Local structures of mechanically alloyed Fe100-xCux solid solutions studied by X-ray absorption fine structure

Area of Science:

• Materials Science
• Metallurgy
• Solid-State Physics

Background:

• Immiscible Fe-Cu alloys present unique structural properties.
• Mechanical alloying is a method to produce supersaturated solid solutions.
• Understanding local atomic structures is crucial for alloy performance.

Purpose of the Study:

• Investigate the local structures of immiscible Fe(100-x)Cu(x) alloys produced by mechanical alloying.
• Analyze structural transitions and homogeneity in Fe-Cu supersaturated solid solutions.
• Explore the influence of ball milling on the crystal structure of Fe-Cu alloys.

Main Methods:

• X-ray Absorption Fine Structure (XAFS) spectroscopy was employed.
• Mechanical alloying was used to produce Fe(100-x)Cu(x) alloys with varying compositions (x = 0-100).
• Analysis of Debye-Waller factors to assess atomic vibrations and local disorder.

Main Results:

• Fe atoms in Fe(100-x)Cu(x) (x ≥ 40) transitioned from bcc to fcc structures, while Cu atoms retained their coordination.
• Cu atoms in Fe80Cu20 and Fe90Cu10 alloys showed an fcc to bcc structural transition.
• The Debye-Waller factor (sigma) for the fcc Fe-Cu phase was higher than for the bcc phase, indicating greater disorder.

Conclusions:

• Mechanically alloyed Fe-Cu supersaturated solid solutions are not homogeneous, exhibiting Fe-rich and Cu-rich regions.
• Ball milling induces significant interdiffusion and structural transitions (bcc-to-fcc and fcc-to-bcc) in Fe-Cu alloys.
• The observed structural changes are attributed to mechanical alloying-induced interdiffusion and phase transitions.