Ultrasonic effects on gas tungsten arc based wire additive manufacturing of aluminum matrix nanocomposite

Abstract

This study focused on a newly developed ultrasonically assisted (UA) wire arc additive manufacturing (WAAM) process for 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.