copper primarily induces deformation via twinning and shear bands, creating nano-grains with high dislocation density.
• Nanocrystalline copper grain boundaries show a mix of order and disorder, with strained regions and nanovoids.
• Mechanically alloyed Fe16Cu84 forms a supersaturated solid solution, though Fe content is inhomogeneous between grains.
• Thermally decomposed Fe60Cu40 exhibits specific orientation relationships between alpha-Fe and Cu, with significant Cu solubility in alpha-Fe even at high temperatures.

Conclusions:

• Nanocrystalline structure and enhanced diffusion facilitate supersaturated solid solution formation in immiscible systems.
• HREM and EDXS are powerful tools for characterizing subtle structural and compositional changes at the nanoscale.
• The observed high solubility of Cu in alpha-Fe challenges equilibrium predictions for immiscible systems.