Fraunhofer Institute for Material and Beam Technology IWSOn-demand Grading of Grain Structure by Ultrasound Assisted AM – From Demonstration to Industrialization
Motivation
The UltraGRAIN project is a collaborative effort involving Fraunhofer IWS, Fraunhofer IAPT, and RMIT University, aimed at advancing metal additive manufacturing (AM) through innovative grain engineering techniques. Additive manufacturing is transforming global manufacturing, with a projected growth rate of 24% per year, expected to reach over US$41 billion by 2027. This growth is driven by the potential to redesign existing products and create new ones to meet future societal needs. Among the various AM technologies, laser-based processes like metal laser direct energy deposition (DED-LB/M) and Laser Powder Bed Fusion (PBF-LB/M) have gained significant acceptance in industries such as aerospace, automotive, and biomedical sectors.
The motivation for the UltraGRAIN project stems from the need to address the challenges associated with the formation of unfavorable microstructures, such as columnar grains, in metal AM. These microstructures can compromise mechanical properties, and while the reasons for their occurrence are known, optimizing AM parameters to overcome this issue has had limited success and often involves compromises.
Objectices and Approach
The project investigated the use of both ultrasounds and short-pulsed lasers to refine the obtained microstructure in DED-LB/M. Ultrasounds showed limited grain refinement capabilities as well as issues with process stability and scalability. On the contrary, the use of a secondary short-pulsed laser in DED-LB/M proved to be capable of inducing shockwaves in the melt pool that refine the obtained microstructure by affecting the solidifying metal. To unlock the full potential of localized grain engineering and industrialize the technological solution, several challenging tasks will be addressed:
- A deeper understanding of the physics of pulsed laser induced shockwaves
- Understanding how these shockwaves influence nucleation and grain growth during solidification
- Development of a simulation model to predict grain evolution
- Development of design guide lines for mechanical components that incorporate grain engineering
