NEW LIGHTWEIGHT ALLOYS FOR ADDITIVE MANUFACTURING A POWDER PRODUCERS APPROACH

摘要

Aluminum alloys represent an important product group for different engineering applications due to the specific characteristics of these materials. Due to the huge variety of potential alloying elements, resulting in very specific microstructures, aluminum alloys are often designed according to the needs of the application. Considering the use of powder-based processing routes, the inevitable oxide layer which acts as a sintering barrier makes the use of Al based powders challenging and puts limits to the available process routes. Powder Bed Fusion (PBF) methods offer an attractive alternative to overcome such obstacles, but for binder jetting processes the limitations on sinterability have to be kept in mind. Today only a few selected Al alloys (nearly all of the them from the Al-Si-Mg family) are used on an industrial scale in AM processes- mainly Laser Powder Bed Fusion (LPBF) processes. There is significant interest in establishing new alloys with more attractive properties compared with these current alloys. For some special applications, for instance aviation, there are high tech solutions available, but their use can be restricted by economic factors. Therefore, a lot of projects are beginning to consider the development of new Al based powders for AM. Due to the complexity of the whole AM process chain, alloy powder development projects require many different process aspects to be considered and normally cannot be done by one single partner. Beside the intelligent selection of the alloy or the alloying elements used to address special material requirements, such as weldability or microstructure development, the powder production step is an essential part of the alloy powder development. Development partners should always include the powder supplier, an experienced user of LPBF processes, and ideally an end user of the component. Academia or alloy design expertise, modelling, control software expertise, and post processing partners can also add to the success of any effort. In this presentation the basic principles and the different aspects of the powder production process will be discussed. Potential degrees of freedom to influence the microstructure and properties of the powder and the consequences which should be included from the beginning in the design process of the material will be described using an example joint research project combining all the stakeholders of the process chain. Starting with the alloy designer, the powder producer, the part designer and manufacturer, as well as the end-user of the component, a new lightweight aluminum based alloy (Custalloy®) was developed. The program started with various metallurgical considerations, followed by pilot plant runs, build jobs, and subsequent optimizations leading to Custalloy® and process parameters exhibiting strength and/or ductility optimization depending on selected processing route.