New high stiffness materials for light weight constructions using ultrafast additive manufacturing

• Applicants: Dr.-Ing. Stephanie Lippmann, since 8/2022; Professor Dr. Stefan Nolte
• Subject Area: Synthesis and Properties of Functional Materials ; Mechanical Properties of Metallic Materials and their Microstructural Origins ; Thermodynamics and Kinetics as well as Properties of Phases and Microstructure of Materials
• Term: since 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 409766389

Novel construction materials with superior stiffness combining high elastic moduli with low mass densities will be developed. The investigations on Al-Si and Al-Li started within the first project phase will be continued, now with a strong focus on Al-Li. A complete processing route starting from producing the Al-Li alloy powders without agglomeration to the production of dense LPBF Al-Li samples with enhanced properties will be established.Especially Al-Li-(Cu-Ca-Zr) alloys of significantly higher Li contents than commercial Al-Li alloys will be generated and processed, taking advantage of the rapid cooling and thus the solute trapping during the LPBF process. The LBPF applied within this project is based on ultrashort laser pulses (USP). Compared to conventional continuous wave laser systems, USP generate drastically higher thermal gradients and cooling rates. The optimization of the USP-LPBF process for reduced Li loss and enhanced mechanical properties due to alloying and optimized processing will be assisted by simulation of the laser energy deposition and in-situ monitoring of the Li loss during LPBF. During the second project period, additional in-situ measurements of the melting/solidification process in the melt pool during LPBF by employing an infrared camera, which records the temperature distribution as a function of time with high temporal and spatial resolution, will be carried out. Correlation of the temperature history with microstructural features will allow to conclude on superheating prior to resolidification. In combination with the microstructure characterization, the in-situ measurements will contribute to better understand the melting and solidification dynamics in the melt pool during LPBF.A more profound understanding of the process dynamics and microstructure formation during LPBF is expected to be reached by applying numerical models on both microscopic and macroscopic length scales. During the second period of the project, macroscopic simulations of laser energy deposition and the shape of the melt pool using a FEM model will be combined with a micromodel for the melting of powder particles and the subsequent solidification. Off-equilibrium effects, forced convection and interfacial thermodynamics will be considered. Laser processing parameters and thermal properties of powder and substrate will be correlated with the resulting microstructures. The advanced characterization techniques and the USP-LPBF will be shared with other applicants in the SPP 2122. The project will be part of the Round Robin experiment.

• DFG Programme: Priority Programmes
• Subproject of: SPP 2122: Materials for Additive Manufacturing
• Ehemaliger Antragsteller: Professor Dr. Markus Rettenmayr, until 8/2022 (†)