The main objective of the coordinated project is the development of new metal AM processes, based on Fused Deposition Modelling (FDM) techniques, aiming at drastically reducing the price of the metal components manufactured by AM and facilitating their implantation in the aeronautics sector. In this framework, the subproject led by the Polytechnic University of Catalonia (UPC) will work on the design of a printing route based on the development of aluminium alloys ready to be printed in a 3D printer adapted to work at the temperatures for which the alloys are in a semisolid state and exhibit a thixotropic behaviour. In terms of the printing setup, some modifications will be implemented to a 3D printing machine. The modifications will affect the feeding system which will have to be able to extrude the material through the nozzle at temperatures around 600ºC. The initial concept considered consists on a heated piston similar to the paste extruders used in polymer, ceramic suspensions or food printing. The extruder will be fabricated on a material able to withstand the high temperatures and it will be heated using flexible resistances. The weight of the new extruder, heavier than the ones used for polymer systems, as well as the high temperatures required for the printing, will require modifications in the 3 axis moving system. Depending on the evolution of the project, other systems, such as the heating of the building platform or the control of the atmosphere to avoid oxidation, will be implemented in the printer. This printing system will be used to print thixotropic aluminium bars, as well as pellets of the metalpolymer mixtures. The aluminium bar with the required globular structure will be fabricated by the rheocasting route and will be reheated, inside the printing extruder, up to the semi-solid state temperature. The success of the printing operations for thixotropic aluminium alloys relies in a proper metallurgical design of the material. Parameters such as the amount, morphology and size of the globular alpha phase control de rheological behaviour of the material and will be crucial for the control of the printing operations and the quality of the printed components. With this regard, the rheology of the material will be characterize in order to guide the fabrication routes of the raw material and determine the process window for the printing operations. The main parameters to be controlled will be the working temperature, the printing speed, the diameter of the nozzle. The relationship between the diameter of the nozzle, i.e. printing accuracy, and the size of the alpha phase will be stablished. Additionally, the subproject will carry out the heat treatments on superalloys and aluminium alloys samples fabricated through 3D printing. This has been considered important to understand the sensitivity of the precipitation hardening mechanisms to the prior processing route.
Plan Estatal de Investigación Científica y Técnica y de Innovación 2017-2020
Programa Estatal de I+D+i Orientada a los Retos de la Sociedad