Development of a new method utilizing semi-solid aluminum wires for extrusion based additive manufacturing

Abstract

In the field of additive manufacturing (AM) technologies, the development of metal-based extrusion processes constitutes a significant industrial trend in the recent years. Respective processes are differentiated into powder bed, powder-fed and wire-fed depending on the used feedstock. Among those, powder-fed AM represents the most widely used approach, despite its physical limitations leading to intense thermal gradients and an uncontrollable defective microstructure of produced parts. In this context, extrusion-based AM using a wire semi-finished product in the semi-solid state offers a novel alternative for the direct processing of metallic alloys, avoiding the limitations mentioned. For this reason, a new method for consecutive extrusion of semi-solid AlSiMg aluminum wires has been developed at the Institute for Metal Forming (IFU, Stuttgart, Germany), particularly investigating the influence of the material´s microstructure on the process result. By modifying microstructure via heat treatment, a specific modification of the rheological material behavior can be achieved in terms of a pronounced shear-thinning characteristic, thus systematically affecting extrusion and deposition. First, an experimental setup for continuously extruding semi-sold aluminum wires was realized. Subsequently, experimental investigations were carried out on the extrusion of aluminum wires prepared via the strain induced melt activated (SIMA) process as well as untreated aluminum wires, using a conductively heated printhead concept. The objective was to determine process parameters necessary for successful extrusion and deposition of the modified aluminum material as well as the final proof of concept regarding a specific transformation of the material´s microstructure during the extrusion process.