Metal additive manufacturing (AM) received enhanced scientific and industrial importance during the last decades due to the geometrical flexibility and the reduction of development cycles of complex parts. Amongst various AM methods, Selective Laser Melting (SLM) is the most eligible technique for production of fully dense bulk material with complex geometry. The development of process-adapted novel metallic structural materials is a key for a further implementation of AM in the fields of energy, mobility, and health. In this presentation, we address the development of new Advanced High Strength Steels (AHSS), i.e. high-manganese Transformation- (TRIP) and Twinning-Induced Plasticity (TWIP) steels with outstanding mechanical properties, which are suitable for AM of lightweight lattice structures with high energy-absorption functionality. Thermodynamic simulations were used to calculate the stacking fault energies of Fe-Mn-Al-C alloys, in order to predict the occurrence of TRIP and TWIP deformation mechanisms. Subsequently, the selected alloys were additively manufactured by utilization of powder blends to produce bulk specimens and lightweight lattice structures for investigation of the microstructure and texture evolution as well as the mechanical properties.
The solidification behavior of the bulk and the thin-walled lattice structure samples was analyzed by careful characterization of the as-built microstructure, element distribution and texture using OM, SEM, TEM, EBSD, EDX, and XRD. The deformation behavior was studied using uniaxial tensile and compression testing in combination with DIC to analyze the local strain distribution. It was possible to tailor the as-built microstructure from austenitc+martensitic over fully austenitic to ferritic+austenitic. Ferrite promoted grain refinement, texture randomization, and advantageous deformation behavior of lattice structures in the two-phase (α+γ) steel. The influence of the chemical composition and process parameters on the microstructure and the related microstructure-property-relationships of bulk and lattice structure samples will be discussed.