Bulk metallic glass (BMG) appears to be much easier to print than traditional forms of metal. For instance, researchers have succeeded in printing BMG in a manner similar to plastic, without losing interesting properties of metal such as strength in the process.
Metal is a lot trickier to print than plastic. For instance, plastic can be heated to a temperature below which it softens but does not melt. Among other things, this allows the material to be pressed through the nozzle of a fused deposit modelling (FDM) printer using an extruder. Traditional forms of metal, however, do not reach this state, making metal printing difficult.
Unique atomic structures
BMG is a special alloy of metals that if heated do not melt, but become soft. This is interesting, as this property allows BMG to be deformed to a temperature where they have softened enough to be pressed through an extruder of a 3D printer. This allows BMG to be printed in a manner similar to plastic, something not possible with traditional forms of metal.
The material is an intermediate form between metal and glass. This is due to the atomic structure of the material. The atoms of traditional forms of metals have an ordered crystalline structure. If this material is cooled very quickly, this structure is lost and a non-crystalline microstructure, also called an amorphous structure, is created. Metals containing these properties are also called amorphous metals or metallic glass. If this material has a thickness of more than 1 millimetre, it is called BMG.
Heating to 460 °C
The research team made rods of metallic glass with a diameter of one millimetre and a length of 700 mm. These rods are heated to a temperature of 460 °C and pushed through a 0.5 mm nozzle with a force of 10 to 1,000 Newtons. Under these conditions, the metal can be printed on an FDM printer in a manner similar to printing ABS or PLA, for example.
The method was developed by a research team comprising researchers from Yale University, experts from the company Desktop Metal and researchers from MIT. The team is led by Yale University professor of mechanical engineering and materials science Jan Schroers. Schroers has been focusing on investigating BMGs for some time. In 2011, for instance, Schroers managed to use BMGs to blow perfume bottles, lenses and cylinders, among other things. This used a process similar to glass blowing.
Revolutionising additive manufacturing
The researchers expect their printing method to revolutionise additive manufacturing in metal with BMG. "In addition to prototyping, the realised properties of printed parts combined with the versatility in part design make this 3D printing technology suitable for manufacturing high-performance components for medical, aerospace and space applications," said Punnathat Bordeenithikasem, postdoctoral fellow at the NASA Jet Propulsion Laboratory at the California Institute of Technology and a recent graduate of Yale University.
More information about the 3D printing technique can be found in a paper published by the research team in ScienceDirect.
Author: Wouter Hoeffnagel
Source: Yale University
Source: ScienceDirect
Source: EurekAlert!
Source photo: Pixabay / creil91
