Towards additive manufacturing of magnesium alloys through integration of binderless 3D printing and rapid microwave sintering

Abstract 3D printing (3DP) is a two-step additive manufacturing technique (AM) in which additively manufactured green parts in the first step are transformed into functional parts during the second step. 3DP could attract more interest if a new window of opportunity for its first and second steps is opened. Here we use capillary-mediated binderless 3DP as a novel method to additively manufacture green parts of Mg-5.06Zn-0.15 Zr powder. A unified perspective on the development steps of process parameters to obtain sufficient handling strength and a high level of dimensional accuracy in the green parts without compromising its chemical composition is established by using a scanning electron microscope, X-ray micro-tomography, vibrational spectroscopy, and chemical analysis. For the first time, microwave (MW) sintering is successfully used for densification of the green parts with centimeter-scale dimensions in which the primary chemical composition of the Mg-Zn-Zr powder is retrieved from the green parts, resulting in a compositionally zero-sum AM process. It is found that swelling leads to loss of shape fidelity during MW sintering of the green parts at temperatures ≥ 510 °C. As discussed in the context of thermal and non-thermal effects, MW significantly reduced sintering time by a factor of three to four times when compared to sintering in a conventional furnace. The results of this study suggest the notion of capillary-mediated binderless 3DP as well as MW sintering as a potential alternative for the first and second steps of 3DP, respectively.