The researchers at HRL Laboratories have successfully developed a technique to 3D print high-strength aluminum alloys such as Al7075 and Al6061. This breakthrough in metallurgy solves ages-old welding problem using nanoparticles. What’s even more exciting is that this technique can also be used with other alloy families such as high-strength steels and nickel-based superalloys.
3D printing, or additive manufacturing, of metals traditionally involves thin layers of alloy powders which are laser heated (or other heat source) until the layers being to melt and solidify. This process is analogous to welding. However, when this method is used on unweldable aluminum alloys the result product suffers from hot cracking— a condition that renders a metal to be pulled apart like a flaky biscuit.
HRL solves this problem by incorporating a nanoparticle functionalization technique. This simply means specially selected nanoparticles decorate the unweldable alloy powder. As this nanoparticle functionalization powder is fed into a 3D printer, lasers are used to fuse each layer and then constructs a three-dimensional object. During melting and solidification, the nanoparticles act as nucleation sites for the desired alloy microstructure, preventing hot cracking and allowing for retention of full alloy strength in the manufactured part.
The HRL team partnered with Citrine Informatics to help them find the correct nanoparticle. In this case zirconium-based nanoparticles were used. "Using Informatics was key," said Yahata who co-led the team with Hunter Martin. "The way metallurgy used to be done was by farming the periodic table for alloying elements and testing mostly with trial and error. The point of using Informatics’ software was to do a selective approach to the nucleation theory we knew to find the materials with the exact properties we needed. Once we told them what to look for, their big data analysis narrowed the field of available materials from hundreds of thousands to a select few. We went from a haystack to a handful of possible needles."
The potential use for this accomplishment is well sought out for, especially in the aerospace and automobile sectors. HRL Laboratories has demonstrated that their new technique for 3D printed unweldable alloys can now lead to faster, cheaper, and more accurate models for production.
For more information, this publication can be found in the September 21st issue of Nature titled, “3D Printing of High-Strength Aluminum Alloys.”