Exciting new technique
US scientists 3-D print high-strength aluminum
Breakthrough in metallurgy: researchers at HRL Laboratories, LLC, 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 have been among thousands that were not amenable to 3D printing – a difficulty that has been solved. 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 nanoparticles.
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. 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. To find the correct nanoparticles, in this case zirconium-based nanoparticles, the HRL team enlisted an industry partner to help them sort through the myriad possible particles to find the one with the properties they needed.