Investigation of in-situ precipitation behaviour in density-reduced high-strength κ-phase (Fe,Mn)3AlCx reinforced high-manganese steels (κ-HMnS) during laser-based Additive Manufacturing

• Applicants: Professor Dr.-Ing. Christian Haase; Professor Dr.-Ing. Johannes Henrich Schleifenbaum
• Subject Area: Metallurgical, Thermal and Thermomechanical Treatment of Materials
• Term: from 2020 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 439900808

Among materials for structural components with high energy absorption high manganese steels (HMnS) are a promising alloy class. Due to the activation of other plastic flow mechanisms besides dislocation glide HMnS show high strength in combination with high formability. However, despite of these outstanding properties HMnS have found only a few industrial applications. The main reasons are high costs for alloying elements and energy consuming post treatment to reduce segregation, which results from casting. Additive manufacturing (AM) offers an alternative to conventional manufacturing routes (e.g. continuous casting and subsequent forming). An interesting system is Fe-Mn-Al-C with high content of Mn (ca. 20-30 wt.-%), Al (ca. 6-12 wt.-%) and C (ca. 0.6-1.3 wt.-%). This alloy group exhibits a reduced density of approx. 6,6 g/cm3 and the potential for strengthening through the precipitation of coherent Kappa carbides. In this project the alloy X110MnAl30-8 will be processed by powder-based laser metal deposition (LMD). The main goal is to elaborate a profound understanding of the solidification and precipitation behavior as a function of process parameters, local metallurgy, rapid cooling and cycling reheating during the layer-by-layer build-up. The process parameters will be varied in reasonable limits according to the build-up of dense volumes. The analysis ranges from nano scale (fine precipitations, segregation) and micro scale (grains, layer boundaries) to macro scale (mechanical properties). By adapting relevant process parameters samples of X110MnAl30-8 with different fractions of Kappa carbides - formed during the T-t-cycles of the layerwise build-up - will be produced and analysed. The mechanical properties will be determined via hardness measurement and compressive and tensile tests. Microstructure and fracture plane analysis of the deformed samples is performed to understand deforming and failure mechanisms.

• DFG Programme: Research Grants