Popularly known as an important mineral for maintaining bone health, magnesium is also an attractive material for manufacturing everything from airplane parts to bone implants, thanks to its lightweight and biodegradable properties. However, the element is also highly reactive, making it difficult to fabricate related compounds using advanced technologies like additive manufacturing (AM) or 3D printing.
These challenges have led researchers to look for novel ways of applying AM protocols in the manufacturing of complex and customizable magnesium alloys. One such method is binder jet AM, which shapes powdered metals into their near-final form. Unlike fusion-based AM methods, binder jetting can be done at almost ambient temperatures. The downside, however, is that binder jetting is more time-consuming, hindering its widespread industrial adoption.
In their latest study, Mojtaba Salehi, Sharon Nai and colleagues at A*STAR’s Singapore Institute of Manufacturing Technology (SIMTech) explored alternative AM methods that are more efficient. Specifically, the team sought to shorten a lengthy post-processing step called sintering, where powdered particles are fused into a solid material through heat or pressure.
Conventional sintering involves an external source generating heat that is transferred to the material, while in another technique called microwave sintering, the material absorbs microwave energy that is then converted into heat. The team’s primary aim was to investigate if and how microwave heating shortened the sintering time of 3D printed magnesium parts, as compared to conventional sintering.
To this end, the researchers used the 3D printing method they established to manufacture magnesium alloys and then tested various sintering durations in both a conventional and a microwave furnace.
Comparing the physical, chemical, and mechanical properties of the end products, the researchers found that microwave-sintered objects could be produced three times faster than their conventionally-sintered counterparts, resulting in a nine-fold energy saving.
“Our comparative analyses of the properties and sintering mechanisms in the microwave and conventional furnaces revealed that the synergy between the post-print microwave heating and the binder-free method that we previously established to eliminate the lengthy binder removal step, could lend itself to be the fastest and greenest approach for binder jet AM,” Salehi said.
The researchers also explored the potential of using printed magnesium specimens as bone scaffolding. Intriguingly, magnesium parts sintered for 15 hours in a microwave furnace were found to have comparable interconnected pore structure and physical properties to the human cortical bone.
The team is now collaborating with research and industry partners in Singapore and Germany to develop digital manufacturing solutions for fabricating biodegradable magnesium implants. “Such an end-to-end manufacturing solution enables the fabrication of customized porous magnesium parts to revolutionize the future of magnesium alloys for implant applications,” Salehi said.
The A*STAR-affiliated researchers contributing to this research are from the Singapore Institute of Manufacturing Technology (SIMTech).