Expecting to fly HRC Lab

A new process for 3D-printing things could pave the way for lighter, faster aircraft that potentially fly further on the same amount of fuel.

Today’s aeroplanes are held together with thousands of metal rivets and fasteners. That’s because the lightweight but strong aluminium alloys used for their frames are considered unweldable. Try to weld them and you get a phenomenon called hot-cracking, in which the finished alloy weakens and fractures as it cools.

This and other adverse welding effects also stand in the way of 3D-printing high-strength aluminium alloy parts. When researchers have tried, the resulting laser-fused mass flakes away at the welding area like a stale biscuit.


Yet that looks set to change soon. Researchers at HRL Laboratories in Malibu, California, seem to have overcome this long-standing problem, after developing a way to 3D-print the two most commonly used types of high-strength aluminium alloys.

These alloys are not only highly desirable for aircraft, but also for cars and trucks. In addition, the method opens up the possibility of using 3D-printing processes in a similar way to create high-strength steels and nickel-based superalloys.

Nano-coating

The team’s trick was to coat the metal particles with specially selected nanoparticles that seed and create a framework of the desired alloy microstructure as the laser-heated metal solidifies. As it cools, the molten alloy follows the crystalline pattern set by these nanoparticles, preventing hot-cracking. That means the final, manufactured part retains its full physical strength.

To find suitable nanoparticles – specifically, zirconium-based nanoparticles – the researchers sorted through the myriad possible elements on the periodic table to find the one with the right properties.

Zirconium is not particularly costly, and in this case only makes up part of each particle. The moderate manufacturing costs would be justified by the high-value applications.

Welded aluminium aircraft could lead to significantly lighter aeroplanes – and when it comes to aeroplanes, weight translates to money. A lighter frame may allow aircraft to fly further on the same amount of fuel.