As 3D printing in metal continues to lead the next industrial revolution, engineers from Australia are taking research one step further in examining improved methods for improving mechanical properties. Choosing a titanium alloy to create samples for experimentation and testing, the authors outlined their findings in the recently published ‘Grain structure control during metal 3D printing by high-intensity ultrasound.’
Samples consisted of 10 mm × 10 mm × 10 mm cubes for microstructural examination and 24 mm × 8 mm × 10 mm (length, width, and height) blocks for tensile testing. Without transforming the alloy at all, the researchers employ an additive manufacturing solidification-control solution to print metallic alloys with equiaxed grain structures, to prevent property anisotropy and the consequent decrease in mechanical performance. In this study, titanium alloy Ti-6Al-4V is used.
Reigning as the ‘benchmark alloy’ of titanium, and the subject of many studies, titanium alloy Ti-6Al-4V is used as a comparison for quality in metal AM processes.
“However, Ti-6Al-4V fabricated by different fusion-based AM processes exhibits a strong columnar grain structure. The columnar prior-β grains in AM-fabricated Ti-6Al-4V feature the strong <001> orientation along the build direction. This gives rise to a β → α transformation texture, which is an important concern for AM qualiﬁcation because of the resulting anisotropy of mechanical properties,” explain the researchers.
“In addition, the coarse columnar prior-β grains may further degrade the strength of Ti-6Al-4V according to the Hall–Petch relationship established for lamellar α–β Ti-6Al-4V21–23 (exceptions can exist).”
While it can be difficult in metal 3D printing to find a strong and stable nucleant alloy, Ti-6Al-4V is exactly that.
Samples were prepared using Ti-6Al-4V both with and without high-intensity ultrasound. The resulting microstructural analysis showed significant differences between the samples, as those without ultrasound displayed columnar prior-β grains of several millimeters in length and ~0.5 mm in width traversing multiple deposited layers (as the researchers anticipated), while the samples used with ultrasound indicated ﬁne (~100 µm), equiaxed prior-β grains. After scanning all the samples with scanning electron microscopy (SEM), the researchers noted a basketweave-like α–β microstructure inside the prior-β grains.
Ultimately, the study showed that the use of ultrasound during the AM process with Ti-6Al-4V allows a fully equiaxed structure to form, resulting in:
- Improvement in microstructural homogeneity
- Significant reduction in the prior-β grain size
- Substantial weakening of the solidification texture
“Assessment of the ultrasonic conditions reveals that the selection of the ultrasound transducer element can be an important practical consideration for structural reﬁnement of large-volume AM-fabricated parts and the use of a magnetostrictive transducer is recommended,” concluded the researchers.
“To assess the generality of our approach, the ultrasonic grain reﬁnement method is successfully applied to the AM of Inconel 625, including the creation of an alternating columnar/equiaxed/ columnar Inconel 625 grain structure along the build height by simply switching on and off the ultrasound during AM. We expect that this technique can be extended to the AM of other metallic materials.”
As metal 3D printing grows in popularity–and industrial users begin to rely more on AM processes, researchers are studying titanium powder as it shows potential for so many applications; for instance, in the fabrication of medical implants in critical surgeries, assistance in bone regeneration, and more.
What do you think of this news? Let us know your thoughts! Join the discussion of this and other 3D printing topics at 3DPrintBoard.com.[Source / Images: ‘Grain structure control during metal 3D printing by high-intensity ultrasound’]
Subscribe to Our Email Newsletter
Stay up-to-date on all the latest news from the 3D printing industry and recieve information and offers from thrid party vendors.
You May Also Like
3D Printing News Unpeeled, Live with Joris Peels Wednesday 17th of August
Today we’re talking about Spectroplast brings a silicone 3D printer on the market, the Pylo 3D printed bike helmet, a study on the effects 3D printing has on global trade,...
3D Printing News Unpeeled, Live with Joris Peels Tuesday 16th of August
Today we’re discussing a revolutionary new open printer for soft materials developed by Cambridge University researchers, Czinger making parts for Aston Martin, Astro America and America Makes BBF? and Craft...
3D Printing News Unpeeled, Live with Joris Peels Monday 15th of August
Today we’re looking at a company that says it is using a more sustainable 3D printing solution. As it’s using EPS foam, we’re a bit skeptical. We’re also looking at...
3D Printing Webinar and Event Roundup: August 14, 2022
This week, you can catch Markforged and Stratasys on the road, and ASTM continues its personnel certificate course. America Makes is celebrating its 10th anniversary and holding MMX, and Nexa3D...