Center for Composite Materials - University of Delaware
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Research Summary

Evidence of Mechanical Mixing During Ultrasonic Consolidation Utilizing Focused Ion Beam Milling and Transmission Electron Microscopy

Authors: Jennifer M. Sietins, John W. Gillespie, Jr., and Suresh G. Advani

What is ultrasonic consolidation?

• Ultrasonic Consolidation (UC) is a solid-state processing technique that can be used to weld metal foils together.
• Using a foil-fiber-foil method or prepreg tapes, metal matrix composite (MMC) structures can be fabricated through a layered build-up process.
• Metal foils are placed on top of a stationary anvil and a rotating horn travels the length of the foils.
• Three machine variables:
•• Applied normal force or load
•• Oscillation amplitude
•• Welding speed

Motivation

• Atomistic level microscopy has not been explored for ultrasonically consolidated samples and can provide more information regarding the UC bonding mechanisms.
• Diffusion in particular is a widely debated bonding mechanism due to the short weld times (<1 s) and low temperatures (< 0.5 Tmelting).
• Previous work has shown that x-ray energy dispersive spectroscopy (XEDS) in the Scanning Electron Microscopy (SEM) is not a valid technique to measure the short-scale diffusion during UC due to the interaction volume interference.
• Transmission electron microscopy (TEM) samples should provide more insight for diffusion and other potential bonding mechanisms since the weld zone is of the order of a few microns.

Procedure

Mechanical Mixing Evidence

Conclusions

 Microstructural evidence of mechanical mixing has shown the dispersion of copper-rich fragments, subgrain formation at the interface, and phase transformations
 Intermetallic compounds were identified through TEM XEDS

Acknowledgements

This work is supported by the Army Research Laboratory through the Composite Materials Research program.

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