Researchers from RMIT University’s School of Engineering have used ultrasound vibrations to shake metal alloy grains into a tighter formation during 3D printing. This creates stronger and more stable structures for industrial uses. The high-frequency soundwaves from an ultrasound can have an impact on the inner microstructure of 3D printed alloys, making the final product stronger and more consistent.

3D printed titanium alloys under an electron microscope: sample on the left with large, elongated crystals was printed conventionally, while sample on the right with finer, shorter crystals was printed sitting on a ultrasonic generator. Source: RMIT University

The microscopic structure of 3D printed alloys typically looks like large and elongated crystals. This leads to a higher chance of the product cracking during printing and results in lower overall mechanical performance. Because of this, 3D printed parts are not optimal for engineering uses at this time.

The 3D printed alloys applied with ultrasound had a very fine structure and were formed equally in all directions throughout the whole part. The new parts had a 12% improvement in tensile strength and yield stress, compared to conventional 3D printed parts. Switching the ultrasound on and off during printing showed the team how specific parts can be made with different structures also known as functional grading.

Researchers demonstrated their new approach with two major commercial-grade alloys. The first was Ti-AI-4V, a titanium alloy that is commonly used for aircraft parts and biochemical implants. The second was Inconel625, a nickel-based superalloy typically used in marine and petroleum industries.

The team hopes their results will spark interest in specially designed ultrasound devices for 3D printing. They also believe their findings could inspire new kinds of 3D printing. The method can also be applied to other commercial alloys and scaled up for industrial production.

A paper on the new method was published in Nature Communications.