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Synthesis and Characterization of Ultrasonically Atomized Al-Based Alloy Powders for Tunable Thermal Reactivity

Chetan Singh, Ava Goglia, Peter Mastracco, Michael Flickinger, Laszlo J. Kecskes, Paulette Clancy, Timothy P. Weihs

TL;DR

Reactive aluminum powders address high reactivity needs but raise safety and handling concerns at nanoscale. This work uses ultrasonic atomization to create micron-sized Al-based powders (pure Al and Al–Cu, Al–Si, Al–Mg) and comprehensively characterizes their microstructure, phase content, and oxidation behavior to enable tunable ignition. Mg-rich alloys exhibit Mg-dominated oxidation with large mass gains, while Cu- and Si-containing alloys preserve near-protective oxide behavior; alloy-driven near-surface phases modulate oxidation onset and exotherms. The study provides a manufacturing-forward framework linking composition, microstructure, and reactivity, offering tunable, flowable powders for additive manufacturing and energetic/joining applications.

Abstract

Reactive aluminum (Al) alloy powders are promising for advanced manufacturing, joining, and energetic applications, yet scalable routes that couple controlled reactivity with safe handling remain limited. While nanoscale Al powders ignite readily, their agglomeration, handling, and safety limit broad deployment. Here, we manufacture micron-sized Al-based powders produced by ultrasonic atomization (UA), targeting a balance of enhanced reactivity and process robustness. Binary systems (AlCu, AlSi, AlMg) and pure Al were synthesized, and their morphology, phases present, thermal stability, and oxidation behavior were characterized using XRD, SEM, and DTA/TGA in an Ar/O2 environment. We show that alloy selection and UA-controlled microstructure can modify the native Al2O3 passivation, alter oxidation pathways, and shift thermal onsets/exotherms. The results establish a manufacturing-forward framework for designing micron-sized powders with tunable ignition/oxidation behavior.

Synthesis and Characterization of Ultrasonically Atomized Al-Based Alloy Powders for Tunable Thermal Reactivity

TL;DR

Reactive aluminum powders address high reactivity needs but raise safety and handling concerns at nanoscale. This work uses ultrasonic atomization to create micron-sized Al-based powders (pure Al and Al–Cu, Al–Si, Al–Mg) and comprehensively characterizes their microstructure, phase content, and oxidation behavior to enable tunable ignition. Mg-rich alloys exhibit Mg-dominated oxidation with large mass gains, while Cu- and Si-containing alloys preserve near-protective oxide behavior; alloy-driven near-surface phases modulate oxidation onset and exotherms. The study provides a manufacturing-forward framework linking composition, microstructure, and reactivity, offering tunable, flowable powders for additive manufacturing and energetic/joining applications.

Abstract

Reactive aluminum (Al) alloy powders are promising for advanced manufacturing, joining, and energetic applications, yet scalable routes that couple controlled reactivity with safe handling remain limited. While nanoscale Al powders ignite readily, their agglomeration, handling, and safety limit broad deployment. Here, we manufacture micron-sized Al-based powders produced by ultrasonic atomization (UA), targeting a balance of enhanced reactivity and process robustness. Binary systems (AlCu, AlSi, AlMg) and pure Al were synthesized, and their morphology, phases present, thermal stability, and oxidation behavior were characterized using XRD, SEM, and DTA/TGA in an Ar/O2 environment. We show that alloy selection and UA-controlled microstructure can modify the native Al2O3 passivation, alter oxidation pathways, and shift thermal onsets/exotherms. The results establish a manufacturing-forward framework for designing micron-sized powders with tunable ignition/oxidation behavior.

Paper Structure

This paper contains 15 sections, 5 figures, 1 table.

Table of Contents

  1. Introduction
  2. Materials and Methods
  3. Ultrasonic atomization
  4. Particle size analysis
  5. X-ray Diffraction (XRD)
  6. SEM/EDS and Phase Analysis
  7. Thermal Analysis
  8. Results and Discussion
  9. Particle size distributions, and implications for atomization
  10. Phase constitution and solidification pathways
  11. Particle morphology and near-surface features
  12. Thermal stability and oxidation behavior
  13. Implications for reactive applications and manufacturing quality control
  14. Future work
  15. Conclusion

Figures (5)

  • Figure 1: (a) Volume-based PSDs for as-atomized Al-alloy powders; (b) cumulative distribution functions (CDFs) of the volume-based PSDs.
  • Figure 2: XRD patterns of as-atomized Al-alloy powders. Phase identification includes fcc-Al for all powders; Si (diamond cubic) in Al--Si; $\theta$-Al2Cu in Al--Cu; and $\beta$-Al3Mg2 in Al--Mg.
  • Figure 3: Representative SEM images of as-atomized powders: (a) Pure Al; (b) Al--33 wt.% Cu; (b1) higher-magnification lamellae; (c) Al--13 wt.% Si; (d) Al--33 wt.% Mg; (d1) higher magnification indicating likely $\beta$-Al3Mg2/oxide contrast.
  • Figure 4: TGA curves in Ar/O2 (80/20 vol.%): (a) full-scale comparison; (b) zoom on low-gain alloys.
  • Figure 5: DSC heat-flow curves for the 32--53 µm fraction under Ar/O2 (80/20 vol.%).