Additive manufacturing of magnesium
Ultimate lightweight construction and resorbable implants from the PBF-LB printer.
1. Introduction: The forgotten light metal
When it comes to additive lightweight construction, titanium and high-strength aluminum alloys dominate the discussion. But a third material is increasingly coming into focus due to its extreme physical properties: magnesium.
Magnesium is about a third lighter than aluminum and a whopping 75% lighter than steel. At the same time, it offers excellent specific strength and excellent damping properties. Metal 3D printing of magnesium offers immense potential, but presents users with enormous safety and process challenges.
The danger of printing magnesium
Magnesium powder is highly reactive and extremely flammable. In fine powder form, a minimal spark or electrostatic discharge is enough to cause a fatal dust explosion. 3D printing of magnesium therefore requires special, highly safe machine systems with strict ATEX guidelines and perfect inert gas management.
2. The PBF-LB printing process of magnesium alloys
Processing using the Laser Powder Bed Fusion (PBF-LB) process requires overcoming several metallurgical hurdles.
- Low boiling point: Magnesium has an extremely low boiling point (approx. 1,090 °C). When the laser hits the powder, it not only melts but also evaporates very quickly. This strong metal vapor ("plume") blocks the laser beam and results in an unstable melt pool. Special parameters and very high protective gas flow velocities are required.
- Oxygen affinity: Magnesium oxidizes immediately. The build chamber must be flushed with argon of the highest purity class to eliminate oxidation and the risk of fire.
- Common alloys: Frequently it is not pure magnesium that is printed, but rather alloys such as WE43 (magnesium with yttrium and rare earths) or AZ91. These alloys improve strength, reduce ignitability and increase corrosion resistance.
3. Applications in medical technology: Absorbable implants
The most exciting property of magnesium is its biocompatibility and its ability to be broken down by the human body (bio-absorbability).
While conventional titanium stents (vascular supports) or bone screws often remain in the body forever or have to be removed in a second operation, magnesium implants dissolve on their own after a defined period of time after the bone or tissue has healed. Through 3D printing (topology optimization and targeted porosity), the speed of degradation (degradation rate) of the implant in the body can be precisely controlled.
4. Applications in automotive and aerospace
Where every gram counts, magnesium is the king of metals.
- Aviation: For non-structural interior components (e.g. seat brackets, covers) where the primary aim is to drastically reduce weight to save kerosene.
- Automotive: Mounts for electronics, gearbox housings and steering wheel skeletons. In addition to its low weight, magnesium offers extremely good damping against vibrations (noise, vibration, harshness - NVH), which makes it very attractive for the e-mobility sector.
5. Conclusion: A risky but worthwhile path
The additive manufacturing of magnesium is still at an earlier stage of industrial maturity compared to aluminum or titanium. The high hurdles regarding occupational safety and handling (powder handling in an argon atmosphere, wet separators) still deter many contract manufacturers. But the incomparable advantages in medical technology (absorbable implants) and in ultimate lightweight construction guarantee magnesium a firm niche in industrial 3D printing of the future.