Combinatorial Study of Gradient Ag-Al Thin Films: Microstructure, Phase Formation, Mechanical and Electrical...

Area of Science:

• Materials Science
• Surface Engineering
• Tribology

Background:

• Pure silver (Ag) exhibits favorable electrical conductivity but suffers from high friction and adhesive wear.
• Developing Ag-based alloys with improved tribological properties while maintaining electrical performance is crucial for advanced applications.

Purpose of the Study:

• To investigate the mechanical, tribological, and electrical properties of Ag-Al thin films across a wide composition range.
• To identify Ag-Al compositions with enhanced performance for sliding electrical contact applications.

Main Methods:

• Combinatorial magnetron sputtering was used to deposit Ag-Al thin films with continuous composition gradients.
• Characterization involved X-ray diffraction (XRD), electron microscopy (SEM, TEM), spectroscopy (EDX, XPS), nanoindentation, and electrical resistance measurements.

Main Results:

• Ag-Al films transitioned from a face-centered cubic (fcc) phase at low aluminum (Al) content to a hexagonal close-packed (hcp) solid solution phase at higher Al concentrations.
• The hcp Ag-Al phase exhibited significantly reduced friction coefficients (approx. 15% of fcc) and adhesive wear compared to pure Ag.
• Contact resistance increased by only ~50% over pure Ag in the low-friction hcp region (19-27 atom % Al).

Conclusions:

• A hexagonal solid solution Ag-Al alloy offers a promising alternative to pure Ag for sliding electrical contacts due to its superior tribological performance.
• These Ag-Al alloys demonstrate potential for replacing pure Ag in specific electromechanical applications requiring both conductivity and wear resistance.