Scientists have 3D-printed amorphous metal, also known as metallic glass, which has the potential to be used in lightweight structures, wear-resistant materials and higher strength constructions.
The team from North Carolina State University published the results in the paper ‘Additive manufacturing of an iron-based bulk metallic glass larger than the critical casting thickness’ in the journal Applied Materials Today. The technique involves printing structures by applying a laser to a layer of metal powder, which melts the powder into a solid layer that is only 20 microns thick. The platform on which the layer is built then descends 20 microns, more powder is spread onto the surface, and the process repeats itself, eventually forming a solid, metallic glass object.
Metallic glass lacks the crystalline structures of most metals and making it requires rapid cooling to retain its amorphous quality and prevent the crystalline structure from forming.
“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,” said Zaynab Mahbooba, first author of the paper and a PhD student at the university’s department of materials science and engineering.
“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.”
An object’s critical casting thickness refers to the maximum thickness of an object that can be produced; prior to this announcement, it was unknown how to produce iron alloys larger than a few millimetres thick.
“This is a proof-of-concept demonstrating that we can do this,” said Ola Harrysson, corresponding author of the paper and Edward P. Fitts distinguished professor of industrial systems and engineering at NC State.
“And there is no reason this technique could not be used to produce any amorphous alloy,” Harrysson said. “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.”