3D printed metallic glass alloys

North Carolina State University researchers have created amorphous metal, or metallic glass, alloys using 3D printing technology. This, the researchers say, opens the door to a variety of applications, such as more efficient electric motors, better wear-resistant materials, higher strength materials, and lighter weight structures.

Zaynab Mahbooba, Ph.D. student in North Carolina State University's Department of Materials Science and Engineering, said: “Metallic glasses lack the crystalline structures of most metals - the amorphous structure results in exceptionally desirable properties.”

Traditionally, making metallic glass requires rapid cooling to prevent the crystalline structure from forming. This meant researchers could only cast metallic glasses into small thicknesses no more than a few millimetres thick. That size limitation is called an alloy's critical casting thickness.

“The idea of using additive manufacturing, or 3D printing, to produce metallic glass on scales larger than the critical casting thickness has been around for more than a decade,” Mahbooba explained. “But this is the first published work demonstrating that we can actually do it. We were able to produce an amorphous iron alloy on a scale 15 times larger than its critical casting thickness.”

Their technique works by applying a laser to a layer of metal powder, melting it into a solid layer that is 20 microns thick. The ‘build platform’ then descends 20 microns, more powder is spread onto the surface, and the process repeats itself. Because the alloy is formed a little at a time, it cools quickly – retaining its amorphous qualities. However, the end result is a solid, metallic glass object – not an object made of laminated, discrete layers of the alloy.

Ola Harrysson, Professor of Industrial Systems and Engineering at NC State, said: “There is no reason this technique could not be used to produce any amorphous alloy. One of the limiting factors at this point is going to be producing or obtaining metal powders of whatever alloy composition you are looking for.

“For example, we know that some metallic glasses have demonstrated enormous potential for use in electric motors, reducing waste heat and converting more power from electromagnetic fields into electricity.

“And because we're talking about additive manufacturing, we can produce these metallic glasses in a variety of complex geometries - which may also contribute to their usefulness in various applications,” Harrysson concluded.

Author
Tom Austin-Morgan

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