Engineers 3-D print high-strength aluminum, solve ages-old welding problem using nanoparticles

September 20, 2017, HRL Laboratories
With this exciting new technique, HRL stands at the forefront of a new chapter in additive manufacturing of metals for research, industry, and defense. Credit: M. Durant HRL Laboratories

HRL Laboratories has made a breakthrough in metallurgy with the announcement that researchers at the famous facility have developed a technique for successfully 3D printing high-strength aluminum alloys—including types Al7075 and Al6061—that opens the door to additive manufacturing of engineering-relevant alloys. These alloys are very desirable for aircraft and automobile parts and have been among thousands that were not amenable to additive manufacturing—3D printing—a difficulty that has been solved by the HRL researchers. An added benefit is that their method can be applied to additional alloy families such as high-strength steels and nickel-based superalloys difficult to process currently in additive manufacturing.

"We're using a 70-year-old nucleation theory to solve a 100-year-old problem with a 21st century machine," said Hunter Martin, who co-led the team with Brennan Yahata. Both are engineers in the HRL's Sensors and Materials Laboratory and PhD students at University of California, Santa Barbara studying with Professor Tresa Pollock, a co-author on the study. Their paper 3D printing of high-strength aluminum was published in the September 21, 2017 issue of Nature.

Additive manufacturing of metals typically begins with alloy powders that are applied in thin layers and heated with a laser or other direct heat source to melt and solidify the layers. Normally, if high-strength unweldable aluminum alloys such as Al7075 or AL6061 are used, the resulting parts suffer severe hot cracking—a condition that renders a metal part able to be pulled apart like a flaky biscuit.

HRL's nanoparticle functionalization technique solves this problem by decorating high-strength unweldable alloy powders with specially selected . The nanoparticle-functionalized powder is fed into a 3D printer, which layers the powder and laser-fuses each layer to construct 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 nanoparticle-functionalized powder is fed into a 3-D printer, which layers the powder and laser-fuses each layer to construct a three-dimensional object. Credit: B. Ferguson - HRL Laboratories

Because melting and solidification in additive manufacturing is analogous to welding, HRL's nanoparticle functionalization can also be used to make unweldable alloys weldable. This technique is also scalable and employs low cost materials. Conventional alloy powders and nanoparticles produce printer feedstock with nanoparticles distributed uniformly on the surface of the powder grains.

"Our first goal was figuring out how to eliminate the hot cracking altogether. We sought to control microstructure and the solution should be something that naturally happens with the way this material solidifies," Martin said.

To find the correct nanoparticles, in this case zirconium-based nanoparticles, the HRL team enlisted Citrine Informatics to help them sort through the myriad possible particles to find the one with the properties they needed.

"Using informatics was key," said Yahata. "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."

With this exciting new technique, HRL stands at the forefront of a new chapter in of metals for research, industry, and defense.

Explore further: Nanoparticles improve the strength of metallic alloys

More information: 3D printing of high-strength aluminium alloys, Nature (2017).

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5 / 5 (2) Sep 20, 2017
Now here is a technology that can utterly transform our industries and economy. When this technology matures and becomes cheap enough for home ownership, can you imagine how that will change things? You will still need factories to build big stuff like cars but smaller goods.... that could all be done at home and it would be a boon to a host of hobbyists.
5 / 5 (1) Sep 20, 2017
Now we can print engine blocks, and tomorrow:- complex 3D structures of metallic conductors or engine components, ceramic insulators and polymer flexible sections. Satellites and space vessels will be made without the thousands of hours of labourers acting like robots, following instructions, to assemble 100,000 pieces in to the one configuration that will work.
not rated yet Sep 20, 2017
I hope that the nanoparticles are not 10x more expensive than the material being fused.
not rated yet Sep 20, 2017
cgsperling hit the 3-D printed nail on the head. The only thing preventing 3-D printing from disrupting industrial scale manufacturing - is the economics. 3-D is economical for one off molds, tooling and or high value items no longer being manufactured. However, and especially in metallurgy 3-D printing energy budgets are orders of magnitude higher than traditional processes currently being used. That isn't going to change.
not rated yet Sep 21, 2017
The initial costs will be high but that means it first gets used (and developed) in formula 1 cars and surgical prosthetics and aerospace.
Eventually it will be as ubiquitous in 3D as the printed circuit board is in 2D; which enabled the electronics revolution.
not rated yet Sep 21, 2017
Now we can print engine blocks

Question is, why would you? If you're making a million, casting is cheaper and faster.

as the printed circuit board is in 2D

You do know they aren't actually printed in the same sense, like there exists a printer that just lays tracks on a board? (well, there is, but again, it's slower and less economical)
not rated yet Sep 21, 2017
A 3D printed "engine block" would have optimised integrated lubrication and cooling and weight saving meshes not possible in a casting.
The 2D circuit board by replacing an impractically large plate full of spaghetti wiring, is a good analogy for the structures and systems which a multi-material 3D matrix would replace; by enabling structural and functional parts of a system and interconnects to be integrated in a single form. Power distributions and high frequency cavities and optical bus interconnects and thermal management and weight reduction could be integrated in a repeatable manner into whatever aerodynamic or ergonomic or functional shape you need.
not rated yet Sep 22, 2017
A 3D printed "engine block" would have optimised integrated lubrication and cooling and weight saving meshes not possible in a casting.

That's a question of whether the gains are worth the cost. Is the engine going to be that much better, and do you need it to be?

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