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Ultrasonic effects on GTA-based wire additive manufacturing ManufacturingX Lab

A newly developed ultrasonically assisted (UA) wire arc additive manufacturing (WAAM) process was applied for application of metal matrix nanocomposite of AA7075 with TiB2 nanoparticles. The ultrasonic probe was directly dipped into the local molten pool and traveled behind the arc during deposition. Comprehensive experimental studies were performed and the UA-WAAM sample showed superiorities over conventional WAAM ones in multiple perspectives including a lower number of porosities, refined solidification structure, and less agglomerated nanoparticle distribution under the same deposition parameters. These improved microstructure features led to enhanced mechanical properties of the UA-WAAM samples, as reflected in the tensile tests and hardness measurement results. The benefits of nanoparticles in the formation of equiaxed grain structures and strength contribution was further leveraged by UA based on their better dispersion. The ultrasonic effects on WAAM process can be mainly attributed to the two nonlinear physical phenomena: acoustic cavitation and streaming induced by power ultrasound in molten metal. 

UA effect on microstructure

UA effect on microstructure 2 Xun Liu Ohio State Welding Engineering

Equiaxed grain structure with random orientation was observed in both no-UA and UA builds. White regions in Kernel Average Misorientation (KAM) indicated high strain spots associated with lattice distortion. High strain level was found in UA build compared to no-UA one. It was also observed that grain growth was retarded in UA build, as reflected in the refined grain structure in UA build.


UA effect on nanoparticle dispersion

UA effect on nanoparticle dispersion

Agglomerations of nanoparticles were only discovered at grain boundaries in no-UA sample, whereas UA sample showed a fashion of nanoparticles decorated on the secondary phases at grain boundaries, indicating a better dispersion of nanoparticles with the assistance of ultrasound. 


UA effect on mechanical behavior

UA effect on mechanical behavior

UA build also showed a more homogeneous and advanced hardness distribution, associated with refined microstructure, higher level of strain, and better dispersion of nanoparticles contributed by UA during the process. Accordingly, better tensile strength was also achieved with UA. 

This project is sponsored by National Science Foundation.