Additive Manufacturing of Magnesium Alloy WE43

Additive manufacturing (AM) of magnesium alloys for biomedical applications is of growing interest in industry due to the design possibilities for complex structures that promote the healing process and overall health of a patient. AM allows for individualized patient specific implants that are not possible to produce by traditional manufacturing. Magnesium alloys have shown promising biocompatible and mechanical characteristics. The primary advantage of magnesium is that the body can safely degrade the implant away, which minimizes or avoids long term complications associated with a foreign object in the body. Magnesium has a comparable modulus to bone that minimizes the harmful effects of stress shielding. Although magnesium is ideally suited as a biodegradable implant material, it is challenging to 3D print because of the low vaporization temperature and high reactivity in powder form that presents an explosion risk. Understanding the printability of magnesium alloys is a critical knowledge gap preventing more complex, patient specific orthopedic implants. This research focused on the viability of using two AM technologies to produce fully dense magnesium parts: powder bed fusion and directed energy deposition. Powder bed fusion utilizes stationary powder typically between 20 to 50 microns. Directed energy deposition utilizes dynamic flowing powder ranging from 50 to 100 microns. In this work, there were two research objectives: (1) determine a methodology to produce highly dense parts utilizing powder bed fusion and measure the resulting mechanical properties, and (2) determine a methodology to produce highly dense parts utilizing directed energy deposition. Results showed that a relative density greater than 99% was achievable with both AM technologies. Build plate position played an important role in the density of the printed part. For powder bed fusion, the energy density needed for fully dense parts, where no key holing or balling occurs, was between 25 J/mm3 to 75 J/mm3 . For directed energy deposition, an ideal energy density was between 126 J/cm3 to 233 J/cm3 . In summary, this work demonstrates the feasibility of producing highly dense magnesium parts using both powder bed fusion and directed energy deposition. Advisor: Michael Seal