Semi-solid wire-feed additive manufacturing of AlSi7Mg by direct induction heating

Abstract

• Demonstration of an induction heating based additive manufacturing process. • The novel process enables high speed additive manufacturing with build rates of around 20 mm 3 /s (0.054 g/s). • Adaptation of induction power during the process allows multilayer specimen fabrication. • Defects in the novel process are analysed for the first time using µCT to pave the way for their future prevention. In this study, a novel process is presented in which direct induction heating with frequencies in the MHz range is used for the wire-feed additive manufacturing of the alloy AlSi7Mg. The high frequency of 1.5 MHz enables processing of 1.2 mm diameter wires without the need for indirect heating via a nozzle. The feasibility of the process is proven by the experimental identification of a proper process window regarding the influential parameters such as the distance between inductor and substrate, induction power and wire feed rate for the fabrication of single layers. Furthermore, a strategy for the successful fabrication of multi-layered cubes is developed. The microstructure of the cubes exhibits a characteristic variation along the build direction. Micro-computed tomography is used to reveal defects like lack of fusion and spherical pores in test cubes. The presented results are used to derive possible process improvements, which will allow the novel process to be used as a fast and powder-free alternative metal additive manufacturing route in future.