New technique enables 3D printing with high-strength aluminum alloys

HRL's nanoparticle functionalization method solves the problem by decorating high-strength unweldable alloy powders with specially selected nanoparticles.

0 September 25, 2017
Staff

HRL Laboratories have developed a technique for successfully 3D printing high-strength aluminum alloys.

This new technique is capable of successfully 3D printing alloys such as  Al7075 and Al6061 and opens up possibilities to additively manufacture engineering-relevant alloys.

Credit: M. Durant HRL Laboratories

For the most part, these alloys have presented challenges in the past when it comes for 3D printing applications. However, HRL researchers have designed a new method that enables the high-strength aluminum alloys, as well as additional alloy families such as high-strength steels and nickel-based superalloys , to be used in 3D printing.

“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.

One of the challenges the researchers faced was cracking during the manufacturing process. Generally high-strength unweldable aluminum alloys such as Al7075 or AL6061 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 nanoparticles. 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.

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.

In order to find the right nanoparticle, the HRL team enlisted Citrine Informatics to help them sort through the myriad possible particles.

“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.”

This initiative will help further 3D printing applications for a number of different industries but could directly be used in aerospace and automotive manufacturing.

The paper 3D printing of high-strength aluminum alloys was published in Nature. Other authors on the paper were Jacob Hundley, Justin Mayer, and Tobias A. Schaedler all of HRL.

www.hrl.com


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